Introduction
Advanced HIV disease remains closely associated with opportunistic infections and poor clinical outcomes, particularly in individuals with profound immunosuppression.1 Although antiretroviral therapy (ART) has significantly improved survival, disseminated fungal and non-tuberculous mycobacterial (NTM) infections continue to represent major causes of morbidity and mortality in people living with HIV.1 The coexistence of multiple opportunistic pathogens, together with immune reconstitution after ART initiation, may create substantial diagnostic and therapeutic challenges.
Talaromyces marneffei is an endemic opportunistic fungal pathogen in Asia and an important cause of disseminated infection in patients with advanced HIV disease.2 Clinical manifestations are often nonspecific, including fever, lymphadenopathy, pulmonary infiltrates, hepatosplenomegaly, and cytopenia, which may overlap with other opportunistic infections or inflammatory syndromes. In severe cases, disseminated infection may trigger hemophagocytic lymphohistiocytosis (HLH), a life-threatening hyperinflammatory condition associated with high mortality.3 Furthermore, paradoxical clinical deterioration after ART initiation may occur due to immune reconstitution inflammatory syndrome (IRIS), making it difficult to distinguish uncontrolled infection from excessive immune activation.4
Non-tuberculous mycobacteria are increasingly recognized as opportunistic pathogens in immunocompromised hosts. While disseminated disease caused by the Mycobacterium avium complex is relatively common in advanced HIV infection, infection caused by Mycobacterium colombiense, a member of the Mycobacterium avium complex first described in 2006, remains exceedingly rare, particularly in patients with HIV. Owing to the limited number of reported cases, its epidemiological characteristics, clinical spectrum, antimicrobial susceptibility, and optimal therapeutic strategies remain incompletely defined.5 Reported manifestations of M. colombiense infection include pulmonary, lymphatic, visceral, and osteoarticular involvement, but diagnosis is often delayed because conventional cultures have limited sensitivity and the clinical presentation is nonspecific.5 In addition, differentiating disseminated M. colombiense infection from other opportunistic infections or IRIS in patients receiving ART remains particularly challenging because of overlapping clinical manifestations. In recent years, metagenomic next-generation sequencing (mNGS) has emerged as an important diagnostic tool for identifying uncommon pathogens in complex infections, especially when routine microbiological methods are inconclusive.6 Unlike conventional culture-based methods, mNGS enables culture-independent detection of a broad range of pathogens from clinical specimens, facilitating the diagnosis of mixed or rare infections. However, interpretation of mNGS results should be integrated with clinical presentation, imaging findings, histopathology, and conventional microbiological testing because contamination, colonization, and the lack of antimicrobial susceptibility information may limit its standalone diagnostic value.
In addition, no standardized treatment regimen has been established for disseminated infection caused by rare NTM species. Management usually requires prolonged individualized multidrug therapy, monitoring for cumulative toxicity, potential drug–drug interactions between antimycobacterial agents, antifungal therapy, and ART, and occasionally surgical intervention for focal disease control. Evidence guiding treatment remains largely limited to case reports and small case series.
To date, only a limited number of disseminated M. colombiense infections have been reported in patients with HIV, and cases complicated by concurrent disseminated T. marneffei infection, secondary HLH, IRIS, and osteoarticular involvement are exceptionally uncommon. Here, we describe a patient with advanced HIV infection who initially presented with disseminated Talaromyces marneffei infection complicated by secondary HLH and subsequently developed disseminated Mycobacterium colombiense infection involving the liver and bone during immune reconstitution. This case addresses an important knowledge gap by illustrating the diagnostic and therapeutic complexity of multiple overlapping opportunistic infections during immune recovery and highlights the complementary role of tissue pathology and mNGS in establishing the diagnosis of rare disseminated NTM infection.
Case Presentation
Stage 1. Catastrophic Initial Presentation: Advanced Immunosuppression with Disseminated Opportunistic Infection and Secondary HLH
A 44-year-old male with hearing impairment and unknown history of chronic disease was admitted with a two-month history of recurrent fever, chills, cough, and progressively worsening abdominal pain, followed by fatigue and anorexia. On admission, physical examination revealed multiple enlarged lymph nodes in the cervical and inguinal regions, abdominal distension, and hepatosplenomegaly.
