Chiasmal Decussation in Oculo-Cutaneous Albinism Type 8.

Purpose

Albinism is a genetic disorder characterized by a defect in melanin biosynthesis. Ophthalmological and dermatological impairments vary according to the patient genotype and are highly heterogenous. Recently, variants in the DCT gene were showed to be responsible for a new type of oculocutaneous albinism (OCA) named OCA8. We report the ophthalmological, electrophysiological, and dermatological characteristics of three patients with genetically confirmed OCA8.

Methods

This is a retrospective study of three patients with OCA8. Complete dermatological, ophthalmological, and orthoptic examinations were performed with clinical exploration and multimodal imaging. Visual evoked potentials (VEPs) were performed to characterize chiasmal decussation in two of the three patients.

Results

The dermatological phenotype was mild, whereas all three patients exhibited infantile nystagmus syndrome with reduced visual acuity, foveal hypoplasia (grade 3), macular hypopigmentation (graded from 2 to 1), and iris transillumination (grade 3). Patients who could undergo a VEP examination exhibited signs of strong chiasmal misrouting.

Conclusions

Recently, pathogenic variants in the DCT gene were proven to cause OCA. Whereas patients with OCA8 exhibit a milder dermatological phenotype than others, their vision was initially described as impaired. The present report confirms previous findings and suggests that chiasmal misrouting is present in OCA8. This, together with recent findings in the murine model, supports the hypothesis that DCT regulates levels of L-Dopa and downstream signaling in the developing retina. These results convey critical future therapeutic implications.