Identical twins with the Rhnull phenotype of the regulator type in a Finnish Lapp family.

An inbred family A. G. with identical twin sisters having the Rhnull phenotype of the regulator type as confirmed by the maternal family data of Rh inheritance is reported. The family was traced back through church records for six generations. Several connections could be established with a Norwegian Sea Lapp community in which a family with the amorph Rhnull type has been reported. The closeness of the Finnish and the Norwegian Lapps was given special attention since, despite both of the communities are small and share a more or less common gene pool, they nevertheless seem to possess the two ultra rare Rh genes, Xor in the Finnish and r in the Norwegian family, producing, when homozygous, the Rhnull phenotype.