Disease gene mapping in isolated human populations: the example of Finland.

The recent surge of interest in isolated human populations can be attributed largely to the advances in molecular genetics that now appear to produce an endless array of new data. However, the organised study of inherited traits and disorders in isolated populations started several decades ago. For example, at the beginning of the second half of this century several enthusiastic investigators at the Department of Paediatrics, University of Helsinki began to document rare diseases in Finns that either had not been previously described or were very rare elsewhere. The 'flagship' disease was congenital nephrosis described by Hallman et all and established as an autosomal recessive disorder by Norio.2 These were the heydays of biochemical genetics. Rapidly, as many as a dozen rare disorders, many of which were 'metabolic', were found with a high frequency in Finns. A landmark paper by Norio et aP carrying the title Hereditary diseases in Finland; rare flora in rare soil was published in 1973; it described 10 'Finnish' disorders. Another landmark paper had appeared a year earlier describing extensive blood group and serum marker studies in conjunction with genealogical features of the Finnish population.4 Further studies by Nevanlinna and his group have characterised the Finnish gene pool and offered interpretations regarding the Finnish population history and structure.5 8 The following is a brief review of 'Finnish' disease genes and the lessons that have been gained so far from their molecular study.