Fibro-adipose vascular anomaly of the left calf in a child: A rare case report and literature review

Fibro-adipose vascular anomaly (FAVA) is a rare intramuscular vascular anomaly characterized by fibrofatty infiltration of skeletal muscle associated with abnormal vascular channels. It typically presents in children and adolescents with pain, swelling, and functional limitation and is frequently misdiagnosed as venous malformation, hemangioma, or arteriovenous malformation. We report the case of a 5-year-old female presenting with a 1-month history of swelling in the left calf associated with pain on movement and tenderness. Ultrasonography demonstrated a heterogeneous intramuscular lesion in the gastrocnemius muscle with intrinsic vascularity and both arterial and venous flow components, initially suggestive of a low-flow arteriovenous malformation. Plain magnetic resonance imaging revealed an ill-defined hyperintense lesion on STIR sequences within the superficial intramuscular plane, isointense on T1-weighted images. The patient underwent complete surgical excision. Histopathological examination revealed dense fibrocollagenous tissue admixed with adipose tissue, abnormal muscularized vascular channels, enlarged nerves, and infiltration into skeletal muscle bundles, confirming the diagnosis of FAVA. The postoperative course was uneventful with complete symptom resolution at 2-week follow-up. This case highlights the diagnostic challenges associated with intramuscular vascular anomalies and the importance of histopathological correlation for definitive diagnosis. Surgery is the definitive line of management.