Morquio-like syndrome (MPS IV B) associated with deficiency of a β-galactosidase

Classic Morquio syndrome (MPS IV A) is an autosomal recessive disorder characterized by short stature, mild corneal clouding, thin enamel, normal intelligence and typical skeletal changes including platyspondylia and odontoid hypoplasia. Excessive keratan sulfate is excreted in the urine. The disorder results from a deficiency of galactosamine-6-sulfate sulfatase. Arbisser et al. described a girl with a mild Morquio-like syndrome, normal galactosamine-6-sulfate sulfatase activity, and β-galactosidase deficiency. They suggested that the condition be termed Morquio syndrome, type B (MPS IV B) to distinguish it from the classic Morquio syndrome, type A. We report a brother and sister who have many of the features of the Morquio syndrome (short stature, corneal clouding, thoracic kyphosis, pectus carinatum, mild dysostosis multiplex with platyspondylia and odontoid hypoplasia, and normal intelligence), but who are only mildly affected and have deficiency of a β-galactosidase against certain non-ganglioside substrates. In contrast to MPS IV A, their enamel is normal.