Actinomycetoma of the wrist: diagnostic insights from a pathology perspective (case report).

Actinomycetoma is a chronic, progressive subcutaneous infection caused by filamentous bacteria of the Actinomycetales order, characterized by tumefaction, sinuses, and grains. We report a rare case of actinomycetoma affecting the wrist of a 45-year-old male, which presented as a chronic, slowly enlarging swelling with multiple discharging sinuses. Initial clinical suspicion was broad, encompassing various chronic infections or soft tissue tumors. However, definitive diagnosis was established through meticulous histopathological examination of a biopsy specimen, revealing characteristic "sulphur grains" composed of a basophilic bacterial colony surrounded by Splendore-Hoeppli phenomenon, alongside a mixed inflammatory infiltrate. Culture subsequently confirmed Nocardia brasiliensis. This case underscores the crucial role of integrated histopathology and microbiology in distinguishing actinomycetoma from other chronic granulomatous conditions, particularly in atypical anatomical locations, ensuring timely and appropriate therapeutic intervention.