Protection from sunlight is imperative and patients should wear clothing and sunscreen on exposed skin to prevent burning and reduce the risk of skin cancer. Strabismus surgery can be performed for functional or cosmetic reasons. Dark glasses may be needed to relieve photophobia. Management and treatmentĪnnual ophthalmologic examination is necessary and corrective lenses or glasses are given to improve visual acuity. Genetic counseling should be offered to at-risk couples (both individuals are carriers of a disease-causing mutation) informing them of the 25% risk of having an affected child at each pregnancy. This disorder is inherited autosomal recessively. Prenatal testing is possible for at risk pregnancies by molecular genetic testing. Differential diagnosisÄifferential diagnoses include the other forms of OCA and X-linked ocular albinism (XLOA) as well as syndromes with albinism as a feature such as Hermansky-Pudlak syndromes 1-11, Chediak-Higashi syndrome, Griscelli syndromes 1-3, and Waardenburg syndrome type II. Molecular genetic testing is usually necessary to make the correct diagnosis of this subtype. Alternating strabismus, reduced stereoscopic vision, and an altered visual evoked potential (VEP) are associated with the characteristic misrouting of the optic nerves at the chiasm. Ophthalmologic examination reveals visualization of the choroidal blood vessels, reduced retinal pigment and foveal hypoplasia. The characteristic clinical findings along with confirmatory genetic testing are used to diagnose OCA1A. Melanocytes contain no melanin, as without this enzyme the melanin biosynthetic pathway is blocked. The mutation leads to a completely inactive or incomplete tyrosinase enzyme polypeptide. OCA1A is caused by a mutation in the TYR gene (11q14.2) encoding tyrosinase. Patients have an increased risk of developing basal and squamous cell carcinomas but melanomas are rare. Patients do not tan, and if proper sun protection methods are not followed, skin becomes rough, coarse, thickened and can have solar keratoses. Nevi and ephelides are common but are unpigmented and pink. The reduction in visual acuity is associated with foveal hypoplasia. Visual acuity ranges from 20/100 and 20/400 and an alternating strabismus is often present. It continues throughout life but usually slows down after childhood and is less noticeable when a person is relaxed and well rested. Nystagmus may be present at birth or it may develop in the first 3 to 4 months of life. These features do not change throughout a patient's life. Irises are blue to pink and fully translucent. Patients have white skin and hair at birth. OCA type 1A (OCA1A) is considered to account for about half of the overall OCA1 cases among non-Hispanic, Caucasian patients. The worldwide prevalence of OCA1 is estimated at 1/40,000.
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