Which are the causes of Megalencephaly Capillary Malformation Polymicrogyria Syndrome (mcap)?

TL;DR: Megalencephaly Capillary Malformation Polymicrogyria Syndrome (MCAP) is caused by post-zygotic, somatic activating mutations in the PIK3CA gene, which occur after conception rather than being inherited from parents. These genetic alterations lead to overactive cell signaling, resulting in the characteristic brain overgrowth and vascular malformations associated with MCAP.

What causes Megalencephaly Capillary Malformation Polymicrogyria Syndrome?

The primary driver of Megalencephaly Capillary Malformation Polymicrogyria Syndrome (MCAP) is a mosaic mutation in the PIK3CA gene. Unlike hereditary conditions passed down through DNA in every cell, MCAP is caused by "somatic" mutations. This means the mutation happens randomly in a single cell during early embryonic development, and only the cells that descend from that original mutated cell carry the genetic change. Because of this mosaicism, the severity of MCAP can vary significantly between individuals based on when and where the mutation occurred during development.

Is MCAP a genetic or inherited condition?

Megalencephaly Capillary Malformation Polymicrogyria Syndrome is a genetic disorder, but it is not inherited. It is not caused by the parents' genes, nor is it triggered by environmental factors like diet or maternal health during pregnancy. Because the mutation occurs after fertilization, it is a sporadic event. Geneticists view the PIK3CA mutation as the biological "switch" that stays stuck in the "on" position, leading to the following effects:

• Overactive PI3K/AKT/mTOR signaling pathways, which regulate cell growth.


• Increased cell proliferation, leading to the brain overgrowth (megalencephaly) seen in MCAP patients.


• Development of capillary malformations, which are clusters of abnormally widened blood vessels.

What is the status of current research into MCAP?

Medical researchers are actively investigating why these specific PIK3CA mutations occur and how to dampen the overactive signaling pathways. While the cause of Megalencephaly Capillary Malformation Polymicrogyria Syndrome is now well-identified, researchers are focused on targeted therapies—such as PI3K inhibitors—that could potentially slow or manage the overgrowth characteristic of MCAP. Currently, 23 members of the DiseaseMaps.org community are sharing their experiences, helping researchers better understand the clinical spectrum of this rare condition.

Next steps

• Consult a clinical geneticist to confirm a diagnosis through specialized molecular testing.


• Connect with the 23 members of the DiseaseMaps.org community to share experiences and coping strategies.


• Discuss current clinical trials involving PI3K inhibitors with your specialist physician.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Megalencephaly-capillary malformation-polymicrogyria syndrome.


• OMIM (Online Mendelian Inheritance in Man): #603310 - PIK3CA-related overgrowth spectrum.


• Orphanet: Megalencephaly-capillary malformation-polymicrogyria syndrome.


• Journal of Medical Genetics: Research on PIK3CA-related overgrowth spectrum (PROS).