Frequency
The prevalence of MCAP is unknown. At least 150 affected individuals have been reported in the medical literature. Because the condition is often thought to be misdiagnosed or underdiagnosed, it may be more common than reported.
Causes
MCAP is caused by mutations in the PIK3CA gene, which provides instructions for making the p110 alpha (p110α) protein. This protein is one piece (subunit) of an enzyme called phosphatidylinositol 3-kinase (PI3K), which plays a role in chemical signaling within cells. PI3K signaling is important for many cell activities, including cell growth and division (proliferation), movement (migration) of cells, and cell survival. These functions make PI3K important for the development of tissues throughout the body, including the brain and blood vessels.
PIK3CA gene mutations involved in MCAP alter the p110α protein. The altered subunit makes PI3K abnormally active, which allows cells to grow and divide continuously. Increased cell proliferation leads to the overgrowth of the brain, blood vessels, and other organs and tissues characteristic of MCAP.
MCAP is one of several overgrowth syndromes, including Klippel-Trenaunay syndrome, that are caused by mutations in the PIK3CA gene. Together, these conditions are known as the PIK3CA-related overgrowth spectrum (PROS).
Inheritance
MCAP is not inherited from a parent and does not run in families. In people with MCAP, a PIK3CA gene mutation arises randomly in one cell during the early stages of development before birth. As cells continue to divide, some cells will have the mutation and other cells will not. This mixture of cells with and without a genetic mutation is known as mosaicism.
Other Names for This Condition
- M-CM
- Macrocephaly cutis marmorata telangiectatica congenita
- Macrocephaly-capillary malformation syndrome
- MCAP
- MCMTC
- Megalencephaly cutis marmorata telangiectatica congenita
- Megalencephaly-capillary malformation-polymicrogyria syndrome
Additional Information & Resources
Genetic Testing Information
Genetic and Rare Diseases Information Center
Patient Support and Advocacy Resources
Clinical Trials
Catalog of Genes and Diseases from OMIM
Scientific Articles on PubMed
References
- Luks VL, Kamitaki N, Vivero MP, Uller W, Rab R, Bovee JV, Rialon KL, Guevara CJ, Alomari AI, Greene AK, Fishman SJ, Kozakewich HP, Maclellan RA, Mulliken JB, Rahbar R, Spencer SA, Trenor CC 3rd, Upton J, Zurakowski D, Perkins JA, Kirsh A, Bennett JT, Dobyns WB, Kurek KC, Warman ML, McCarroll SA, Murillo R. Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA. J Pediatr. 2015 Apr;166(4):1048-54.e1-5. doi: 10.1016/j.jpeds.2014.12.069. Epub 2015 Feb 11. Citation on PubMed or Free article on PubMed Central
- Martinez-Glez V, Romanelli V, Mori MA, Gracia R, Segovia M, Gonzalez-Meneses A, Lopez-Gutierrez JC, Gean E, Martorell L, Lapunzina P. Macrocephaly-capillary malformation: Analysis of 13 patients and review of the diagnostic criteria. Am J Med Genet A. 2010 Dec;152A(12):3101-6. doi: 10.1002/ajmg.a.33514. Citation on PubMed
- Mirzaa GM, Conway RL, Gripp KW, Lerman-Sagie T, Siegel DH, deVries LS, Lev D, Kramer N, Hopkins E, Graham JM Jr, Dobyns WB. Megalencephaly-capillary malformation (MCAP) and megalencephaly-polydactyly-polymicrogyria-hydrocephalus (MPPH) syndromes: two closely related disorders of brain overgrowth and abnormal brain and body morphogenesis. Am J Med Genet A. 2012 Feb;158A(2):269-91. doi: 10.1002/ajmg.a.34402. Epub 2012 Jan 6. Citation on PubMed
- Mirzaa GM, Riviere JB, Dobyns WB. Megalencephaly syndromes and activating mutations in the PI3K-AKT pathway: MPPH and MCAP. Am J Med Genet C Semin Med Genet. 2013 May;163C(2):122-30. doi: 10.1002/ajmg.c.31361. Epub 2013 Apr 16. Citation on PubMed
- Riviere JB, Mirzaa GM, O'Roak BJ, Beddaoui M, Alcantara D, Conway RL, St-Onge J, Schwartzentruber JA, Gripp KW, Nikkel SM, Worthylake T, Sullivan CT, Ward TR, Butler HE, Kramer NA, Albrecht B, Armour CM, Armstrong L, Caluseriu O, Cytrynbaum C, Drolet BA, Innes AM, Lauzon JL, Lin AE, Mancini GM, Meschino WS, Reggin JD, Saggar AK, Lerman-Sagie T, Uyanik G, Weksberg R, Zirn B, Beaulieu CL; Finding of Rare Disease Genes (FORGE) Canada Consortium; Majewski J, Bulman DE, O'Driscoll M, Shendure J, Graham JM Jr, Boycott KM, Dobyns WB. De novo germline and postzygotic mutations in AKT3, PIK3R2 and PIK3CA cause a spectrum of related megalencephaly syndromes. Nat Genet. 2012 Jun 24;44(8):934-40. doi: 10.1038/ng.2331. Citation on PubMed or Free article on PubMed Central
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