Initial HIV screening was positive and subsequently confirmed by the local Center for Disease Control. Laboratory investigations demonstrated pancytopenia and markedly elevated inflammatory markers, including IL-6 (74.13 pg/mL), IL-8 (533.35 pg/mL), IL-10 (46.26 pg/mL), interferon-γ (40.94 pg/mL), and C-reactive protein (32.17 mg/L). Liver function tests showed hypoalbuminemia (22.7 g/L), elevated aspartate aminotransferase (101 U/L), mildly elevated alanine aminotransferase (44 U/L), and markedly elevated lactate dehydrogenase (652 U/L). Chest imaging revealed scattered inflammatory infiltrates in both lungs and multiple enlarged lymph nodes in the mediastinum and supraclavicular regions (Figure 1A and B). Plasma HIV RNA was 1.8 × 106 copies/mL, and the CD4+ T-cell count was 14 cells/μL (4.79%), indicating advanced immunosuppression.
Figure 1 Serial chest CT showing pulmonary progression. Baseline chest CT demonstrating mild bilateral pulmonary infiltrates (A and B). Follow-up CT after ART initiation showing increased pulmonary opacities and lesion progression (C and D). Radiological worsening occurred despite minimal respiratory symptoms and coincided with CD4+ T-cell recovery, supporting a diagnosis of immune reconstitution inflammatory syndrome (IRIS).
Pathogen screening suggested multiple opportunistic infections. Plasma cytomegalovirus (CMV) DNA and Epstein–Barr virus (EBV) DNA were detectable at baseline, with viral loads of 1.12×104 IU/mL and 3.28×103 IU/mL, respectively. In addition, ophthalmologic evaluation revealed an isolated retinal hemorrhagic lesion in the temporal retina of the left eye, suggestive of CMV-related involvement, and antiviral therapy with ganciclovir was initiated because CMV end-organ disease could not be excluded clinically. Serum cryptococcal antigen (CrAg) testing was negative, making cryptococcal meningitis unlikely. The serum Talaromyces marneffei antigen titer was 1:5120, and the serum β-D-glucan test was markedly elevated. A previously obtained lymph node biopsy from another hospital was reviewed, and fungal granulomatous inflammation with necrosis was considered based on histopathology. Aerobic blood cultures and fungal blood cultures subsequently confirmed Talaromyces marneffei fungemia. Although plasma CMV and EBV DNA were detectable, EBER in situ hybridization was negative in both the supraclavicular lymph node specimen, and no evidence of CMV- or EBV-related visceral organ involvement was identified during subsequent diagnostic evaluation.
Antifungal therapy with liposomal amphotericin B was initiated immediately, along with broad-spectrum antibacterial therapy (meropenem). During hospitalization, the patient developed diarrhea, and stool culture revealed carbapenem-resistant Escherichia coli, for which antimicrobial therapy was de-escalated to moxifloxacin. Antiviral therapy with ganciclovir and prophylaxis with trimethoprim and sulfamethoxazole were also initiated. Dexamethasone (10 mg/m2) was administered to control persistent fever and systemic hyperinflammation while further diagnostic evaluation was underway.
Despite antifungal therapy, the patient developed persistent fever, progressive pancytopenia, and hepatosplenomegaly. Serum ferritin was markedly elevated (23,843.9 ng/mL). Bone marrow aspiration demonstrated hemophagocytosis (Figure 2). Based on HLH-2004 diagnostic criteria, the patient met multiple criteria including persistent fever, splenomegaly, cytopenia, hyperferritinemia, and hemophagocytosis in bone marrow, leading to a diagnosis of secondary hemophagocytic lymphohistiocytosis (HLH), likely triggered by severe disseminated infection.
Figure 2 Bone marrow smear showing hemophagocytosis. Bone marrow smear demonstrating hemophagocytic activity (A and B). Reticulohistiocytic cells are seen phagocytosing hematopoietic elements, with relatively organized cell distribution, supporting the presence of hemophagocytosis in a representative field (A). A higher-power or more representative field shows a clearly identifiable macrophage with distinct cellular borders and multiple ingested blood components, including platelets and hematopoietic cells within the cytoplasm. The phagocytic structures are centrally located and clearly visualized, providing strong morphological evidence of hemophagocytosis (B). Together, the two fields demonstrate consistent hemophagocytic activity across different microscopic views, confirming that the observed phenomenon is not incidental but a reproducible finding, supporting the diagnosis of hemophagocytic lymphohistiocytosis (HLH) in the appropriate clinical context.
