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

Summary

A woman with advanced HIV infection presented with skin sores and respiratory symptoms that were initially suspected to be a viral infection. Testing revealed she had histoplasmosis, a serious fungal infection caused by Histoplasma capsulatum that had spread throughout her body affecting her skin, lungs, and lymph nodes. While standard tests for this fungus were negative, other fungal markers and cultures eventually confirmed the diagnosis, and she was treated with antifungal medications.

Background

A 68-year-old woman native of Cameroon with newly diagnosed HIV infection (CD4 count 10/mm³) presented with chronic vesicular skin rash and respiratory symptoms. Initial clinical suspicion was for Mpox virus infection, but subsequent investigations revealed a complex case of fungal infection with conflicting biomarker results.

Objective

This case study presents the diagnostic challenge of identifying mucocutaneous histoplasmosis in an HIV-infected patient with disseminated disease, complicated by discordant biomarker results and the concurrent diagnosis of Pneumocystis jirovecii pneumonia.

Results

Histoplasma capsulatum was identified through culture, microscopy showing 1-3 µm thick-walled yeasts, and MALDI-TOF mass spectrometry confirmation. Initial Histoplasma serology was negative, but galactomannan antigen testing was positive (0.95). Disseminated histoplasmosis was confirmed with involvement of skin, lungs, and mesenteric lymph nodes.

Conclusion

This case demonstrates that negative Histoplasma serology should not exclude the diagnosis in advanced HIV disease, and alternative fungal biomarkers such as galactomannan antigen testing can support diagnosis. Proper specimen handling under appropriate biosafety levels and clinical correlation are essential for accurate diagnosis of histoplasmosis.
  • Published in:Journal of Clinical Microbiology,
  • Study Type:Case Report,
  • Source: PMID: 40497721, DOI: 10.1128/jcm.02075-24
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