The neuronal ceroid lipofuscinoses are the most common autosomal recessive neurodegenerative disorders in children, with a worldwide incidence of 1 in 100 000 live births. Multiple clinical variants are caused by more than 400 mutations in at least 14 different genes. These progressive genetic disorders primarily manifest in the central nervous system because of an extensive loss of neurons, specifically in the cerebral and cerebellar cortices. Patients with mutations in CLN1, which encodes palmitoyl-protein thioesterase 1 (PPT1), primarily manifest with infantile neuronal ceroid lipofuscinosis (Haltia-Santavuori disease). Affected children usually present between 1 and 2 years of age and typically die by 8 to 13 years of age. We describe a patient with infantile neuronal ceroid lipofuscinosis with a novel c.776_777insA mutation in CLN1. This insertion induces a frameshift and a premature stop codon late within the CLN1 messenger RNA (mRNA) transcript which is likely recognized by nonsense-mediated translation repression, decreasing PPT1 abundance.