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Magnusiomyces capitatus bloodstream infection in a patient with acute monocytic leukemia: A rare case report

Summary

A 26-year-old patient with acute leukemia developed a serious fungal blood infection caused by Magnusiomyces capitatus, a rare organism found in environmental sources. The infection was confirmed using advanced molecular techniques and showed resistance to common antifungal drugs but responded to amphotericin B treatment. This case highlights how important it is for doctors to consider unusual fungi in severely immunocompromised patients and to use modern diagnostic methods for accurate identification and tailored treatment.

Background

Magnusiomyces capitatus is an emerging opportunistic pathogen that primarily infects immunocompromised individuals with hematological malignancies. In China, fewer than ten cases of invasive M. capitatus infections have been documented, creating significant gaps in clinical understanding. This dimorphic yeast requires molecular methods for definitive identification due to limitations of conventional microscopy.

Objective

To comprehensively document the clinical progression, diagnostic approaches, and therapeutic strategies of a rare M. capitatus bloodstream infection in a patient with acute monocytic leukemia. The case report aims to provide valuable insights for future clinical practice and research in non-endemic regions.

Results

Blood cultures grew yeast-like organisms on day 6, identified as M. capitatus through molecular methods. The isolate showed intrinsic echinocandin resistance but susceptibility to amphotericin B and azoles. Serial G-test levels correlated with fungemia progression and therapeutic response, rising from <40 to 2810.5 pg/mL before declining with amphotericin B treatment. The patient achieved clinical stabilization with split-dose amphotericin B therapy despite persistent neutropenia.

Conclusion

Early MALDI-TOF MS identification combined with serial β-D-glucan monitoring and tailored antifungal regimens are pivotal for improving outcomes in M. capitatus infections. Clinicians in non-endemic regions should consider rare fungi in neutropenic patients with persistent fever, and multidisciplinary efforts are needed to address epidemiological gaps and optimize therapies.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Report,
  • Source: PMID: 40703716, DOI: 10.1016/j.mmcr.2025.100718
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