Morphologic basis of inherited coat-color dilutions of cats

The melanin granules in hair of black, smoke, blue, Chediak-Higashi-smoke, and pink-eyed dilution cats were studied. The hair of black cats contains numerous small dark brown to black melanin granules uniformly distributed throughout all portions. The basis for the dilution in smoke cats is a paucity of melanin granules in the basal portions of the hair. Blue cat hair has a larger basic melanin granule, some very large but relatively regularly shaped granules, and a non-uniform distribution of granules. The granules in the blue cat hair resemble those in the hair of dilute mice. The Chediak-Higashi trait causes even larger basic melanin granules than the blue dilution and enlarged and relatively irregularly shaped granules. The melanin granules in the hair of the pink-eyed dilution cat are very small, and are yellowish brown compared to the dark brown to black of those of black, smoke, and blue cats.