Glycoproteinoses are a group of autosomal recessive lysosomal storage diseases caused by deficient activities of enzymes that play important roles in the degradation of glycoproteins such as N-linked or O-linked oligosaccharides. The lack of a single enzyme leads to the complete blockage of the catabolic chain and results in the accumulation of undegraded oligosaccharides in lysosomes. Glycoproteinoses share many clinical features such as mental retardation, coarse facies, and dysostosis multiplex. Cathepsin A-deficiency causes combined sialidase and beta-galactosidase deficiency (Sialidosis and Galactosialidosis) due to its function in stabilising these two hydrolases.
The diagnosis is confirmed by measuring enzyme activity in leukocytes or fibroblasts.
Some diseases are described as some phenotypes.
(Sialidosis) Type 1: the mild form with late-onset. Type 2: the severe form with infantile onset.
(Galactosialidosis) The early infantile type. The late infantile type. The juvenile/adult type.
(alpha-Mannosidosis) Type 1: a severe form with hepatomegaly and early death. Type2: a mild form with hearing loss and mental retardation.
(Fucosidosis) Type 1: a severe form. Type2: a mild form.
(Schindler/ Kanzaki) Type1 (Schindler disease): a severe form. Type2 (Kanzaki disease): an adult-onset disorder. Type3: an intermediate disorder with mild-to-moderate neurologic manifestations.
