The frequency of lysosomal storage diseases in The Netherlands

We have calculated the relative frequency and the birth prevalence of lysos omal storage diseases (LSDs) in The Netherlands based on all 963 enzymatica lly confirmed cases diagnosed during the period 1970-1996. The combined bir th prevalence for all LSDs is 14 per 100,000 live births. Glycogenosis type II is the most frequent LSD with a birth prevalence of 2.0 per 100,000 liv e births, representing 17% of all diagnosed cases. Within the group of lipi doses, metachromatic leukodystrophy (MLD) is the most frequent LSD. MLD was diagnosed in 24% of lipidoses and the calculated birth prevalence was 1.42 per 100,000 for all types combined. Krabbe disease, diagnosed in 17% of ca ses, also belongs to the more frequent lipid storage diseases in The Nether lands with a birth prevalence of 1.35 per 100,000. The birth prevalence of Gaucher disease, commonly regarded as the most frequent lipid storage disea se is 1.16 per 100,000 for all types combined. The combined birth prevalenc e for all lipid storage diseases is 6.2 per 100,000 live births. Within the group of mucopolysaccharidoses (MPSs), MPS I has the highest calculated bi rth prevalence of 1.19 per 100,000 (25% of all cases of MPS diagnosed), whi ch is slightly more frequent than MPS IIIA with an estimated birth prevalen ce of 1.16 per 100,000. As a group, MPS III comprises 47% of all MPS cases diagnosed and the combined birth prevalence is 1.89 per 100,000 live births . The birth prevalence of MPS II is 0.67 per 100,000 (1.30 per 100,000 male live births). All other MPSs are rare. The combined birth prevalence for a ll MPSs is 4.5 per 100,000 live births. Mucolipidoses and oligosaccharidose s are very rare with birth prevalences between 0.04 and 0.20 for individual diseases. Only 49 cases were diagnosed between 1970 and 1996. Their combin ed birth prevalence is 1.0 per 100,000 live births.