Phenotypic diversity associated with arylsulfatase B deficiency

The classical form of the Maroteaux-Lamy syndrome (MPS VI) is characterized by dwarfism, dysostosis multiplex, dermatan sulfaturia, corneal clouding, preservation of intellect, and death in the late teens. The presence of phenotypic diversity was suggested by the report of McKusick (1972) that there might be a mild form of this disorder. With the report by Stumpf et al. that there was a deficiency of arylsulfatase B in MPS VI patients, it became possible to utilize enzymatic data as well as clinical findings to study this disorder. The authors report the biochemical and clinical findings in 11 patients, from 6 families, having marked alterations in mucopolysaccharide metabolism associated with a deficiency of arylsulfatase B activity. Four of these patients have the classical severe form of the disorder, 3 of the patients (including the original patient of McKusick) have the mild form of the disorder, while the remaining patients have phenotypes distinctly different from either of the above subtypes. Study of cultured fibroblasts from these patients using radioactive sulfate incorporation, cross correction, measurement of arylsulfatase B by both colorimetric and electrophoretic techniques, degradation of dermatan sulfate and cell hybridization studies failed to yield any detectable difference. It is suggested that the clinical phenotype associated with the absence of arylsulfatase B is wider than had been previously believed and that this occurs as a result of multiple alleles at the structural locus for arylsulfatase B.