Morquio B syndrome: A primary defect in β‐galactosidase

Abstract

Fibroblasts from patients with Morquio B syndrome contain normal numbers of beta-galactosidase molecules with normal turnover but strongly reduced activity per enzyme molecule. Various substrate affinities are abnormal: the Km for methylum belliferyl (MU)-beta-galactoside is 4-10-fold elevated and affinity for keratan sulphate and oligosaccharides, isolated from Morquio B urine, was not detectable. In contrast, these substrate affinities are normal for beta-galactosidase in adult type GM1-gangliosidosis fibroblasts. Cell hybridization studies demonstrate that Morquio B syndrome and infantile and adult type GM1-gangliosidosis belong to the same complementation group. From these results we conclude that Morquio B syndrome is caused by a mutation in the structural gene for beta-galactosidase, which is allelic to the mutations in infantile and adult type GM1-gangliosidosis. Urinary excretion of keratan sulphate and oligosaccharides is abnormal in Morquio B syndrome but normal in adult type GM1-gangliosidosis. The catalytic properties of beta-galactosidase in Morquio B syndrome and GM1-gangliosidosis provide a possible explanation for the distinct clinical manifestations in these disorders.

Occipital-cervical instability in Morquio disease: A presentation of two cases and a review of the literature

“…This rare, hereditary disorder, transmitted in an autosomal recessive pattern, is characterized by the reduction or absence of activity of N-acetylgalactosamine-6-sulfatase in Morquio type A, 14 or ␤-galactosidase in Morquio type B. 15 These enzyme deficiencies lead to a lack of degradation of keratan and chondroitin sulfate, which cause the clinical characteristics of skeletal dysplasia through intracellular accumulation.…”

Inestabilidad occipitocervical en la enfermedad de Morquio. Presentación de 2 casos y revisión de la literatura

“…Este raro trastorno hereditario, de herencia autosómica recesiva, se caracteriza por la ausencia o reducción de la actividad de la N-acetilgalactosamina-6-sulfatasa en Morquio tipo A 14 , o la enzima ␤-galactosidasa en Morquio tipo B 15 . Estas deficiencias enzimáticas conducen a una ausencia de degradación del queratán y condroitín sulfato, que causan las características clínicas de la displasia esquelética a través de la acumulación intracelular.…”

Maladie de Morquio : diagnostic à l’âge adulte

“…La dysmorphie de la face associe traits grossiers, prognathisme, bouche large, nez court antéversé avec racine aplatie, parfois macrocéphalie [10]. Les dents sont espacées ou mal positionnées avec un émail grisâtre et rugueux [12,13]. On retrouve souvent une insuffisance aortique tardive [10], plus rarement une hépatomégalie ou des hernies inguinales, une hypoacousie mixte [14], des opacités cornéennes se développant après dix ans, une dégénérescence rétinienne pigmentée ou un glaucome [10].…”