The causative molecular defect, a homozygous deleterious variant in the CTSD gene (NM_001909: c.268_269insC, p.(Gln90Profs*50)) leading to infantile neuronal ceroid lipofuscinosis (CLN 10, OMIM #610127, [10]) had already been identified previously before coming to our clinic through targeted NGS analysis of their first two children [9]. Here, CTSD is linked to infantile neuronal ceroid lipofuscinosis.