Given the severity of the condition and the high suspicion of infection-triggered HLH, immunomodulatory therapy was initiated with ruxolitinib (15 mg twice daily) in combination with ongoing dexamethasone (10 mg/m2). This regimen was selected to control hyperinflammation while minimizing further immunosuppression in the setting of active disseminated infection. Concurrent antifungal therapy and supportive care were continued. Following combined antimicrobial and immunomodulatory therapy, inflammatory markers gradually decreased and hematological parameters stabilized.
After control of fungemia, antiretroviral therapy (bictegravir/emtricitabine/tenofovir alafenamide [BIC/FTC/TAF]) was initiated approximately two weeks after admission. The patient was discharged on maintenance therapy including itraconazole, ganciclovir, trimethoprim, sulfamethoxazole, and antiretroviral therapy.
Stage 2. Paradoxical Clinical and Radiological Deterioration After ART Initiation: Suspected Immune Reconstitution Inflammatory Syndrome
Approximately one month after ART initiation, follow-up chest CT showed progression of pulmonary lesions despite the absence of significant respiratory symptoms (Figure 1C and D). At readmission, the patient developed recurrent fever with a maximum temperature of 38.8°C, which was temporarily relieved with indomethacin. Repeat immunological evaluation demonstrated evidence of immune recovery, with the CD4+ T-cell count increasing to 104 cells/μL (14.08%). Although systemic inflammatory markers had decreased compared with baseline (CRP, 5.59 mg/L; IL-6, 4.04 pg/mL), the coexistence of paradoxical radiological progression and immune recovery raised strong suspicion for immune reconstitution inflammatory syndrome (IRIS). The diagnosis was supported by the temporal relationship with ART initiation, immunological recovery, paradoxical worsening of pre-existing lesions despite appropriate antimicrobial therapy, and the absence of evidence suggesting treatment failure of the initial disseminated Talaromyces marneffei infection. Corticosteroid therapy with dexamethasone was initiated and subsequently adjusted according to clinical response to control the excessive inflammatory reaction. Antiretroviral therapy was continued without interruption.
During this hospitalization, the patient developed two new subcutaneous masses on the left lower abdomen and left forearm. Abdominal CT revealed multiple low-density lesions in the liver, suggestive of infectious lesions. Contrast-enhanced MRI indicated multiple liver abscesses (Figure 3A and B). Ultrasound-guided liver biopsy was performed for pathogen identification and histopathological evaluation. Metagenomic next-generation sequencing (mNGS) of the liver biopsy tissue detected Mycobacterium colombiense at the species level, with 5 sequence reads.
Figure 3 MRI and liver biopsy suggesting multiple hepatic abscesses. Magnetic resonance imaging (MRI) of the liver (A and B). T2-weighted imaging shows lesions with central high signal intensity and a mildly hyperintense peripheral rim (A). The suspected abscess lesions are highlighted by Orange boxes (A). Diffusion-weighted imaging (DWI) demonstrates corresponding lesions with central high signal and slightly increased peripheral signal, suggesting restricted diffusion consistent with abscess formation (B). The corresponding lesions are highlighted by green boxes (B). Histopathological examination of liver biopsy shows coagulative necrosis with inflammatory fibrous tissue proliferation (C–E). Special staining reveals rare fungal organisms, suggesting possible Talaromyces marneffei infection in the appropriate clinical context.
At this stage, antimicrobial therapy was adjusted. The mNGS finding provided species-level molecular identification of M. colombiense, while the accompanying histopathological findings supported an infectious process. Based on the overall clinical and microbiological findings, combination anti-NTM therapy was initiated with azithromycin, levofloxacin, and amikacin, followed by regimen optimization with ethambutol, rifabutin, and linezolid during subsequent treatment, while corticosteroids were continued to control the inflammatory response associated with IRIS.
