Histoplasmosis is a common endemic mycosis that is usually asymptomatic, but occasionally results in severe illness. Histoplasmosis and its causative agent, Histoplasma capsulatum, are found worldwide, but particularly in North and Central America. Within the United States, infection is most common in the midwestern states located in the Ohio and Mississippi River valleys. Among the endemic mycoses, it is the most common cause for hospitalization .
Disseminated histoplasmosis is a progressive extrapulmonary infection . Hematogenous dissemination probably occurs in most patients during the acute infection before cellular immunity develops. Disseminated disease occurs in approximately 1 in 2000 patients with acute infection. Most patients who develop disseminated histoplasmosis are immunosuppressed (eg, AIDS, solid organ transplantation, treatment with tumor necrosis factor-alpha inhibitors) or are at the extremes of age. In addition, chronic progressive disseminated histoplasmosis occurs rarely in older adults with no known immunosuppressing conditions. (See "Pathogenesis and clinical manifestations of disseminated histoplasmosis", section on 'Risk factors'.)
The diagnosis of disseminated histoplasmosis requires a high index of suspicion, recognition of the common modes of presentation, and familiarity with the appropriate diagnostic tests. Treatment is highly effective but relapse can occur in severely immunocompromised individuals.
The diagnosis and treatment of disseminated histoplasmosis will be reviewed here. The pathogenesis, risk factors for dissemination, and clinical manifestations of this infection and the diagnosis and treatment of localized pulmonary histoplasmosis are discussed separately. (See "Pathogenesis and clinical manifestations of disseminated histoplasmosis" and "Diagnosis and treatment of pulmonary histoplasmosis".)
The most common symptoms of disseminated histoplasmosis are fever, fatigue, and weight loss. Symptoms and signs may point to involvement of specific sites, such as the skin, oropharynx, gastrointestinal tract, central nervous system (CNS), and adrenal glands. (See "Pathogenesis and clinical manifestations of disseminated histoplasmosis".)