Friedreich's ataxia with nephrotic syndrome and convulsive disorder: clinical and neurophysiological studies with renal and nerve biopsies and an autopsy.

In a sibship of four, Friedreich's ataxia and minimal lesion nephrotic syndrome occurred in two siblings, a third sibling had Friedreich's ataxia, but no evidence of nephrotic syndrome; the fourth sibling had neither condition. The chance of Freidreich's ataxia and minimal lesion nephrotic syndrome occurring in two siblings is small, and suggested a common immunological abnormality. High dose prednisone and antimetabolites given for the nephrotic syndrome did not appear to affect the course of Friedreich's ataxia. The two siblings with Friedrich's ataxia and nephrotic syndrome developed epilepsy at age 15 years. All three children with Friedreich's ataxia had abnormal electroencephalograms (EEGs). These epileptiform EEG abnormalities were probably inherited from the mother, who had spike wave epilepsy. The neurologic deficits of Friedreich's ataxia, in turn, may have allowed the EEG trait to be expressed as a seizure disorder. The progressive ataxia and epileptic, sometimes myoclonic, seizures in these patients and the dentate nucleus changes in the autopsied patient were consistent with the diagnosis of dyssynergia cerebellaris myoclonica. This suggested that the latter disorder may represent a coincidence of two genetic entities: Friedreich's ataxia and spike wave epilepsy.