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E1375. Clinical and Radiologic Manifestations of Histoplasmosis: A Review
Authors
  1. Weibo Fu; Augusta University Medical Center; Medical College of Georgia at Augusta University
  2. Max Mam; Augusta University Medical Center; Charlie Norwood VA Medical Center
  3. Jayanth Keshavamurthy; Charlie Norwood VA Medical Center
Background
Histoplasmosis is the most common systemic fungal infection in North America. It is caused by the soil fungus Histoplasma capsulatum and is endemic to the central United States, particularly the Missouri, Ohio, and Mississippi river valleys and in areas with high amounts of bird and bat guano. Risk factors for developing symptomatic infection include increasing age, immunosuppression, and chronic respiratory disease. Manifestations of histoplasmosis infection vary depending on the acuity of infection and the individual’s comorbidities: Acute pulmonary histoplasmosis is asymptomatic in approximately 90% of cases. If present, signs may include flu-like symptoms, dyspnea, cough, hemoptysis, or dysphagia. Chronic pulmonary histoplasmosis usually occurs in individuals with underlying respiratory disease such as COPD, and symptoms are related to a gradual loss of pulmonary function. Disseminated progressive histoplasmosis, the most severe manifestation, is seen in individuals with deficient cell-mediated immunity, including patients on chronic corticosteroids or those with a CD4 count of <150 and can be rapidly fatal if left untreated.

Educational Goals / Teaching Points
The goal of this presentation is to provide an informative review of the epidemiology of pulmonary histoplasmosis. Additionally, this presentation aims to highlight the key clinical and radiographic distinctions between acute, chronic, and disseminated pulmonary histoplasmosis.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Radiographic findings for individuals with histoplasmosis can be classified according to the severity of the infection. Individuals with acute histoplasmosis often have normal chest radiographs, but atypical findings may include airspace consolidation, adenopathy, or formation of a histoplasmoma, a well-defined nodule with central calcifications. Chronic pulmonary histoplasmosis, seen in individuals with underlying respiratory disease, presents with findings such as migratory bronchopneumonia, adenopathy, calcified granulomas, and upper lobe cavitation. Lastly, imaging findings for disseminated progressive histoplasmosis include diffuse and/or miliary consolidation, upper lobe cavitation, adenopathy, broncholithiasis, fibrosing mediastinitis, hepatosplenomegaly with multiple splenic calcifications, lytic bone lesions, and epididymitis and prostatitis.

Conclusion
Histoplasmosis is the most common systemic fungal infection in North America and is endemic to the central United States. Clinical and radiographic manifestations of histoplasmosis infection vary depending on the acuity of infection and comorbidities. It is thus useful to identify distinct radiologic findings of the various presentations of histoplasmosis to make a more accurate assessment of disease progression.