Morphologic and chemical biopsy findings in mucolipidosis IV

Based on typical clinical and morphologic features, biopsy findings in an 18-year-old girl afflicted with mucolipidosis IV are reported. She had had corneal clouding since early childhood, psychomotor retardation resulting in severe mental impairment, and pigmentary retinopathy. Biopsies of skeletal muscle, rectum, skin, and lymphocytes revealed by light microscopy increased activity of acid phosphatase and by electron microscopy, membranous and vacuolar lysosomal residual bodies in numerous cells, including striated muscle fibers and lymphocytes. An unidentified lipid was encountered by means of thin-layer chromatography in the muscle biopsy. Thus, skeletal muscle, rectum, skin, and lymphocytes are equally suitable for in vivo morphologic diagnosis of mucolipidosis IV.