Classical late‐infantile neuronal ceroid lipofuscinosis (CLN2; OMIM ID: 204500) is the result of tripeptidyl‐peptidase 1 (TPP1; EC 3.4.14.9) deficiency, caused by autosomal recessive inheritance of two pathogenic variants in trans in the TPP1 gene located on chromosome 11p15.4 (Gene ID: 1200).2, 3, 4. This evidence concerns the gene TPP1 and neuronal ceroid lipofuscinosis.