Tuberous sclerosis

Definition

Tuberous sclerosis is a group of two genetic disorders characterized by problems with the skin, brain/nervous system, and kidneys. There is also a predisposition to tumors. The diseases are named after a characteristic abnormal growth in the brain, which takes the shape of a tuber or root.

Alternative Names

Causes

Tuberous sclerosis is inherited as an autosomal dominant trait (only one parent must pass on the bad gene for the child to get the disease). However, a high percentage of cases are due to new mutations (which occur in the sperm or egg of one of the parents), so there usually is no family history of the disease.

It is one of a group of diseases described as neuro-cutaneous syndromes, because of large involvement of both the skin and the central nervous system (brain and/or spinal cord).

The symptoms of tuberous sclerosis vary considerably: from minimally affected people with normal intelligence and no seizures, to severely affected people with profound retardation and frequent, difficult-to-control seizures or serious tumors. Mutations in two genes, TSC1 and TSC2, are responsible for tuberous sclerosis.

Severely affected people may develop seizures shortly after birth. These are characterized by spasms (hypsarrhythmia). Mental retardation becomes evident as infants begin to miss their normal developmental milestones.

Infants may have heart tumors (rhabdomyoma), which can be detected by ultrasound. These tumors may grow or shrink and usually do not cause problems.

Several different skin lesions are common in tuberous sclerosis.

• "Ash leaves" are white lesions lacking normal skin color that have the shape or appearance of an ash leaf and may appear anywhere on the body.
• Shagreen patches: These appear on the lower back as raised patches of skin with an orange-peel texture.
• Adenoma sebaceum (angiofibroma): These lesions include red, highly vascular (containing many blood vessels) lumps on the face that may resemble irritated acne. These enlarge with age and may run together (become confluent) to form larger patches.

There are no known risk factors other than having a parent with tuberous sclerosis. In that case, each child has a 50% chance of inheriting the disease.