Review Question - QID 211029

This patient’s presentation of a recurrence of fever, productive cough with blood, and night sweats in an immunocompromised host is suggestive of secondary (reactivation) tuberculosis. Secondary tuberculosis histologically features caseating granulomas, which feature an area of central necrosis, surrounded by epithelioid cells, multinucleated giant cells, and lymphocytes.

Patients who experience a weakening of the immune system have a risk of reactivation of their latent tuberculosis infection. The infection may disseminate to the vertebral column to cause osteomyelitis (Pott’s disease), which may be the cause of this patient’s back pain. Infection with M. tuberculosis classically produces cavitary lesions in the lungs with a histological characteristic of caseating granulomas with central necrosis.

Incorrect Answers:
Answer 1: Cells with increased nuclear-to-cytoplasmic ratio are characteristic of dysplasia in a neoplastic progression of cells. Dysplasia is not characteristic of M. tuberculosis infection.

Answer 2: Cellular debris and macrophages followed by cystic spaces and cavitation are characteristic of liquefactive necrosis, which is seen in abscesses in bacterial infections as well as infarcts in the brain.

Answer 4: A macrophage filled with fungal microorganisms is characteristic of Histoplasma infection. While Histoplasma infection can also affect immunocompromised hosts and have a histology of caseous necrosis, this patient presents with signs and symptoms that are more consistent with M. tuberculosis infection.

Answer 5: Noncaseating granulomas on biopsy are characteristic of autoinflammatory diseases, including sarcoidosis and Crohn disease.

Bullet Summary:
Caseous necrosis is seen in tuberculosis and other systemic fungal infections.