Late infantile neuronal ceroid lipofuscinosis: a new mutation in Arabs

The neuronal ceroid lipofuscinoses are a group of dominant neurodegenerative, progressive, and fatal disorders characterized clinically by myoclonic epilepsy, in variable association with dementia, ataxia, and visual loss. Neuronal ceroid lipofuscinoses were classified into several phenotypes according to their age of onset: infantile, late infantile, juvenile, and adult. A specific phenotype was named "northern epilepsy," and its onset of signs occurs between ages 5-10 years. Deficiencies in the lysosomal activity of two specific enzymes were found in several types of neuronal ceroid lipofuscinosis: palmitoyl-protein thioesterase 1, encoded by the CLN1 gene, and tripeptidyl-peptidase 1, encoded by the CLN2 gene. Several mutations in CLN2 were described previously. We describe a novel mutation in two siblings of Israeli-Arab origin, with a clinical picture compatible with late infantile neuronal ceroid lipofuscinosis. Both siblings were found to be homozygous for a deletion of a C nucleotide at position 775 in exon 7 of the CLN2 gene. These findings have implications for the worldwide epidemiology of neuronal ceroid lipofuscinosis.