Ultrastructure of the skin of human albinos

As part of a combined genetic, electrophysiological, clinical and biochemical study in albinism, the ultrastructure of the epidermis of 47 albinos was investigated. On account of the amount of pigmented granules in the keratinocytes, the presence of distinct maturational stages of melanosomes, the occurrence of abnormal melanosomes in the melanocytes and keratinocytes and the packing of melanosomes in the keratinocytes, three groups can be distinguished. (1) Non-pigmented: the keratinocytes of these patients contain only premelanosomes stage I and II and completely lack pigmented granules. (2) Variably pigmented: the keratinocytes of these patients contain stage IV melanosomes in variable number. Premelanosomes stage II and Iii can be present. (3) Pigmented and macromelanosomes: the epidermis of these patients is characterized by the occurrence of macromelanosomes. In addition, the keratinocytes contain aggregated and non-aggregated melanosomes.Comparison of the ultrastructural observations with the clinical diagnosis according to Witkop et al (1978) revealed that non-pigmented epidermis is present in patients in which the diagnosis of tyrosinase-negative oculocutaneous albinism, tyrosinase-positive oculocutaneous albinism and yellow mutant oculocutaneous albinism was made. In addition, the non-pigmented epidermis is present in albinos with the differential diagnosis of autosomal recessive ocular albinism and tyrosinase-positive oculocutaneous albinism.Because pigmented moles are present in both tyrosinase-negative oculocutaneous albino patients and tyrosinase-positive oculocutaneous albino patients, this criterion can not be used in discriminating between tyrosinase-negative oculocutaneous albinism and tyrosinase-positive oculocutaneous albinism.A better concordance was found between the phenotype of the patients and the skin ultrastructure than between the phenotype and the hair bulb test.