Approximately 2 weeks later, the patient was readmitted because of recurrent fever accompanied by nausea and vomiting. Follow-up abdominal CT showed progression of the hepatic lesions, with enlargement of some existing lesions and development of new lesions. A second ultrasound-guided liver biopsy was therefore performed, and the tissue specimen was submitted for mNGS and histopathological examination. Histopathological examination demonstrated necrosis and granulomatous inflammation, with positive acid-fast staining, providing independent evidence of mycobacterial infection. mNGS of the second liver biopsy specimen again detected Mycobacterium colombiense, with 14 sequence reads. The repeated species-level detection of M. colombiense in liver tissue at two separate time points, together with the compatible histopathological findings and acid-fast staining, provided convergent evidence supporting persistent M. colombiense infection.
Histopathology of liver tissue showed coagulative necrosis and inflammatory fibrous tissue proliferation (Figure 3C–E). Special stains demonstrated a small number of fungal elements and acid-fast bacilli. Tuberculosis Polymerase Chain Reaction (PCR) was negative, supporting non-tuberculous mycobacterial infection rather than Mycobacterium tuberculosis. These findings suggested mixed pathology involving residual fungal infection and newly identified NTM infection under immune reconstitution conditions.
Despite microbiological control of the initial fungal infection, the patient developed new inflammatory lesions and radiological progression after ART initiation, which could not be fully explained by uncontrolled infection alone. Taken together, the temporal association with ART initiation, recurrent fever, immunological recovery, paradoxical radiological progression, the development of new hepatic and subcutaneous lesions, and subsequent tissue identification of Mycobacterium colombiense supported the diagnosis of unmasking IRIS associated with disseminated M. colombiense infection (Figure 4).
Figure 4 Dynamic Changes in CRP and CD4+ T-Cell Count During the Clinical Course. Serial measurements of C-reactive protein (CRP) and peripheral CD4+ T-cell count throughout the patient’s clinical course. At initial presentation, CRP levels were markedly elevated in the setting of disseminated Talaromyces marneffei infection and secondary hemophagocytic lymphohistiocytosis (HLH). Following antifungal therapy and immunomodulatory treatment, inflammatory markers initially decreased. After initiation of antiretroviral therapy (ART), progressive recovery of CD4+ T-cell count was observed, accompanied by recurrent elevations in CRP and radiological progression, consistent with immune reconstitution inflammatory syndrome (IRIS) and subsequent unmasking of disseminated Mycobacterium colombiense infection. After initiation and adjustment of prolonged multidrug anti-NTM therapy combined with anti-inflammatory treatment, CRP levels gradually normalized while CD4+ T-cell counts remained stable during follow-up.
Stage 3. Diagnostic Reframing Following Pathogen Identification: Unmasking Disseminated Non-Tuberculous Mycobacterial Infection
Following identification of Mycobacterium colombiense, the treatment strategy shifted toward individualized long-term multidrug anti-NTM therapy while continuing ART and antifungal therapy. During this period, inflammatory markers gradually decreased and liver enzymes improved, reflecting an initial clinical response to the optimized antimicrobial regimen. Although hematologic toxicity and gastrointestinal intolerance required repeated dose adjustments, the patient remained clinically stable after individualized modification of the antimicrobial regimen. Serial imaging showed gradual reduction and stabilization of hepatic lesions rather than rapid resolution, suggesting the slow but sustained therapeutic response characteristic of disseminated NTM infection. No new visceral organ involvement was identified during this stage of treatment, indicating partial microbiological and clinical control despite the persistent chronic course of disseminated NTM infection. Continuous multidrug therapy and close clinical surveillance were therefore maintained.
This stage represented a critical diagnostic reframing process, in which the clinical focus shifted from fungal infection and HLH toward chronic disseminated NTM infection occurring in the context of immune reconstitution. Although systemic inflammatory activity gradually subsided, the persistent nature of disseminated NTM disease necessitated prolonged antimicrobial therapy and ongoing follow-up because delayed or newly apparent focal lesions could still occur.
Stage 4. Chronic Dissemination with Osseous Involvement: Surgical Intervention and Long-Term Multidrug Therapy
During continued multidrug therapy, several months later, the patient developed progressive swelling and pain in the left foot, which worsened with activity and did not improve with conservative treatment. Imaging studies suggested possible osteomyelitis involving the talus and surrounding soft tissues (Figure 5). Given persistent local symptoms, progressive radiological abnormalities, and suspected focal infection, surgical debridement and lesion excision with flap reconstruction were performed to obtain adequate source control and tissue for definitive microbiological diagnosis.
