Histology of fetal eyes with oculocutaneous albinism.
The diagnosis of tyrosinase-negative oculocutaneous albinism (OCA) was made in a 19-week-old fetus by skin biopsy. Because the parents had an 11-year-old son with tyrosinase-negative OCA, they requested that the fetus be aborted at the 20th week of gestation. A histological analysis of the eyes was performed. Throughout the retina, the ganglion cell layer was separated from the inner neuroblastic layer by the inner plexiform layer. However, the number of ganglion cells was decreased and the nerve fiber layer was immature. Bipolar and horizontal cells had begun to segregate into the inner nuclear layer. Rods and cones were identifiable in the posterior, but not peripheral, retina. Cones were more numerous in the center of the retina, and no rod-free area was identifiable. In addition, the ciliary body (epithelial folds, blood vessels in the mesodermal connective tissue core, and ciliary muscle) was less developed than in a normal fetus. Melanosomes in the retinal pigment epithelium only contained filaments without melanization and were therefore classified as stage I or II melanosomes. However, the ciliary epithelium also contained some stage III melanosomes with melanin adherent to the filaments.