Mucopolysaccharidosis Type IV

The predominant clinical feature of Morquio disease is progessive skeletal deformity leading to cervical cord compression. Types A and B are due to deficiencies of different enzymes involved in the degradation of keratan and chondroitin 6-sulphates (type A) or of keratan sulphate and other galactose-containing molecules such as glycoprotein oligosaccharides (type B). Clinical differentiation of the two types is not possible. The earliest deformities to be noticed in Morquio disease are knock-knees, short neck and sternal protruberance (pectus carnatum). Other skeletal deformities include flat vertebrae, deformity and fragmentation of the femoral heads and severe hypoplasia or absence of the odontoid process. In addition to the skeletal deformities patients may have mild corneal clouding, hepatomegaly and aortic valve disease. Intelligence is usually normal in both types, but progressive mental regression has been reported in two siblings with type B. Rarely, type A has been reported to present as hydrops fetalis.

Enzyme Tests:
N-acetylgalactosamine 6-sulphatase is determined for the diagnosis of Morquio disease type A. b-galactosidase is deficient in Morquio disease type B.

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