Hereditary puzzles in albinism: heterogeneity or phenotypical variation?

Important new evidence is now available which is making clearer the genetic factors underlying inherited deficiency of pigmentation, both in its oculocutaneous form, and in that (apparently) limited to the eye. Among 32 individuals with oculo-cutaneous albinism, described by the author in 1978, were two families with apparent pheno-typical variation. To explain this, further studies by light- and electron-microscopy are reported here, together with metabolic tests, and the results of tests of the visually evoked cerebral responses. The idea of 'non-complementary allelism' is suggested as a possible explanation. Support for the thesis of genetic heterogeneity is given by the evidence of non-allelic albino-albino marriages, more of which have been reported since Trevor-Roper's classic instance, including another possible example from my previously reported pedigree in 1981.