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Progressive mental regression in siblings with Morquio disease Type B (mucopolysaccharidosis IV B)
Author(s) -
Giuguani R.,
Jackson M.,
Skinner S. J.,
Vimal C. M.,
Fensom A. H.,
Fahmy N.,
Sjövall A.,
Benson P. F.
Publication year - 1987
Publication title -
clinical genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 102
eISSN - 1399-0004
pISSN - 0009-9163
DOI - 10.1111/j.1399-0004.1987.tb03296.x
Subject(s) - neuraminidase , mutation , mucopolysaccharidosis , locus (genetics) , disease , medicine , biology , genetics , gene , virus
A brother and sister with clinical and radiological features of Morquio disease, but with atypical mental regression, are described. Leucocyte and fibroblast β‐galactosidase activity was deficient in the siblings, while N ‐acetylgalactosamine 6‐sulphate sulphatase and neuraminidase were normal. Study of the residual fibroblast β‐galactosidase activity towards 4‐methylumbelli‐feryl and p‐nitrophenyl β‐D‐galactosides indicated that the mutation resembles that in typical Morquio B disease (increased Km and similar pH maximum) rather than that in GM 1 ‐gangliosidosis. The patients have therefore been classified as having Morquio B disease with atypical mental regression rather than GM 1 ‐gangliosidosis variants with particularly severe bony abnormalities. The mutation was, however, distinct from that in Morquio B disease since residual activity towards the alternative artificial substrate 4‐methylumbelliferyl‐β‐D‐fucoside was increased. The patients represent further examples of the heterogeneity that can result from mutation at the β‐galactosidase locus.