Histoplasmosis is endemic to the Americas, Africa, eastern Asia, and Australia. It is rare in Europe. Histoplasmosis is a fungal infection transmitted by exposure to dust contaminated with bird, chicken, or bat droppings. 90% of infections are asymptomatic or cause mild flu-like symptoms.

500,000 (US); 10,000,000 (Global)
Fungi (Endemic-Dimorphic)
Histoplasma capsulatum infection;
7-21 days, usually <15 days; [PPID, p. 3166]
Flu-like syndrome; dry cough; pleuritic chest pain; 99% are asymptomatic after a light inoculum, and 10-50% are asymptomatic after a heavy inoculum. [ID, p. 2220] 90% of infections are asymptomatic or cause mild flu-like symptoms; [CDC Travel]
Not transmitted from person to person except by inoculation of infected tissue; [CCDM, p. 286]
Infection is common, but chronic disease is rare. The five forms of the disease are asymptomatic, acute respiratory, acute disseminated, chronic disseminated, and chronic pulmonary. Most cases of histoplasmosis are detected as incidental radiographic findings such as enlarged mediastinal or hilar lymph nodes and pulmonary nodules. A high-dose exposure can cause an acute respiratory disease within 2 weeks of exposure. Complications of acute infection include arthralgias, erythema multiforme, erythema nodosum, mediastinal adenitis, pericarditis, and uveitis. Frank arthritis and pleural effusions are "distinctly uncommon." Splenic and liver calcifications are signs of resolved histoplasmosis. In severe cases, acute infection can precipitate respiratory failure. Chronic pulmonary disease resembles pulmonary tuberculosis with cavitation; it is found in patients with pre-existing emphysema. Immunocompromised patients are susceptible to the disseminated forms of histoplasmosis with the following complications: mucosal and skin lesions; hepatosplenomegaly and generalized lymphadenopathy; adrenal insufficiency; endocarditis; and infections of the GI tract, CNS, and bone marrow. GI infections may cause an abdominal mass. Patients with hilar lymphadenopathy may be asymptomatic or have dysphagia, chest pain, cough, and dyspnea.

Laboratory evidence of dissemination includes anemia, leukopenia, thrombocytopenia, and elevated hepatic transaminases. In acute and subacute pulmonary histoplasmosis, testing for antigens in urine and bronchoalveolar lavage fluid (BALF) makes the diagnosis in about 75% of the cases. The usefulness of serology is limited because the results remain positive for years after initial infection. 10% of residents in endemic areas have low levels of antibodies. False negatives are common in HIV infected patients. BALF should also be cultured and stained (Diff-Quick, Giemsa, and GMS). Antigen detection is a rapid test for diagnosis and monitoring response to treatment, but cross-reactivity in patients with blastomycosis, penicilliosis, and paracoccidioidomycosis. [CCDM, p. 285; Merck Manual, p. 1573; ID, p. 2220-1; Cecil, p. 2040-2; Harrisons, p. 600-1; Guerrant, p. 573-575, 921;] 5-10% of histoplasmosis patients present with a septic-shock syndrome with DIC. [Cohen, p. 855] Histoplasmosis is one of the uncommon causes of nodular lymphangitis; [Am Fam Physician 2001;63:326-32]

Over 90% of histoplasmosis cases are subclinical. In an acute primary infection 7-21 days after exposure, the main findings are fever, headache, nonproductive cough, chest pain, rales, patchy infiltrates, and hilar adenopathy. About 6% of patients have acute pericarditis. Most cases of progressive disseminated histoplasmosis occur in immunosuppressed patients. Diarrhea, abdominal pain, and ulcers of GI tract are common; ulcers of the skin, mouth, and throat are also found. In disseminated disease in AIDS patients, skin findings include petechiae, ecchymoses, maculopapular rash, nodules, and pustules. [PPID, p. 3166-71] Findings in disseminated disease include meningitis, brain lesions, coagulopathy, rhabdomyolysis, mediastinitis, and loss of vision (unclear link to H. capsulatum infection). {Merck Manual, p. 1574]

African histoplasmosis is caused by H. capsulatum var. duboisii, which is a larger yeast form up to 15 microns in diameter. The organism is resistant to phagocytosis by macrophages. It causes osteolytic bone lesions and skin ulcers, nodules, and abscesses. [PPID, p. 3171]
Tissue stains; Culture; Serology most useful in chronic forms: 4-fold rise is diagnostic & single titre of >1:32 is suggestive; Antigen detection: In AIDS patients, sensitivity is 95% (urine) and 85% (serum); [ABX Guide]
Americas, Africa, eastern Asia, & Australia; Rare in Europe; After exposure to dust contaminated with bird, chicken, or bat droppings; [CCDM] Global; African histo: cases reported (only a few 100) in Uganda, Nigeria, Zaire & Senegal; [PPID, p. 3162, 3171]
  • >arthralgia
  • >fatigue, weakness
  • >fever
  • >myalgia
  • E dysphagia
  • E pharyngitis
  • E stomatitis
  • G abdominal mass
  • G abdominal pain
  • G blood in stool
  • G diarrhea
  • G hepatomegaly
  • G liver function test, abnormal
  • H anemia
  • H leukocytosis
  • H leukopenia
  • H lymphadenopathy
  • H splenomegaly
  • H thrombocytopenia
  • N headache
  • N seizure
  • N stiff neck
  • R chest pain
  • R cough
  • R dyspnea
  • R hemoptysis
  • R sputum production
  • R wheezing
  • S lymphadenitis, acute
  • S lymphangitis
  • S nodular lymphangitis
  • S papules or plaques
  • S petechiae and ecchymoses
  • S pustule
  • S rash (exanthem)
  • S skin blister or vesicles
  • S skin or subcutaneous nodule
  • S ulcer of skin
  • X cystic or cavitary lesions
  • X hilar lymphadenopathy
  • X lung infiltrates
  • X pleural effusions
  • *acute renal failure
  • *ARDS
  • *arthritis
  • *bleeding tendency
  • *brain abscess or lesion
  • *cranial neuropathy
  • *encephalitis
  • *endocarditis
  • *epididymo-orchitis
  • *erythema nodosum
  • *hepatitis
  • *mediastinitis
  • *meningitis
  • *myelitis
  • *myocarditis
  • *osteomyelitis
  • *pericarditis
  • *pneumonia
  • *pneumonitis
  • *rhabdomyolysis
  • *sepsis
  • *shock
  • *uveitis
  • *weight loss




Fecally Contaminated Soil, Animal Excreta, Soil or Dust (Ingesting or Inhaling)
Birds and Poultry
  • AIDS patients
  • Cancer patients
  • Plow or excavate soil in endemic area
  • Raise dust from bird roosts, chicken coops, or bat-inhabited caves endemic area
  • Travel to endemic area
  • Work in a medical or research lab
1. (US) 500,000 infections annually in US; [Gorbach, p. 210] Endemic areas in Western Hemisphere, Africa, and Asia; [Harrison ID, p. 996]
2. (Global) 20 X US cases/yr;