p.Asn77Lys homozygous CLN6 mutation in two unrelated Japanese patients with Kufs disease, an adult onset neuronal ceroid lipofuscinosis

Background: The neuronal ceroid lipofuscinosis (NCL) are a group of autosomal recessive neurodegenerative disorders that are characterized by the accumulation of ceroid lipofuscins. The NCLs are categorized into four classes based on the age of onset. Kufs disease is a rare adult-onset NCL caused by mutations in the CLN6 gene, which is rarely observed in the Japanese population. Case: We previously reported a case study on a patient with Kufs disease, whose parents had a consanguineous marriage. Later, we observed another unrelated patient with Kufs. Here we present the case and mutational gene report in patients with Kufs disease. Conclusions: Gene analysis results of the first patient revealed a homozygous mutation c231C > G, p.Asn77Lys in exon 3 and a homozygous c.297 + 48 A > T mutation in intron 3 in the CLN6 gene. The Asn amino acid is perfectly conserved among species. In silico analysis showed that the mutation is predicted to be probably damaging. Moreover, the second patient with Kufs disease also had the same homozygous mutations. These data suggest that the missense mutation must be pathogenic. Furthermore, the patients had lived in the same district; therefore, they both potentially inherited the founder effect mutations.