What is MCAP syndrome? 

MCAP Syndrome, or Megaencephaly Capillary Malformation and Polymicrogyria Syndrome is a rare genetic syndrome that causes irregular growth in parts of the body and the brain. Specific effects and severity vary from person to person, but common characteristics are brain overgrowth, hypotonia (low muscle tone), and developmental delays. Many patients also have vascular birthmarks and body asymmetry.

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Genetic Cause

M-CM is caused by mutations in a gene called PIK3CA that increase the activity of the gene. In most cases, these mutations happen spontaneously after conception, so that the gene is changed in a percentage of the body's cells. There are currently no known cases of inheritance. M-CM is one of many conditions caused by changes in PIK3CA and is part of a group of conditions known as PIK3CA-related overgrowth spectrum or PROS.

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Many Names

This condition was first defined in 1997 as M-CMTC for macrocephaly-cutis marmorata telangiectatica congenita. In 2007, M-CM for macrocephaly-capillary malformation was proposed to more accurately describe the vascular involvement. A newer name, MCAP for megalencephaly-capillary malformation was proposed in a 2012 paper that is now widely used in genetics literature. These names, along with other variations, all refer to the same condition.

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Source: m-cm.net