Spontaneous intermuscular hematoma in mixed connective tissue disease: a case report.

Spontaneous large intermuscular hematoma secondary to mixed connective tissue disease (MCTD) is extremely rare. We report a 57-year-old female with long-standing MCTD admitted for abdominal pain and fever (septic shock due to E. coli pyelonephritis). On hospital day 8, she developed a left thigh hematoma (10  ×  14 cm). CTA failed to identify the bleeding vessel, but transcatheter arterial embolization (TAE) stabilized the hematoma. Subsequent surgical debridement was performed for hematoma-induced tissue necrosis. This case highlights that MCTD-related vascular fragility, combined with sepsis and DIC, increases hematoma risk. Prompt TAE and surgical intervention are critical to prevent catastrophic outcomes.