Neurocutaneous Syndrome

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What is the most common neurocutaneous syndrome? 

Neurofibromatosis (NF) type I has an incidence of 1/3000 to 4000 of the population. Inheritance is autosomal dominant and the spontaneous mutation rate (chromosome 17) is very high (30% to 50%).

Clinical characteristics include café-au-lait spots, neurofibromas, axillary/inguinal freckling, optic gliomas, megalencephaly, mental retardation, seizures, and characteristic bony lesions.

Which neurocutaneous syndrome is associated with infantile spasms and a hypsarrhythmia pattern on electroencephalogram? 

Tuberous sclerosis (TS), an autosomal dominant disorder with genetic heterogeneity (similar phenotype with mutation on either chromosome 9 or 16). Incidence is 1/10,000 with a high-spontaneous mutation rate.

Clinical features include mental retardation, seizures, adenoma sebaceum, ash-leaf spots, shagreen patches, café-au-lait spots, subungual and periungual fibromas (Koenen’s tumors), gingival fibromas, dental enamel pits, retinal tumors (mulberry tumor of the optic disc), cardiac rhabdomyomas, renal angiomyolipomas, and CNS cortical tubers and subependymal hamartomas that calcify.

Of the more common neurocutaneous syndromes, which has no clear pattern of inheritance? 

Sturge–Weber syndrome (encephalofacial angiomatosis), which is less common than NF or TS. Patients have a facial port-wine stain (nevus) that is usually unilateral involving the V segment of the trigeminal nerve.

The nevus may involve the ocular choroidal membrane, causing glaucoma. Arteriography reveals extensive arteriovenous malformation involving the ipsilateral cerebral hemispheric dura.

In addition to brain and skin involvement, which other neurocutaneous syndrome has an immune disorder and a high propensity for malignancy? 

Ataxia-telangiectasia is an autosomal recessive disorder with an incidence of 1/100,000. Affected individuals develop telangiectasias by 2 to 4 years of age on exposed areas of skin and conjunctiva.

Progressive cerebellar ataxia begins within the first few years of life. Patients have decreased or absent IgA and IgE and decreased IgG and IgG .

Defective cellular DNA repair leads to increased spontaneous and radiation-induced chromosomal aberrations, inducing various neoplasias. The disorder is caused by inactivation of the ataxia-telangiectasia-mutated protein kinase involved in detecting double-stranded DNA breaks and helping to coordinate repair.

Sources

  • Kandit RS: Tuberous sclerosis complex and neurofibromatosis type 1: the two most common neurocutaneous diseases. Neurol Clin 20:941-964, 2002.
  • Lavin M: Ataxia-telangiectasia: from a rare disorder to a paradigm for cell signaling and cancer. Nat Rev Mol Cell Biol 9(10):759-769, 2008.

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