Neuronal ceroid lipofuscinosis type CLN2: A new rationale for the construction of phenotypic subgroups based on a survey of 25 cases in South America

► CLN2 is the most frequent neuronal ceroid lipofuscinosis in South America. ► Two CLN2 groups have been recognized: I-null TPP1 activity; II-residual TPP1 activity. ► The variant juvenile phenotype comprises approximately 50% of CLN2 in South America. ► Slight residual TPP1 activity had an effect on the attenuation of the phenotype. ► The five most frequent South American mutations comprise 66% of pathological alleles.