The nonsense mutation p.Tyr392∗, resided in exon 4, is the founder mutation in the Finnish population which resulted in a truncated protein lacking the C-terminal 16 amino acids and accounted for 83% of NCL cases caused by CLN5 defects in Finland (Savukoski et al., 1998). The gene discussed is CLN5; the disease is neuronal ceroid lipofuscinosis.