SummaryThe study of a I y e a r old patient with a mucopolysaccharidosis different from those already known has given the opportunity to describe the clinical, biochemical and enzymic characteristics of N-acetylglucosamine-6-sulfate sulfatase deficiency.The patient was delayed physically and mentally, was hyperactive, and had a short attention span. He had fair complexion and verv blond. but coarse and excessive hair. He had mild hepatosplknomegaly and dysostosis multiplex, including hypoplastic odontoid Drocess of the atlas. ovoid vertebral bodies, small femoral epiphyses; and modest enlaigement of the ribs. He had. a mild, bilateral conductive hearing loss. The urine gave a strongly positive spot test with Azur A paper. Quantitative measurement of urinary glycosaminoglycans demonstrated increased excretion and inadequate degradation of heparan sulfate and keratan sulfate. The microscopic examination of the stained peripheral leukocytes revealed metachromatic material which formed a ring on the inner aspect of the cellular membrane in 20% of the lymphocytes. The rate of degradation of 35S04-labeled intracellular glycosaminoglycans by cutaneous fibroblasts was delayed and inadequate.The measurements of several lysosomal enzymes whose deficiencies are responsible for the known mucopolysaccharidoses gave results within normal ranges. Galactose-6-sulfate (Gal&S), N-acetylgalactosamine-6-sulfate (GalNAc-6-S), and N-acetylglucosamine-6-sulfate (GlcNAc-6-S) were prepared with chlorosulfonic acid, according to the method of Suzuki and Strominger (38). After chromatographic purification, aliquots of the three 6-sulfated monosaccharides were reduced with sodium borotritide.