A 2-year-old boy receiving cancer treatment for rhabdomyosarcoma with lung metastases developed disseminated Mycobacterium xenopi infection, according to a case report describing an unusual pediatric oncology presentation. The child developed persistent fever and widespread nodular lesions involving multiple organs. Although the lesions initially appeared on positron emission tomography-computed tomography and prompted resumption of chemotherapy for suspected cancer progression, subsequent surgery and microbial testing instead identified a slow-growing nontuberculous mycobacterium.

The diagnostic course was complicated by the simultaneous detection of Candida albicans. Fungal staining and metagenomic next-generation sequencing identified the yeast, but the patient showed little clinical improvement after antifungal treatment. A lung wedge resection then revealed chronic necrotizing granulomas containing acid-fast bacilli, a finding consistent with mycobacterial infection. Metagenomic next-generation sequencing of the sampled material confirmed M. xenopi, a slow-growing nontuberculous mycobacterium known to cause opportunistic pulmonary and disseminated disease in immunocompromised people. Documented disseminated infections attributable to this species are particularly uncommon in children.

The case illustrates how a new pulmonary lesion in a child undergoing oncology treatment can have more than one explanation. The hypermetabolic lesion detected by PET-CT was interpreted as possible disease progression, and chemotherapy was resumed, but the subsequent appearance of nodular lesions in several organs and the limited response to antifungals prompted further investigation. The lung specimen provided tissue-level evidence of infection: necrotizing granulomatous inflammation with acid-fast organisms, followed by molecular identification of M. xenopi. The report does not establish that the concurrent Candida albicans finding represented a second confirmed invasive infection, although the authors considered the possibility of combined infection.

After anti-nontuberculous mycobacterial therapy began, the child’s fever subsided rapidly. The regimen consisted of linezolid, rifampin and clarithromycin and was administered for six months. At the latest follow-up reported in the case, all of the identified nodules had either partially or completely regressed. This outcome was observed in a single patient and does not establish the effectiveness of the regimen for other children or adults. The case report instead documents a rare manifestation of disseminated M. xenopi infection, a diagnostic overlap between cancer progression and opportunistic infection, and the value of examining tissue when noninvasive or initial microbiological findings do not explain the clinical course.

Because this was a case report, the evidence is limited to one pediatric oncology patient and cannot determine how frequently M. xenopi causes disseminated infection in children, whether the concurrent fungal finding was clinically important, or how outcomes compare with other treatment strategies. Nevertheless, the findings offer a clinically detailed example of persistent fever, multifocal nodules and necrotizing granulomas arising during cancer therapy. The investigators’ proposed combination of tissue sampling, acid-fast staining and metagenomic sequencing helped resolve an infection that initially resembled progression of the underlying malignancy, while subsequent imaging showed partial or complete regression of the nodules after six months of targeted antimicrobial treatment.

Subject of Research: Disseminated Mycobacterium xenopi infection in a child receiving cancer treatment

Article Title: Disseminated Mycobacterium xenopi infection in a pediatric oncology patient: case report

Article References: Lin, S., Li, L., Chen, J., Tao, Z., & Mao, J. (2026). Disseminated Mycobacterium xenopi infection in a pediatric oncology patient: case report. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14380-6

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14380-6

Keywords: Mycobacterium xenopi, pediatric oncology, nontuberculous mycobacteria, disseminated infection, metagenomic sequencing, granulomatous inflammation, rhabdomyosarcoma, case report, Disseminated, Mycobacterium, xenopi, infection