Fibro-Adipose Vascular Anomaly (FAVA), distinct congenital disorder characterized by muscular fibrofatty changes, dilated veins (phlebectasia) causing pain and contracture.
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Signs and symptoms
The age at presentation of FAVA is variable; ranging from the time of birth to 28 years. In the cohort described by Alomari, et al. from the Vascular Anomalies Center at Boston Children’s Hospital, FAVA was located, in descending order, in the calf, forearm/wrist and thigh. The most common presentation is severe pain. Calf lesions, particularly those located in the posterior compartment, are commonly associated with restricted ankle dorsiflexion (equinus contracture).
Genetics
FAVA is caused by postzygotic somatic mutations in PIK3CA, a gene in the receptor tyrosine kinase phosphatidylinositol 3-kinase (PI3)-AKT growth-signaling pathway. The PIK3CA gene is located on the long (q) arm of chromosome 3.
Diagnosis
The constellation of clinical, radiologic, and histopathologic findings typically allow the diagnosis of FAVA. The most helpful imaging studies are ultrasonography (US) and magnetic resonance imaging (MRI). The major imaging features of FAVA include the presence of complex intramuscular solid lesion replacing normal muscle fibers with fibrofatty overgrowth and phlebectasia. The extrafascial part is composed of fatty overgrowth, phlebectasia, and occasional lymphatic malformation. The histopathologic findings in FAVA include dense fibrous tissue, fat, and lymphoplasmacytic aggregates within atrophied skeletal muscle. Adipose tissue within skeletal muscles are associated with large, irregular, and sometimes excessively muscularized venous channels and smaller, clustered channels. Organizing thrombi, lymphatic foci and enlarged nerves encircled by dense fibrous tissue are also frequently noted in FAVA.
Management
Due to limb contracture, early orthopedic consultation is necessary. Achilles tendon lengthening (heel-cord release) and physical therapy can be helpful for treating equinus contracture.
Unlike classical venous malformations, pain in FAVA is multifactorial and clinical response to slcerotherapy of the venous component can be less effective. While intralesional steroid injections and nerve block may offer temporary or partial pain relief, the source of pain is often the solid intramuscular lesion. Surgical resection and image-guided percutaneous cryoablation may offer an effective control of pain in FAVA lesions.