Tuberous Sclerosis Complex TSC

This autosomal dominant disorder is caused by the inac-tivation of one of two genes: TSC1 or TSC2. The TSC1 gene product—hamartin—is encoded by chromosome 9. The TSC2 gene product—tuberin—is encoded by chromosome 16. A significant number of sporadic cases are caused by mutations in the TSC2 gene.

The syndrome presents in early childhood, usually with seizures. Seizures, mental retardation, and sebaceous adenomas of the face are principal features. A retinal phakoma (glial nodule), when present, is usually asymptomatic.

The cerebral pathology consists of histogenetic malformations of the neurons and glial cells including (a) cortical tubers, (b) subependymal glial nodules, and (c)

glial heterotopia in the white matter. (See Chapter 13.) These malformative lesions are capable of tumorous proliferation. Giant-cell subependymal astrocytoma is characteristic.

Hamartomas of the kidneys and rhabdomyoma of the heart are typical visceral manifestations.

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