Histoplasmosis

Latent asymptomatic pulmonary histoplasmosis

Low-intensity exposure to fungus in otherwise healthy people.
This is clinically silent and may be discovered only incidentally on biopsy or autopsy, when localised granulomas may be detected in the lungs.

Acute respiratory histoplasmosis (symptoms <4 weeks)

Low-intensity exposure to fungus in otherwise healthy people; usually causes mild symptoms
Patients present with flu-like symptoms (e.g., fever, headache, malaise, abdominal pain, weight loss, dry or non-productive cough, chest pain, fatigue, arthralgias).
Findings on examination are usually unremarkable. Chest auscultation may be normal; scattered crackles and bronchial breathing may be heard in some patients.
Fungal burden is low. Enzyme immunoassay will detect urine antigen in approximately 30% of patients. Sputum culture has a sensitivity of approximately 15%. Serology is positive in most cases.

Acute respiratory histoplasmosis (symptoms >4 weeks)

Exposure to high fungal inocula in otherwise healthy people.
Symptoms persisting for >4 weeks may indicate that the patient is developing progressive disseminated disease, which may be arrested by effective therapy.
In patients with more severe respiratory symptoms, distant breath sounds may be heard during auscultation over a lung cavity.
Fungal burden is high. Antigen testing and cultures are often positive. Serology may be negative initially but then positive 1 month later.

Chronic pulmonary histoplasmosis

This occurs in patients with underlying lung disease (e.g., emphysema).
Infiltration of the upper lobes of one or both lungs can occur with cavitation.
The most common manifestations are productive cough, weight loss, fevers, malaise, and possibly haemoptysis.
Serology is positive in most cases and complement fixation titres are often high.

Disseminated histoplasmosis

Occurs primarily in immunocompromised patients, especially in patients with HIV infection.
Impaired cellular immunity from primary immunodeficiency, or secondary to tumour necrosis factor-alpha antagonists or immunosuppressive therapy, increases the risk of progressive, disseminated, life-threatening histoplasmosis.[14][18]
Fever is the most common symptom; however, headache, anorexia, weight loss, and malaise are frequent complaints.
Extrapulmonary manifestations can be varied, including skin lesions, hepatosplenomegaly, abnormal liver enzymes, pancytopenia, gastrointestinal involvement, and a sepsis-like syndrome.[2] Central nervous system dissemination of the disease may present as a brain lesion or meningitis.
Serology is positive in most cases, and complement fixation titres are often high.

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