From a clinical point of view, the time-wise counterpart to the classical juvenile CLN3 disease (JNCL), i.e., the juvenile onset CLN1 type, starts between the ages of 5 and 10 years, and is characterized by a cognitive decline as the initial symptom, followed by motor decline and seizures (7–17 years), whereas vision loss occurs rather late, only after 10–14 years of age (50, 51). The gene discussed is PPT1; the disease is Mental deterioration.