Oculocutaneous albinism type 2

Alternate names

Other Names: OCA2; Oculocutaneous albinism tyrosinase positive; Albinism 2; Albinism, oculocutaneous, type 2; Albinoidism; Tyrosinase-positive oculocutaneous albinism

Definition

Oculocutaneous albinism type 2 is a genetic condition that affects the coloring (pigmentation) of the skin, hair, and eyes. Affected individuals typically have very fair skin and white or light-colored hair.

Cause

This condition is caused by mutations in the OCA2 gene. OCA2 is located in the region of chromosome 15q.

Inheritance

Autosomal recessive inheritance, a 25% chance

OCA2 is inherited in an autosomal recessive manner, which means both copies of a gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they do not show signs and symptoms of the condition.

Signs and symptoms

• Oculocutaneous albinism type 2 (OCA2) is characterized by hypopigmentation of the skin and hair and the characteristic ocular changes found in all types of albinism, including nystagmus; reduced iris pigment with iris translucency; reduced retinal pigment with visualization of the choroidal blood vessels on ophthalmoscopic examination; foveal hypoplasia associated with reduction in visual acuity; and misrouting of the optic nerve fiber radiations at the chiasm, associated with strabismus, reduced stereoscopic vision, and altered visual evoked potentials (VEP).

• Individuals with OCA2 are usually recognized within the first three to six months of life because of the ocular features of visual inattention, nystagmus, and strabismus. Vision is stable to slowly improving after early childhood until mid- to late teens, and no major change or loss of established visual acuity occurs related to the albinism.
• The amount of cutaneous pigmentation in OCA2 ranges from minimal to near-normal compared to others of the same ethnic and family backgrounds. Newborns with OCA2 almost always have lightly pigmented hair, brows, and lashes, with color ranging from light yellow to blond to brown. Hair color may darken with age but does not vary substantially from adolescence to adulthood.
• Brown OCA, initially identified in Africans and African Americans with light brown hair and skin, is part of the spectrum of OCA2.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Iris hypopigmentation(Light eye color)

30%-79% of people have these symptoms

• Abnormality of the optic nerve(Optic nerve issue)
• Albinism
• Freckling
• Nystagmus(Involuntary, rapid, rhythmic eye movements)
• Photophobia(Extreme sensitivity of the eyes to light)
• Strabismus(Cross-eyed)
• Visual impairment(Impaired vision)

5%-29% of people have these symptoms

• Basal cell carcinoma
• Melanoma
• Squamous cell carcinoma of the skin

Diagnosis

The diagnosis of oculocutaneous albinism type 2 (OCA2) is established by presence of the following:

• Hypopigmentation of the skin and hair
• Characteristic ocular changes found in all types of albinism, including the following findings detected on complete ophthalmologic examination:

1. Infantile nystagmus (usually noticed between ages three and 12 weeks of life
2. Reduced iris pigment with iris transillumination
3. Reduced retinal pigment with visualization of the choroidal blood vessels on ophthalmoscopic examination
4. Foveal hypoplasia associated with reduction in visual acuity

• Misrouting of the optic nerve fiber projections at the chiasm associated with strabismus (that may not develop until later in infancy), reduced stereoscopic vision, and altered visual evoked potentials (VEP).

To confirm a firm clinical diagnosis (with concordance between the dermatologic and ophthalmologic features), perform complete sequence analysis of OCA2.

Treatment

• Correction of refractive errors with spectacles or (when age-appropriate) contact lenses may improve visual acuity; strabismus surgery can be considered for either functional (improved peripheral fusion) or cosmetic reasons. [1].
• Hats with brims and dark glasses or transition lenses often reduce discomfort in bright light (photodysphoria).
• Protection from sun exposure with appropriate skin-covering clothing and sunscreens prevents burning, consequent skin damage, and the enhanced risk of skin cancer. Skin cancer, including a slightly enhanced risk for cutaneous melanoma, is treated as for the general population.

NIH genetic and rare disease info

• NIH info on Oculocutaneous albinism type 2

Oculocutaneous albinism type 2 is a rare disease.

Oculocutaneous albinism type 2 Resources
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