Figure 5 MRI of left foot showing lesions on sagittal and coronal images. Sagittal imaging demonstrates a patchy hyperintense lesion involving the fifth metatarsal with surrounding soft-tissue swelling. The lesion area is highlighted by yellow boxes in both sagittal (A) and coronal (B) images, consistent with active inflammatory or infectious involvement (A). Coronal imaging shows the corresponding lesion in the fifth metatarsal with similar signal abnormality and adjacent soft-tissue edema, also highlighted by yellow boxes (B), confirming the extent of disease involvement across imaging planes.
Metagenomic sequencing of surgical tissue again detected Mycobacterium colombiense with 34 sequence reads, providing additional molecular evidence consistent with persistent disseminated NTM infection with osteoarticular involvement. GeneXpert testing for Mycobacterium tuberculosis was negative.
Postoperatively, the patient continued long-term individualized multidrug anti-NTM therapy. Surgery was considered an adjunctive measure to reduce local pathogen burden rather than a replacement for systemic therapy. The antimicrobial regimen was adjusted according to treatment tolerance and the patient’s clinical response during follow-up. At the latest follow-up, the CD4+ T-cell count had increased to 120 cells/μL (24.48%), indicating sustained immune recovery. The patient remained clinically stable with good wound healing, stable liver function and inflammatory markers, and no evidence of further progression of bone lesions or new visceral involvement.
Discussion
Disseminated Opportunistic Infections and Immune Dysregulation in Advanced HIV Infection
Advanced HIV infection remains strongly associated with severe opportunistic infections and dysregulated inflammatory responses, particularly in individuals presenting with profound CD4⁺ T-cell depletion.7 Disseminated Talaromyces marneffei infection is a major opportunistic mycosis in Asia and is associated with high mortality in patients with advanced immunosuppression.2 In addition to direct infectious injury, overwhelming immune activation may trigger secondary hemophagocytic lymphohistiocytosis (HLH), a hyperinflammatory syndrome characterized by excessive cytokine release, cytopenia, hepatosplenomegaly, and multiorgan dysfunction.8 In the present case, the patient fulfilled multiple HLH-2004 diagnostic criteria, including persistent fever, splenomegaly, pancytopenia, hyperferritinemia, and hemophagocytosis in bone marrow aspirate, supporting a diagnosis of infection-associated secondary HLH. Early initiation of antifungal therapy combined with immunomodulatory treatment contributed to stabilization of systemic inflammation and hematologic abnormalities. This case illustrates the profound immune dysregulation associated with advanced HIV infection, in which severe opportunistic infection, excessive inflammatory activation, and subsequent immune reconstitution may occur sequentially or overlap, creating substantial diagnostic and therapeutic challenges.
Diagnostic Challenges of Disseminated Non-Tuberculous Mycobacterial Infection
Non-tuberculous mycobacteria (NTM) are increasingly recognized in people living with HIV, especially following immune restoration after ART initiation.1 However, disseminated infection caused by Mycobacterium colombiense, a rare member of the Mycobacterium avium complex (MAC), remains uncommon and may easily be overlooked because of nonspecific clinical manifestations and limited microbiological yield.5 First described in 2006, M. colombiense is a slow-growing NTM species within the MAC that has predominantly been reported in immunocompromised individuals, particularly those with advanced HIV infection.9 Reported clinical manifestations include pulmonary, lymphatic, bloodstream, hepatic, and osteoarticular involvement, but no characteristic clinical or radiological features have been identified, making early diagnosis particularly challenging.10 In this patient, hepatic lesions initially raised concern for persistent fungal infection, IRIS, drug resistance, or mixed infection. Conventional microbiological cultures did not identify M. colombiense. Liver tissue mNGS subsequently identified M. colombiense at the species level, with 5 sequence reads. Approximately 2 weeks later, because of recurrent fever and progression of the hepatic lesions, a second liver biopsy was performed, and mNGS again detected M. colombiense, with 14 sequence reads. Histopathological examination of the second biopsy demonstrated necrosis and granulomatous inflammation, with positive acid-fast staining, providing independent evidence of mycobacterial infection. The repeated species-level detection of M. colombiense in liver tissue at two separate time points, together with the compatible pathological findings and acid-fast staining, provided convergent evidence supporting M. colombiense infection. However, because culture isolation and independent species-level microbiological confirmation were not obtained, the molecular findings should be interpreted in the context of the overall clinical, radiological, and pathological findings. Previous studies have shown that molecular diagnostic approaches such as mNGS can significantly improve pathogen detection in complex infections when routine microbiological methods are inconclusive.6 In this case, tissue-based mNGS provided species-level identification directly from clinically involved tissue and contributed to the timely recognition of an uncommon NTM pathogen, allowing initiation of targeted anti-NTM therapy.
