Granulomatous

Granulomatous refers to a form of chronic inflammation in which granulomas form as organized collections of immune cells. A granuloma is typically a nodular aggregate of activated macrophages, called epithelioid cells, often surrounded by lymphocytes and sometimes containing multinucleated giant cells. Granulomatous inflammation arises in response to persistent irritants or infections that are difficult to eradicate.

Two main histologic patterns are recognized: caseating (necrotizing) granulomas, which show central necrosis and are classically associated with tuberculosis and certain fungal infections; and noncaseating granulomas, which lack central necrosis and are seen in conditions such as sarcoidosis and some fungal infections. The presence of Langhans-type giant cells is a characteristic feature in many granulomas, though their exact appearance can vary.

Causes of granulomatous inflammation are diverse. Infectious agents such as Mycobacterium tuberculosis, Mycobacterium leprae, Histoplasma, and Coccidioides species are common etiologies. Noninfectious diseases include sarcoidosis, Crohn’s disease, and hypersensitivity reactions. Foreign bodies (suture material, splinters) and certain occupational exposures (beryllium, silica) can also trigger granuloma formation.

Pathogenesis typically involves a Th1-driven immune response with interferon-gamma–activated macrophages trying to contain the offending agent. Granulomas can help wall off persistent pathogens or irritants but may also cause tissue damage, fibrosis, and organ dysfunction if extensive or poorly resolved.

Diagnosis relies on tissue biopsy and histopathologic examination, supported by special stains and cultures to identify infectious organisms. Management depends on the underlying cause and may range from antimicrobial therapy to anti-inflammatory or immunosuppressive treatment.