Ocular melanin pigmentation anomalies in cats, cattle, mink, and mice with Chediak-Higashi syndrome: histologic observations.

The Chediak-Higashi syndrome (CHS) is a hereditary disorder of man, with the homologous condition reported in five animal species. Multiple defects, including oculocutaneous hypopigmentation, are present in individuals with this syndrome. Giant cytoplasmic granules, including melanosomes and lysosomes, are characteristic. In this study, eyes from CHS affected and control cats, cattle, mink, and mice were examined histologically to determine: 1) degree of pigmentation; 2) structure and distribution of melanin granules; and 3) morphology of cells and tissues containing melanin. The CHS cattle were found to be the most ocularly hypopigmented species, whereas CHS mouse eyes contained considerably more melanin than those of the other species. Melanin granules of abnormal sizes and shapes were present in neuroepithelial and uveal tissues of CHS animals of all four species. Depigmentation apparently had occurred in the CHS eyes, since less melanin was present in eyes of old CHS animals of each species than was present in eyes of young animals. In addition, melanin containing macrophages were common in CHS eyes, and the numbers of melanocytes and pigmented epithelial cells were decreased in older CHS eyes.