Nevertheless, mNGS also has important limitations. Detection of microbial nucleic acids does not necessarily distinguish active infection from colonization or contamination, and mNGS cannot routinely provide antimicrobial susceptibility information. Culture remains an important method for species identification and susceptibility testing of NTM. However, in a retrospective series of nine patients with disseminated M. colombiense infection, M. colombiense was detected by both mNGS and culture in four patients, whereas it was detected only by mNGS in the remaining five patients, indicating that culture may not always yield the organism in disseminated M. colombiense infection.11 In addition, mNGS does not provide the same level of genomic characterization as whole-genome sequencing (WGS). Therefore, although repeated detection of M. colombiense in two liver biopsy specimens strengthened the microbiological evidence, culture-based isolation, independent species confirmation, antimicrobial susceptibility testing, and genomic-level characterization were unavailable in this case. mNGS results should always be interpreted in conjunction with clinical manifestations, imaging findings, histopathology, and conventional microbiological investigations.10
This case further emphasizes the importance of tissue-based molecular diagnostics in immunocompromised hosts with atypical organ involvement. For patients with persistent or newly developed focal lesions despite appropriate antimicrobial therapy, early tissue biopsy combined with molecular diagnostic techniques may facilitate identification of uncommon opportunistic pathogens and help avoid delays in diagnosis and treatment.
IRIS and Coexistence of Persistent Infection During Immune Recovery
Immune reconstitution inflammatory syndrome (IRIS) represents an exaggerated inflammatory response occurring after initiation of ART and is particularly common in patients with advanced HIV disease and severe baseline immunosuppression.12 Differentiating IRIS from uncontrolled infection is clinically challenging because both may present with fever, enlarging lesions, and radiologic progression. Current diagnostic approaches emphasize the temporal relationship with ART initiation, evidence of immune recovery, paradoxical clinical or radiological deterioration despite appropriate antimicrobial therapy, and exclusion of alternative explanations such as treatment failure or a newly acquired infection.13,14 In this case, the temporal association with ART initiation, rising CD4⁺ T-cell count, worsening inflammatory lesions, and paradoxical clinical deterioration together with the marked decline in plasma HIV RNA following ART supported the diagnosis of IRIS. Furthermore, the initial disseminated Talaromyces marneffei infection had shown microbiological and clinical improvement after antifungal therapy, making progression of the primary fungal infection less likely. Nevertheless, persistent and newly identified pathogens were simultaneously present, including residual T. marneffei infection and disseminated NTM disease. This overlap highlights that IRIS and active infection are not mutually exclusive processes but may coexist during immune recovery.15 In the present case, liver tissue mNGS subsequently identified M. colombiense, indicating that immune restoration likely unmasked a previously unrecognized disseminated NTM infection while inflammatory responses further amplified the clinical manifestations.10 Careful balancing of antimicrobial therapy and anti-inflammatory treatment was therefore required throughout the disease course.
