Infantile neuronal ceroid lipofuscinosis (INCL) is a progressive encephalopathy characterized by psychomotor deterioration, early visual loss, and an evanishing EEG. Mutations in the CLN1 gene encoding palmitoyl-protein thioesterase (ppt) have been reported in all Finnish INCL patients and in several non-Finnish North European patients. No cases have been contributed from the Mediterranean area thus far. We identified a single adenine insertion at nucleotide position 169 (A169i) in the CLN1 gene in a family in which the proband suffered from an INCL-like syndrome. The novel mutation was homozygous in blood from the proband, heterozygous in his healthy parents, and not found in control alleles. The mutation leads to an early stop codon resulting in an abnormal and truncated ppt protein. Our observations provide the first molecular characterization of an Italian INCL patient and expand the list of the known defects in INCL.