Thank you to Kendra M and Annie Luetkemeyer for discussing the case of women with HIV/AIDS and disseminated histoplasmosis, manifesting as a diffuse papular rash and diffuse lymphadenopathy. We learned some great information about etiology, diagnostics, and classic presentations of histoplasmosis.
- Most common endemic mycosis in patients with HIV/AIDS; overall declining though in HIV positive patients given success with ART.
- Inhaled from soil that contains bird and bat droppings.
- In the US, classically thought about in the Mississippi, Ohio and St Lawrence River valleys. In this hemisphere, also seen in Caribbean and Central America.
- Worldwide, Histo has been found in all continents except for Antarctica!
Histo: Clinical presentation
Both immunocompetent and immunocompromised hosts can have histoplasmosis infection
- Immunocompetent host – usually presents as a mild pulmonary infection
- Immunocompromised host – especially with advanced AIDS (and CD4 less than 200), can have systemic multi organ involvement.
- Systemic: Fever and weight loss very common in disseminated histoplasmosis
- Cutaneous: 10-15% of pts with disseminated histo have skin involvement, usually nodules and papules diffusely
- Gastrointestinal disease: 70% of pts with disseminated histo have GI involvement; lesions include ulcers most often in colon or ileum.
- Hepatic and splenic involvement : infiltrative liver disease
- Pulmonary: productive cough, apical infiltrates with cavitation
- CNS: 5-20% of cases, meningitis or focal brain lesions
- Common laboratory signs
- Pancytopenia – can infiltrate bone marrow
- Isolated elevated alk phos – infiltrative liver picture
- Ferritin – frequently very elevated in s/o histo infection
How to diagnoses Histoplasmosis
- Big picture: maintain high clinical suspicion, as may have false negatives in multiple modalities of testing for histoplasmosis.
- Top three tests for Histo diagnosis:
- Antigen testing: Urine Histo Ag: 75% sensitive in nonimmunocompromised, and 95% sensitive in immunocompromised.
- Biopsy of involved organs with PAS stain.
- Antibody testing: immunodiffusion test and complement fixation are ~90% sensitive in immunocompetent, ~70% sensitive in immunocompromised pts with disseminated disease. May be negative in acutely ill patients and in those who are immunosuppressed.