Therapeutic Complexity and Long-Term Management of Disseminated M. colombiense Infection
Currently, there is no standardized antimicrobial regimen specifically established for disseminated M. colombiense infection.5 Most reported cases have been managed using individualized multidrug strategies extrapolated from treatment principles for MAC disease.1,5 Accordingly, treatment in the present case was individualized on the basis of published experience with disseminated MAC infection, disease severity, organ involvement, treatment tolerance, and the patient’s clinical response.16 In the present case, prolonged combination therapy including macrolides, fluoroquinolones, rifabutin, linezolid, aminoglycosides, ethambutol, and clofazimine was repeatedly adjusted according to drug toxicity, hematologic tolerance, gastrointestinal adverse effects, and clinical response. Because prolonged multidrug therapy in patients receiving ART is frequently complicated by hepatotoxicity and clinically significant drug–drug interactions, particularly between rifamycins and antiretroviral agents, close monitoring of liver function and individualized adjustment of antimicrobial regimens were essential throughout treatment.16 Serial imaging demonstrated gradual stabilization rather than rapid resolution of hepatic lesions, consistent with the chronic and slowly responsive nature of disseminated NTM infection.
An additional notable feature of this case was osteoarticular dissemination involving the foot and talus, with M. colombiense detected by mNGS in the surgical tissue, further supporting osteoarticular involvement. Skeletal involvement by rare NTM species is infrequently reported and may indicate prolonged hematogenous dissemination in severely immunocompromised individuals.5 Surgical debridement served as an important adjunctive intervention to reduce local pathogen burden and preserve function, while systemic multidrug antimicrobial therapy remained the cornerstone of treatment. This case also highlights the importance of combining surgical intervention with prolonged antimicrobial therapy for selected patients with localized osteoarticular disease that persists despite appropriate medical treatment. Together, this case underscores the importance of individualized long-term management and multidisciplinary care in rare disseminated NTM infections complicating advanced HIV disease.
Comparison with Previously Reported Cases
Compared with previously reported HIV-associated Mycobacterium colombiense infections, the present case demonstrated several distinctive clinical features. Most published cases have described isolated pulmonary disease, lymphadenitis, or disseminated infection without the coexistence of multiple severe opportunistic complications.10 In contrast, our patient experienced a highly complex clinical course characterized by disseminated Talaromyces marneffei infection, secondary hemophagocytic lymphohistiocytosis (HLH), immune reconstitution inflammatory syndrome (IRIS), hepatic involvement with M. colombiense detected by tissue mNGS, and subsequent osteoarticular dissemination with M. colombiense detected in surgical tissue, further supporting osteoarticular involvement. To our knowledge, this combination of sequential opportunistic infections and immune-mediated complications has rarely been documented in the published literature.9
Another notable feature of this case was the pivotal role of tissue-based metagenomic next-generation sequencing in establishing the diagnosis after conventional microbiological investigations failed to identify the causative pathogen. Repeated detection of M. colombiense from both liver biopsy and surgical tissue further strengthened the microbiological diagnosis and guided individualized long-term antimicrobial therapy. These findings highlight the complementary value of molecular diagnostics and histopathological evaluation in immunocompromised patients with persistent or atypical lesions.6 To our knowledge, reports describing this constellation of disseminated M. colombiense infection, T. marneffei coinfection, secondary HLH, IRIS, and osteoarticular involvement remain exceptionally rare.
Clinical Implications and Limitations
This case highlights several important clinical implications. First, clinicians should maintain a high index of suspicion for uncommon opportunistic pathogens in patients with advanced HIV infection who develop persistent or newly emerging lesions despite appropriate antimicrobial therapy. Second, tissue biopsy combined with molecular diagnostic techniques, particularly metagenomic next-generation sequencing, can substantially improve pathogen identification when conventional microbiological methods are inconclusive, thereby facilitating timely and targeted treatment.6 Finally, successful management of complex disseminated infections often requires prolonged individualized antimicrobial therapy, careful monitoring for drug toxicity and drug–drug interactions, and close collaboration among infectious disease specialists, microbiologists, pathologists, radiologists, and surgeons.
