M-CM; M-CAP; Macrocephaly Capillary Malformation Syndrome; Megalencephaly Capillary Malformation Polymicrogyria Syndrome; Macrocephaly Cutis Marmorata Telangiectasia Congenital; MCMTC

Megalencephaly-Capillary Malformation Syndrome (M-CAP or M-CM) is a disorder characterized by overgrowth of several tissues in the body. Its primary features are a large brain (megalencephaly) and abnormalities of small blood vessels in the skin called capillaries (capillary malformations). Additional brain abnormalities can include excess fluid within the brain (hydrocephalus) and abnormalities in the brain's structure, such as Chiari malformation and polymicrogyria. Abnormal brain development can lead to abnormalities of somatic growth with body and brain asymmetry, seizures, low muscle tone, developmental delays, and distinctive facial features. Some affected individuals have fusion of the skin between two or more fingers or toes (cutaneous syndactyly). There is also an increased risk for congenital heart defects such as Tetralogy of Fallot. M-CAP is caused by mutations in the PIK3CA gene.

Diagnostic testing: Imaging studies documenting structural brain defects (such as megalencephaly, hemimegalencephaly, or polymicrogyria); and genetic studies documenting abnormal gene sequencing in the PIK3CA gene confirm the diagnosis.

Physical findings:

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  Macrocephaly;

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  Frontal bossing;

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  Dysmorphic face;

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  Hypotonia;

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  Cutaneous capillary malformations;

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  Focal or generalized somatic overgrowth, limb or digit asymmetry;

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  Digital anomalies (syndactyly, polydactyly);

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  Joint laxity; and

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  Abnormally soft, thick skin and underlying tissue (“doughy”).

ICD-9: 759.89

Prognosis depends on the severity of symptoms. Early death due to feeding difficulties, complex cardiac heart disease, or arrhythmia, has been reported in rare occasions. The gene involved in M-CAP is also associated with several types of cancer (in particular, a childhood form of kidney cancer known as Wilms tumor) and noncancerous tumors in the nervous system known as meningiomas.

Management of M-CAP requires a multidisciplinary approach (involving neurology, ophthalmology, cardiology, orthopedics, audiometry, physiotherapy, psychology and dermatology). Neurosurgery may be necessary for hydrocephalus or posterior fossa decompression.

SUGGESTED PROGRAMMATIC ASSESSMENT*

Suggested MER for Evaluation:

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  Clinical history and examination that describes the diagnostic features of the impairment;

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  MRI of brain; and

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  Genetic testing confirming mutations in the PIK3CA gene.

Suggested Listings for Evaluation:

REMARKS

Listing level severity must be documented.