Perianal tuberculosis presenting as a Fournier's gangrene.

is a rare form of extrapulmonary tuberculosis that affects the perianal region. Fournier's gangrene is an aggressive necrotizing fasciitis that primarily involves the perianal area and external genitalia. A previously healthy 38-year-old man presented with a left perianal abscess. His condition deteriorated, leading to septic shock and multiorgan dysfunction syndrome. A CT scan displayed extensive necrotizing fasciitis. Treatment included broad-spectrum antibiotics, numerous surgical perineal debridements, a transverse loop colostomy, and hyperbaric oxygen therapy. We believe the patient had pre-existing asymptomatic, non-diagnosed perianal tuberculosis, and a subsequent bacterial superinfection resulted in a perineal local abscess that progressed to severe Fournier's gangrene. The diagnosis of tuberculosis was confirmed through positive cultures and molecular identification in perineal biopsies. The patient experienced a complex clinical course with complications such as myocardial necrosis, acute respiratory distress syndrome, rhabdomyolysis with severe critical illness polyneuromyopathy and internal jugular thrombosis. Fournier's gangrene resulted in air dissection throughout the perineal fasciae, extending to the abdominal wall muscles resulting in an infected extraperitoneal spontaneous hematoma, probably caused by therapeutic anticoagulation. An extraperitoneal surgical drainage was performed. This case emphasizes the complexities in diagnosing and managing both perianal tuberculosis and Fournier's gangrene.