A large consanguinous family from Saudi Arabia with 4 affected children presenting with an autosomal recessive ataxia, generalized tonic-clonic epilepsy and mental retardation is reported from the Institut de Genetique, Universite Louis Pasteur, Illkirch, France; Division of Pediatric Neurology, King Saud University, Riyadh, Saudi Arabia; and other centers. None of the 4 had myoclonus or mental deterioration. MRI of one patient revealed posterior white matter hyperintensities and mild cerebellar vermis atrophy, and the muscle biopsy showed vacuolization of the sarcotubular system. EEG was normal in 2 patients and showed epileptiform discharges in 2, generalized in one and bioccipital in another. The defective gene was localized to a new disease locus on chromosome 16q21-q23. Epilepsy presented at age 9-12 months, and ataxia was noted when the children started to walk at 2-3 years. All 4 had psychomotor delay and learning disabilities. Deep tendon reflexes were diminished, plantar responses were equivocal, speech was dysarthric, and the eye exam showed nystagmus. 
COMMENT. The differential diagnosis of recessive spinocerebellar ataxia with progressive myoclonus epilepsy and/or generalized tonic-clonic seizures includes Unverricht-Lundborg disease, Lafora disease, neuronal ceroid lipofuscinoses, sialidoses, the sensory ataxia, neuropathy, dysarthria and ophthalmoparesis (SANDO) syndrome, and myoclonic epilepsy with ragged red fibers (MERRF) syndrome. Age at onset, absence of myoclonus and dementia, and EEG and MRI findings allowed exclusion of these disorders and the definition of a new cpilepsy/ataxia syndrome localized to the 16q21-q23 locus.