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Photo Quiz: A cutaneous fungal infection with discordant biomarker results—a diagnostic challenge

Summary

This case describes a woman with advanced HIV who developed a serious fungal infection called histoplasmosis affecting her skin, lungs, and lymph nodes. Diagnosis was challenging because standard fungal blood tests came back negative, but careful examination of samples and specialized testing confirmed Histoplasma capsulatum. The patient was successfully treated with antifungal medications, highlighting the importance of not relying solely on negative tests when clinical suspicion is high.

Background

A 68-year-old woman from Cameroon with newly diagnosed HIV infection (CD4 count 10/mm³) presented with chronic vesicular skin rash and respiratory symptoms. The clinical presentation initially suggested Mpox virus infection but further investigation revealed a complex fungal infection with discordant biomarker results.

Objective

To present a diagnostic case of mucocutaneous histoplasmosis with disseminated disease in an advanced HIV patient and highlight the challenges of diagnosis when biomarkers yield conflicting results.

Results

Despite negative Histoplasma serology and beta-glucan testing, the patient was diagnosed with disseminated Histoplasma capsulatum affecting skin, lungs, and mesenteric lymph nodes. MALDI-TOF mass spectrometry confirmed H. capsulatum identification. Retrospective galactomannan testing was positive, supporting the diagnosis. Concomitant Pneumocystis jirovecii pneumonia was also identified.

Conclusion

This case demonstrates that negative biomarkers should not exclude histoplasmosis diagnosis in HIV patients from endemic areas, particularly with advanced immunosuppression. Clinical suspicion combined with culture and histopathological confirmation remains essential for accurate diagnosis of disseminated histoplasmosis.
  • Published in:Journal of Clinical Microbiology,
  • Study Type:Case Report,
  • Source: PMID: 40497721; DOI: 10.1128/jcm.02075-24
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