CLN2-disease is an NCL caused by biallelic loss-of-function variants in CLN2/TPP1 leading to reduced synthesis of tripeptidyl peptidase 1 (TPP1).1 After a period of either normal development or delayed speech, children present age 2–4 years with epileptic seizures and ataxia, progressing to loss of ambulation, dementia, blindness, and early death.2, -, 4 Cerliponase alfa (Brineura, BioMarin) is an enzyme replacement therapy (ERT) delivered by fortnightly intracerebroventricular infusion that prolongs life and slows progression in classical CLN2-disease.5 This evidence concerns the gene TPP1 and dementia.