rapidly progressing disease of young children, characterized histologically by abnormal fibroblasts containing a large number of dark inclusions which fill the central part of the cytoplasm except for the juxtanuclear zone (I cells), and clinically by severe growth impairment, minimal hepatomegaly, extreme mental and motor retardation, and clear corneas; inherited as an autosomal recessive trait, it is caused by failure of lysosomal enzymes to be incorporated into lysosomes.