Hennekam syndrome is an inherited disorder that is characterized by abnormalities of the lymphatic system, which is part of both the circulatory system and the immune system. The lymphatic system is a network of vessels that transport white blood cells (lymphocytes), nutrients, and proteins in a fluid called lymph. In people with Hennekam syndrome, the lymphatic vessels are often dilated (lymphangiectasia), which can slow down the flow of lymph and cause the vessels to leak. As a result, people with this condition experience puffiness or swelling that is caused by a buildup of fluid within certain tissues (lymphedema). The affected vessels may also break open (rupture).

Genetic changes that cause disease are called pathogenic variants. Pathogenic variants in the CCBE1, ADAMTS3, or FAT4 gene cause Hennekam syndrome.

Hennekam syndrome is rare, although the exact prevalence is not known. At least 100 cases of Hennekam syndrome have been reported worldwide.

Hennekam syndrome is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a pathogenic variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Published Date: March 20, 2026
Published By: National Institutes of Health