Pulmonary Histoplasmosis in a patient with Cough, Dyspnea, Pulmonary Nodule and Rheumatologic Manifestations: Case Report and Review

Abstract

Histoplasmosis has worldwide distribution, occurring most commonly in North, Central, and South America, as well as parts of Africa and Asia [1, 2]. Histoplasmosis is a granulomatous disease caused by a dimorphic fungus Histoplasma capsulatum (H. capsulatum). There are two varieties of H. capsulatum that are pathogenic to humans, H. capsulatum var. capsulatum and H. capsulatum var. duboisii. H. capsulatum var. capsulatum is endemic in eastern United States and Latin America [3], and H. capsulatum var. duboisii is prevalent in Africa and South East Asia [4]. In the United States, H. capsulatum is primarily seen in Mississippi and Ohio River valleys. H. capsulatum grows best in soil contaminated with bird or bat droppings [5]. Transmission occurs via inhalation of H. capsulatum spores from the soil. Sites commonly associated with exposure to H. capsulatum include old buildings, caves, bridges, where birds have roosted [6, 7]. Infection may be acquired from exposure to outdoor activities such as exploring caves, construction, remodeling, demolition, bird handling, all of which can cause inhalation of the pathogen through the contaminated soil [8, 9]. The variation in clinical course due to histoplasmosis depends on the extent of the exposure to the organism. Histoplasmosis may remain asymptomatic in most healthy individuals following low-level exposure and asymptomatic pulmonary histoplasmosis is the most common syndrome following infection [10]. Fewer than five percent of exposed individuals develop symptomatic disease after a low level exposure to H. capsulatum [11]. Symptomatic infection usually causes self-limited pulmonary illnesses, rheumatologic manifestations such as arthritis or arthralgia involving the large or small joints, dermatologic manifestations such as erythema nodosum and/or erythema multiforme or pericarditis. Exposure to heavy inoculum can cause diffuse pulmonary involvement [12]. Individuals at the extremes of age or with underlying immunosuppressive conditions can develop progressive disseminated disease. Histoplasmosis can involve every organ system during the course of dissemination [13]. Here, we describe a case of pulmonary histoplasmosis in a healthy adult female presenting with cough, dyspnea, pulmonary nodule and rheumatologic manifestations.