Epidemiology of lysosomal storage diseases in Sweden.

Aim: There are more than 50 inherited lysosomal storage diseases (LSDs), and this study examined the incidence of clinically diagnosed LSDs in Sweden.

Methods: The number of patients diagnosed during 1980-2009 was compiled from the registries of the two Swedish diagnostic laboratories that cover the whole country.

Results: We identified 433 patients during the 30-year period, with a total incidence of one in every 6100 births and identified fairly constant annual diagnoses during the last 20 years. Krabbe disease was the most common (one in 39 000) followed by Gaucher disease (one in 47 000), metachromatic leukodystrophy and Salla disease. Gaucher disease was more frequent in Sweden than other European countries, due to a founder effect of the mutation (p.L444P) in northern Sweden. Metachromatic leukodystrophy was one of the most common LSDs, in common with other countries. Salla disease, which is very rare elsewhere, was the fourth most common, stemming from a founder mutation in the Salla region of northern Finland brought to Sweden by immigration.

Conclusion: The collective incidence of LSDs in Sweden was essentially equal to other European countries, but with a somewhat different disease pattern. Our findings have implications for diagnostic algorithms and treatment strategies.