Histoplasmosis

Introduction 

Histoplasmosis is caused by Histoplasma capsulatum, an unencapsulated, dimorphic fungus, which has affinity to grow in soil containing bird or bat droppings 

-it is seen in Africa, India, Far East, the Ohio River and Mississippi River valleys in America, Canada 

-Histoplasmosis is the most prevalent endemic mycosis in North America

-mode of infection is usually the inhalation of mold microconidia 

Symptoms & Signs 

-Most patients are asymptomatic 

-In symptomatic, it takes the following forms which can overlap 

Acute Pulmonary Histoplasmosis: Fever, cough, chest pain, myalgias, arthralgias, arthritis, rash – toxic erythema, erythema multiforme, or erythema nodosum, pericarditis, mediastinitis; Chest radiographs usually show diffuse interstitial pattern 
Chronic Pulmonary Histoplasmosis: Upper lobe infiltrates, pulmonary consolidation and cavitation, closely resembling tuberculosis

Acute Progressive Disseminated Histoplasmosis: Dissemination to organs such as the liver, spleen, bone marrow, and lymphoreticular system; progressive weight loss, fever,anemia, hepatosplenomegaly; diffuse micronodular pulmonary infiltrates; common in AIDS patients

Chronic Progressive Disseminated Histoplasmosis: Oral or pharyngeal ulceration, hepatosplenomegaly, adrenal insufficiency (Addison disease) 

Cutaneous histoplasmosis: Guttate psoriasis-like papules, pustules, chronic ulcers, plaques, panniculitis 

Diagnosis 

Fungal culture (gold standard): identification of small, oval shaped, intracellular yeast-like cells of Histoplasma within macrophages in sputum, blood, bone marrow or biopsy specimens 

Serology: detection of antibodies to histoplasmin or the yeast cells; 

Urine: Histoplasmosis antigen testing 

Skin test: Histoplasmin skin test

Treatment 

Amphotericin B, Itraconazole, Voriconazole, Posaconazole, isavuconazole 

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