Giant pigment granules in the retinal pigment epithelium of a fetus with X-linked ocular albinism

The retinal pigment epithelium (RPE) of a 21-week-old fetus with X-linked ocular albinism (XOA) was studied. Electron microscopy revealed giant pigment granules (macromelanosomes) with a vesiculoglobular substructure located in the equatorial and posterior regions. The giant pigment granules were similar to those found in the skin in neurofibromatosis, nevus spilus. xeroderma pigmentosum, and other conditions. Anteriorly, compound granules and melanosomes of unusual appearance that could be precursors of the macromelanosomes were present. Normal ellipsoidal melanosomes were observed in all areas, but were more common anteriorly.