Mucolipidosis type II (ML II) and mucolipidosis type III (ML III) are caused by a defect of the GlcNAc-1-phosphotransferase complex, which is composed of three subunits, alpha, beta und gamma. Mutations of the gene GNPTAB encoding the alpha/beta subunits result in Mucolipidosis II (ML II, also called I-cell disease) or the clinically milder condition mucolipidosis (ML III) alpha/beta. ML III gamma (or ML IIIC) arises from mutations of the gene GNPTG encoding the gamma-subunit. The GlcNAc-1-phosphotransferase complex is responsible for the formation of the mannose-6-phosphate recognition marker required for correct targeting of lysosomal hydrolases to the lysosomes. A defect of this complex leads to missorting of multiple lysosomal enzymes ending in the accumulation of different non-degraded macromolecultes in several tissues and organs. In ML II (I-cell disease) clinical signs are present already in newborns, these include dysmorphic features with striking gingival hypertrophy, developmental disturbance, skeletal abnormalities, hepatosplenomgaly and cardiomyopathy; the patients often die in early childhood. The mucolipidosis III (ML III alpha/beta and ML III gamma) are slowly progressive disorders that mainly affect the skeletal, joint and connective tissue, but spare the central nervous system. The life expectany is hardly reduced.
Etiology: Deficiency of N-acetylglucosaminyl-1-phosphotransferase
Gene: GNPTAB Gene
Mode of inheritance: Autosomal recessive
Gesellschaft für Mukopolysaccharidosen e.V.
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