β-Galactosidosis in Patient with Intermediate GM1 and MBD Phenotype.

[gm1 gangliosidosis]

A 5 -year -old girl with clinical and biochemical phenotypes encompassing both GM 1 -gangliosidosis (GM 1 ) and Morquio B disease (MBD ) is described . Mild generalized skeletal dysplasia and keratan sulfaturia were consistent with a diagnosis of MBD , while developmental delay and GM 1 -specific oligosacchariduria were consistent with GM 1 gangliosidosis . No observable β-galactosidase activity was detected in leukocytes , and two mutations , p .R 201 H (c .602 G >A ) and p .G 311 R (c .931 G >A ), were identified by gene sequencing . The R 201 H substitution has been previously reported in patients with both GM 1 and MBD , and G 311 R is a novel mutation . Our patient represents a further example of the clinical heterogeneity that can result from mutations at the β-galactosidase locus .