Neuronal ceroid lipofuscinosis type 2 (CLN2) disease, formerly known as classical late-infantile neuronal ceroid lipofuscinosis or Jansky-Bielschowsky disease (OMIM#204500), is a neurodegenerative genetic disorder with an autosomal recessive inheritance.1, 2Children with CLN2 have a deficiency of tripeptidyl peptidase 1 (TPP1), a soluble lysosomal enzyme, due to biallelic mutation in theTPP1gene, leading to abnormal deposition of lipopigments within the lysosomes and cell death, especially in neurons and in the retina.1, 2. The gene discussed is TPP1; the disease is late infantile neuronal ceroid lipofuscinosis.