On the incidence of fits and mental retardation in tuberous sclerosis.

OBJECTIVES To establish the frequency of fits and mental retardation in an unbiased group of tuberous sclerosis patients. METHODS Known tuberous sclerosis families with more than one affected person were ascertained for a genetic linkage study. A number of members were born after genetic counselling had been given after identification of the proband. These subjects were then carefully examined clinically and in many cases with cranial computerised tomography, renal ultrasound, and skeletal survey but not echocardiography. They provide an unbiased group of tuberous sclerosis patients and allow affected patients with normal intellect to be diagnosed. PATIENTS Thirty-seven tuberous sclerosis families were ascertained and 26 patients born after the family proband were identified. RESULTS Sixteen of these 26 patients suffered fits (62%) and 10 patients were mentally retarded (38%). CONCLUSIONS A lower incidence of fits and mental retardation has been found in an unbiased sample of tuberous sclerosis patients. The lifetime risk for fits might be higher had we been able to follow the patients for longer. However, we believe these are more appropriate figures to use in genetic counselling for this disease.