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Description
A 41-year-old HIV-infected woman presented with prolonged fever at another hospital. Besides low CD4 count (8 cell/mm3) and pancytopaenia, blood cultures, chest radiograph, chest–whole abdominal CT and bone marrow examination were unremarkable. Empirical treatment for tuberculosis was given. One week later, she developed rash and was transferred to our hospital. Physical examination showed multiple pruritic erythematous purplish maculopapular rashes with central necrotic areas predominantly on face, back-chest wall and both forearms (figure 1). Peripheral blood smear (figure 2) and skin scraping (figure 3) revealed multiple intracellular yeast-like organisms suggestive of Histoplasma capsulatum. Intravenous amphotericin B was given, followed by oral itraconazole. Her condition improved after 2 weeks of treatment. Antiretroviral medications were initiated 1 month later.
Multiple pruritic erythematous purplish maculopapular rashes with some central necrotic areas predominantly on the (A) face, (B) back-chest wall and (C,D) both forearms.
Peripheral blood smear (Wright stain, 1000×) revealed multiple intracellular yeast-like organisms in leucocytes.
Skin scraping (Wright stain, 1000×) revealed multiple intracellular yeast-like organisms.
As clinical manifestations of disseminated histoplasmosis are usually non-specific,1 high suspicion is important. Classical techniques for diagnosis include culture, microscopy and antigen/antibody detection. Culture is a gold standard that requires a significant amount of time so the other types of investigations are required before an empirical treatment is given. Microscopy has about 42% sensitivity2 and its accuracy depended on experience of clinicians and laboratory staff. H. capsulatum have a long incubation period (2–4 weeks), while duration of microscopy or antigen/antibody detection is short (1–2 hours). Antigen detection in a disseminated disease provides the highest sensitivity (urine, 92%).2 Positive yield of test in immunocompromised patients will increases due to high burden of organisms (94.6% in AIDS vs 73.3% in immunocompetent).3 Sensitivity of antibody detection is around 71% and decreases in immunocompromised patients because of poor immunity (positive yield 78.9% in AIDS vs 88.9% in non-immunocompromised).3
False-positive result of antigen/antibody detection is possible in patients with other fungal infections or asymptomatic individuals in an endemic area. Specificity of antigen/antibody detection ranges for 85%–96% and 39%–100%, respectively.2 3 Skin test has been less commonly performed at bedside because of the cross-reactivity with other fungi and low sensitivity in ill patients.3 In summary, microscopy is a non-invasive test that could be rapidly performed despite low sensitivity. A positive microscopic finding could help to choose the empirical treatment while waiting for a more definitive test result.
Learning points
Disseminated histoplasmosis presents with non-specific signs and symptoms. Awareness of this disease should be emphasised.
Despite relatively low sensitivity, a peripheral blood smear is a simple bedside investigation that must be carefully examined in febrile HIV-infected patients with non-specific signs and symptoms.
Acknowledgments
We thank Medical Technologist Reference Laboratory, Bamrasnaradura Infectious Disease Institute for assistance with laboratory processes in this case.
Footnotes
Contributors PB, WP and PS wrote the manuscript. All the authors treated the patient, contributed to the conception of the work, reviewed the manuscript and gave final approval of this article.
Competing interests None declared.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.