This report also has several limitations. As a single-case report, our findings cannot be generalized to all patients with disseminated M. colombiense infection. Although M. colombiense was repeatedly detected at the species level by tissue-based mNGS in two liver biopsy specimens obtained at separate time points, and supported by histopathological findings and acid-fast staining, culture isolation of M. colombiense and independent species-level microbiological confirmation were not obtained. The repeated detection of the same organism in liver tissue at separate time points strengthened the microbiological evidence; however, these molecular findings cannot be considered equivalent to culture-based or independent species-specific confirmation. WGS was not performed in this case. Therefore, genomic-level confirmation, strain-level characterization, and molecular epidemiological analysis could not be performed, and no conclusions regarding these aspects can be drawn from the available data. In addition, antimicrobial susceptibility testing was not performed because no viable isolate was obtained from the liver biopsy tissue for subsequent culture and susceptibility testing. Treatment selection and subsequent modifications were based on published experience with disseminated MAC disease, the patient’s clinical response, and treatment tolerance rather than organism-specific susceptibility results.16 The lack of susceptibility data is therefore an additional limitation in assessing the optimal antimicrobial regimen for this patient. Nevertheless, the repeated detection of M. colombiense in clinically involved tissue specimens, together with compatible histopathological, acid-fast staining, radiological, and clinical findings, provided convergent evidence supporting the diagnosis, while the absence of culture isolation and independent species confirmation should be recognized as an important limitation. The detailed longitudinal clinical course, repeated microbiological confirmation, and multidisciplinary management provide valuable insights into the diagnosis and treatment of this rare opportunistic infection in advanced HIV disease.
Conclusion
In summary, this case highlights that disseminated Mycobacterium colombiense infection can present with involvement of deep visceral organs such as the liver and extend to osteoarticular sites in people living with HIV with advanced immune suppression (Figure 6). This case also illustrates the diagnostic complexity arising from the coexistence of disseminated opportunistic infection, secondary hemophagocytic lymphohistiocytosis (HLH), and immune reconstitution inflammatory syndrome (IRIS), which may obscure recognition of rare non-tuberculous mycobacterial (NTM) disease. Rare NTM species should be considered in the differential diagnosis when systemic lesions persist despite standard therapy for common opportunistic pathogens. Early utilization of molecular diagnostic tools, including metagenomic next-generation sequencing (mNGS), may facilitate pathogen identification when conventional methods are unrevealing, enabling targeted antimicrobial therapy. Prolonged, individualized multidrug regimens tailored to clinical response and tolerance may lead to sustained clinical improvement. In cases with focal skeletal involvement, surgical intervention should be considered as an adjunct to systemic therapy to achieve local disease control and preserve function. This case further emphasizes the importance of a multidisciplinary approach integrating clinical assessment, imaging, histopathology, and molecular diagnostics to optimize the management of complex opportunistic infections in advanced HIV disease. Given the absence of standardized treatment guidelines for rare disseminated NTM disease, further accumulation of case data and susceptibility profiles is necessary to refine evidence-based management strategies.
Figure 6 Timeline of clinical course, diagnostic workup, and therapeutic interventions for disseminated Mycobacterium colombiense infection. Red text indicates major clinical events and disease progression. Blue text indicates diagnostic findings, and green text indicates therapeutic interventions. Arrows indicate changes in HIV viral load and CD4⁺ T-cell count, with upward arrows indicating an increase and downward arrows indicating a decrease.
Abbreviations
ART, Antiretroviral therapy; CMV, Cytomegalovirus; CT, Computed tomography; EBV, Epstein–Barr virus; HLH, Hemophagocytic lymphohistiocytosis; HIV, Human immunodeficiency virus; IRIS, Immune reconstitution inflammatory syndrome; MAC, Mycobacterium avium complex; mNGS, Metagenomic next-generation sequencing; NTM, Non-tuberculous mycobacteria; PCR, Polymerase chain reaction; MRI, Magnetic resonance imaging; WGS, whole-genome sequencing.
Data Sharing Statement
All data generated or analyzed during this study are included in this published article.
Ethics Approval and Consent to Participate
This case report was conducted in accordance with the ethical principles of the 1975 Declaration of Helsinki. The research protocol was approved by the Institutional Review Committee of The First Affiliated Hospital, Zhejiang University School of Medicine (FAHZU) (approval number: 2022-936). No additional institutional approval was required for publication of this individual case report. Written informed consent was obtained from the patient for participation in the study and use of relevant clinical information. All data used for analysis were anonymized.
Consent for Publication
Written informed consent was obtained from the patient for the publication of this case report and any accompanying images.
Acknowledgments
We express our sincere gratitude for the unwavering trust bestowed upon our medical team by the patient throughout the entire treatment process.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Funding
This work is supported by Prevention and Control of Emerging and Major Infectious Diseases-National Science and Technology Major Project (2025ZD01905200).
Disclosure
The authors declare no competing interests.
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