Fig. 2

Diagnostic flow chart for mucopolysaccharidoses (MPS). The diagnosis of the MPS can be performed starting with a screening of the urine followed by quantitative assay of urinary glycosaminoglycans (GAGs) and, if available, by qualitative evaluation of the GAGs accumulated that can steer the enzymatic assay. Once the enzymatic defect has been determined, the molecular analysis will serve to identify the causative genomic variant. Note that keratan sulphate (KS) does not form a reaction product with any of the routinely methods reported here; hence, quantitative GAG assessment in Morquio syndrome (MPS IV) requires other techniques or the two enzymatic assays. Differential laboratory diagnosis includes multiple sulphatase deficiency and mucolipidosis II and III, in which GAGs accumulate because of their primitive defect involving some of the enzymes of the GAG degradation pathway. HS heparan sulphate, DS dermatan sulphate