Two monozygous twin girls, now 7 years old, with complete concordance of an almost total universal albinism were found in an « isolate » near Aosta in the Western Italian Alps. Their parents show normal pigmentation, and are first cousins, their common grandmothers having a brother who was the grandfather of another albinotic girl, aged 22. The parents of the latter were examined by the Dutch ophthalmogeneticist P. J. Waardenburg: while her father did not show definitely diaphane irides, her mother did. As a similar discrepancy in otherwise normal parents of albinos was stated in 2 more families (Hanhart 1952), the presence of diaphane or not diaphane irides cannot be regarded as sufficient symptom to distinguish two different biotypes of simple-recessive universal albinism. Heterogeny, though rather probable, of this character has not yet been proved in white man.
In Switzerland, and Italy as well, there are considerable local accumulations of universal albinism, so that calculations on the basis of a medium frequency do not hold. The percentage of 7.9 for first cousin marriages of normal parents of albinotic children and 8% for second cousins can hardly be taken as a proof for heterogeny of the gene concerned.
The observation of monozygous twins with concordant universal albinism is the first made in Europe, and the third published all over the world. It is unique on account of the near consanguinity of the normal parents of these twins. Its incidence in Northern Italy speaks in favour of a relatively frequent occurrence of this character in this country, suggested already by the author's population studies.