Pulmonary histoplasmosis: how to recognize this infection?

Histoplasmosis, caused by histoplasma capsulatum, is one of the main fungal infections respiratory in endemic regions. The forms of presentation can vary from self-limited to respiratory failure and chronic forms, and the clinical picture can be indistinguishable from tuberculosis. Early recognition and diagnosis are essential to avoid an unfavorable evolution of the disease.

Histoplasmosis

The disease is endemic in regions of North America, Central and South, with areas of Asia and Africa also showing high prevalence. The fungus colonizes the soil mainly in areas where birds are raised or places inhabited by bats due to the ease of developing in soils contaminated with the feces of these animals. Risk factors for the disease include residents of risk areas, extremes of age, male sex and HIV positive, especially those with CD4 counts below 200. It is estimated that about 5-15% of AIDS deaths are caused by histoplasmosis.

Diagnosis

The disease can present itself in three different ways : acute, chronic or disseminated pulmonary histoplasmosis. The acute form of the disease is usually asymptomatic, with an incubation period between 7 and 21 days. When symptomatic, it is characterized by flu-like symptoms such as fever, headache, dry cough, myalgias and chest pain.

Chest radiography may show bilateral hilar lymph nodes, eventually calcified, and signs of pneumonitis. Chronic pulmonary histoplasmosis resembles cases of mycobacteriosis and can often be difficult to distinguish. Patients may experience dyspnea, productive cough, weight loss, night sweats, and fever. The characteristic changes on chest tomography include nodules and consolidations, masses and even cavitations. In addition, the disease can evolve with areas of pulmonary fibrosis secondary to inflammatory involvement.

Patients with the disseminated form may present with oral ulcers and skin rash associated with other manifestations of the disease. The predominant radiological alteration is the miliary-type reticulonodular infiltrate, which may be normal in up to 50% of cases. These forms are usually associated with a high exposure load and for a prolonged time.

The gold standard for diagnosis is culture and histopathology media, which can take weeks to identify the fungus. Serologies performed by against immunoelectrophoresis and immunodiffusion can also be used, but with a chance of cross-reaction with other fungi.

Treatment

The recommended treatment is with itraconazole at a dose of 200-400 mg/day that can be used for three months to two years. In severe forms of the disease, amphotericin B is the drug of first choice. Prophylaxis can be done by avoiding handling and cleaning areas with bird feces and closed places with a high incidence of histoplasmosis. Individuals with HIV

may benefit from itraconazole prophylaxis depending on CD4 levels. Brazil has a high incidence of the disease, with several underdiagnosed cases. Its recognition is essential to avoid an unfavorable evolution of the disease.