Two Cape Coloured siblings with typical features of Hurler's syndrome, but without mucopolysacchariduria or mucopolysaccharide accumulation in tissues, are presented. The clinical features, in conjunction with raised beta-D-galactosidase and alpha-L-fucosidase levels in fibroblast cultures from one of the patients, suggest the diagnosis of a mucolipidosis. Theories relating to the intracellular deficiency and extracellular excess of lysosomal enzymes in these conditions are reviewed. Phenotypical and cell culture differences between 2 siblings who display the same overall clinical syndrome, illustrate the genetic pleiotropism inherent in this group of diseases.