The unusual pattern of hereditary bleeding disorders in the province of Newfoundland and Labrador—Canada’s most Eastern Province

Abstract

Newfoundland and Labrador (NL), the most eastern province of Canada, is characterized by a unique topography and pattern of settlement. The current population is descended from a small founding population of indigenous Innu, Inuit and Mi’kmaq and an estimated 28,000 settlers. These settlers originated from Southwest England and Southeast Ireland and came to invest and work in one of the world’s richest fisheries. They settled in bays, coves and islands off the coast, in small settlements called out-ports. These isolated communities developed unusual patterns of genetic disease including an unusual prevalence of some extremely rare Hereditary Bleeding Disorders (HBD). This study was designed to document the prevalence of these rare disorders, at a snapshot in time, using our provincial HBD registry. These diagnoses were verified by reviewing the original initial diagnostic coagulation results to confirm or refute each diagnosis. When available, we also recorded the underlying mutation. Population based prevalence rates were then compared with data published from the World Federation of Hemophilia (WFH) Global Registry. The results are striking. Using the WFH data the per capita prevalence in NL of Hemophilia A, Factors V, XI, and XIII Deficiency are higher than that of mainland Canada minus Labrador by a factor of 2.89, 4.54, 5.44 and 9.22, respectively. The increased prevalence of mild Hemophilia A is explained by a founder effect of the Val 2016 Ala mutation. All the severe FXIII deficient patients are homozygotes for c.691-1 G > A mutation. These results show that NL’s unique geography and population distribution led to a genetic drift that increased the prevalence of some rare factor deficiencies. This comparatively high prevalence provides a potential pool of patients for genotype/phenotype research.