Light Fixation Seizure Syndrome

Rauch et al. (1999) reported 2 sisters with a syndrome of severe developmental delay, ataxia, impaired social interaction, seizure disorder with early onset but without epileptiform electroencephalographic changes, and a striking light-fixating behavior which was associated with retinal cone dystrophy. Additionally, they had minor anomalies including peripheral iris hypoplasia, bluish sclerae, mild anteversion of nostrils, micrognathia, ear anomalies, broad halluces and thumbs, hypoplastic toenails, short perineal body, Mongolian spots, mild hirsutism, hypoplastic ridges in the hypothenar area, and distal axial triradii. Growth and general health were normal in both, but one also had tetralogy of Fallot and vesicoureteral reflux. Because this condition appeared to be previously undescribed, Rauch et al. (1999) postulated that it represents a 'new' autosomal recessive disorder with light-fixating behavior and retinal cone dystrophy as leading features. The fundi in these 2 patients had a normal appearance, but abnormal cone function was detected on the basis of decreased flicker-following response, low normal response to a single bright flash, and decreased visual evoked responses bilaterally. X-linked female-restricted epilepsy with mental retardation (EFMR; 300088) was considered unlikely because in that disorder development is normal until age 4 to 18 months and developmental regression occurs thereafter, presumably secondary to the grand mal convulsive disorder. There was no evidence of regression in the patients of Rauch et al. (1999) and hyperreflexia seen in the sisters is absent in the EFMR syndrome. All patients with EFMR remained ambulatory. Furthermore, cone dystrophy or light-staring behavior had not been described in patients with EFMR.