Histoplasmosis

Abstract

Histoplasmosis is a fungal infection acquired by inhalation of Histoplasma capsulatum microconidia. Microconidia are inhaled and deposited in the terminal bronchioles and alveoli of the lung. Clinical manifestations of histoplasmosis depend on the size of the inoculum and the patient’s immunological status/underlying conditions. Low level of exposure in the healthy host typically leads to asymptomatic infection, while the acute syndrome usually follows heavy inoculums. Acute pulmonary histoplasmosis causes widespread inflammation of respiratory tract, presenting with acute rhinitis, pharyngitis, tonsillitis, laryngitis, and tracheobronchitis. Chronic pulmonary histoplasmosis manifests as lung parenchymal disease with cavitation and interstitial fibrosis. Acute disseminated histoplasmosis with multisystem involvement is seen in immunocompromised individuals. Chronic histoplasmosis is associated with ulcerative, fungating lesions and granulomas in the upper respiratory tract. It presents as nasal and oral granuloma formation with cartilage and bone destruction, granuloma of the larynx and rarely involves middle ear and mastoid. Definite diagnosis is reached by isolating the fungus in special cultures, while alternate methods include detection of yeast forms in diseased tissues or detecting serum antibodies or specific antigens. Treatment consists of intravenous amphotericin B for 1 week followed by oral itraconazole for 6–12 weeks along with surgical excision of the granulomatous mass.