FAVA usually occurs in young adults with age group between 1 and 30 years.
More common in females with male to female ratio of 1:4.
Lower extremities are more commonly involved than upper extremities. Calf muscles are most commonly involved followed by the thigh.
PIK3CA gene mutation related overgrowth spectrum disorder.
Imaging features and differential diagnoses
MRI shows well-defined or infiltrative intramuscular masses which are hyperintense on T1, T2W due to presence of fatty component. On post gadolinium sequence, low flow heterogenous enhancement is seen mainly in late arterial or venous phases. Isolated muscle involvement or transfascial extension with or without subcutaneous involvement may be seen. Dilated tortuous veins are often seen within or adjacent the mass with either normal or dilated drainage veins. Reactive bone changes may be present.
DDs - Diagnosis is often delayed and missed as it has overlapping features with other conditions like venous malformation, intramuscular hemangioma, and soft tissue tumors.
Treatment - Oral sirolimus, embolization with or without surgery. Sclerotherapy is usually ineffective.
REFERENCES
Khera PS, Garg PK, Babu S, Elhence P, Tiwari S, Nk S. Fibro Adipose Vascular Anomaly: A Rare and Often Misdiagnosed Entity. Indian J Radiol Imaging. 2021 Nov 13;31(3):776-781. doi: 10.1055/s-0041-1736399.
Erickson J, McAuliffe W, Blennerhassett L, Halbert A. Fibroadipose vascular anomaly treated with sirolimus: successful outcome in two patients.Pediatr Dermatol.2017;34(06):e317-e320.