A fibro-adipose vascular anomaly (FAVA) is a rare vascular anomaly occurring when the body’s own tissue infiltrates a muscle, creating a tumor-like mass typically found in one or more limbs.  

 

We all have fatty tissue - called adipose tissue - in our bodies.  Adipose tissue serves the important function of storing fat.  And we all have muscles in our extremities – our arms, hands, legs, and feet.  Our muscles are made up of collections of muscle cells called muscle fibers, along with blood vessels, tendons, and nerves.  The current hypothesis among experts is that in a patient with a fibro- adipose vascular anomaly, there is a disproportionate increase in fat in one or more muscles, combined with fibrous scar tissue, which disorganizes the normal pattern of muscle fibers. 

 

Unlike cancer, the mass of fibroadipose tissue does not destroy the healthy muscle tissue surrounding it.  Rather, the fibroadipose tissue grows and infiltrates the muscle tissue, as well as often infiltrating the blood vessels, tendons, and nerves.  In fact, the fibroadipose tissue tends to take over the entire muscle, causing swelling.  While this theory is supported by little scientific investigation, it nonetheless constitutes the best current explanation of FAVA growth.  

 

It is currently believed that FAVA pain is caused by several factors.  The fibrous scarring causes muscle rigidity and prevents stretching. Since the muscle cannot stretch optimally, this results in pain during activity.  Additionally, the nerves that pass through the muscle are entrapped by the scar tissue, preventing them from sliding freely during activity and contributing to the pain.  Another factor is the abnormal bundle of FAVA tissue entangling and stretching the nerves passing through the muscle.  If a FAVA has a significant venous component, pain may also be caused by swelling and inflammation of the vein (phlebitis/phlebectasia).    

 

In FAVA patients, the fibroadipose mass grows more rapidly than the extremity where it is located.  The rate of growth varies among FAVA patients, and its pattern of growth is not yet fully understood.  Nonetheless, it is currently believed FAVA does not spread within the body beyond the affected muscle(s).  

 

The cause of FAVA is unknown.  However, it is believed that in at least some patients, it involves a mutation of the PIK3CA gene, which is a gene involved in - among other things - regulating cell growth, division, movement, survival, and metabolism.  The mutation causing FAVA is a somatic mutation, meaning that it cannot be passed down to your children.     

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​Fibro-adipose vascular anomaly (FAVA) is a relatively new term.  FAVA was first recognized as its own disorder in 2014.  Prior to that, patients with FAVA were incorrectly diagnosed with a variety of vascular malformations.  Even today, many FAVA patients are misdiagnosed with venous malformations, hemangiomas, arteriovenous malformations, lymphatic malformations, and other vascular anomalies.    

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Learn more about FAVA with this downloadable educational brochure.

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