Oculocutaneous albinism

A group of genetic conditions affecting pigmentation in the skin, hair, and eyes

Oculocutaneous albinism (OCA) is a group of rare genetic disorders characterized by a reduction or complete lack of melanin pigment in the skin, hair, and eyes. This condition affects individuals of all ethnic backgrounds and is associated with vision problems and increased risk of skin damage due to sun exposure.

Types

Oculocutaneous albinism is classified into several types based on the specific genetic mutations involved. The most common types include:

OCA1

OCA1 is caused by mutations in the TYR gene, which encodes the enzyme tyrosinase. This enzyme is crucial for the production of melanin. OCA1 is further divided into two subtypes:

• OCA1A: Characterized by a complete absence of tyrosinase activity, resulting in no melanin production. Individuals with OCA1A have white hair, very pale skin, and light-colored eyes.
• OCA1B: Involves reduced tyrosinase activity, allowing for some melanin production. Individuals may have light blonde hair and slightly more pigmentation in the skin and eyes compared to OCA1A.

OCA2

OCA2 is the most common form of albinism worldwide and is caused by mutations in the OCA2 gene. This gene is involved in the transport of tyrosine, a precursor to melanin, into the melanosomes. Individuals with OCA2 typically have light skin and hair, but more pigmentation than those with OCA1.

OCA3

OCA3 is caused by mutations in the TYRP1 gene, which encodes the enzyme tyrosinase-related protein 1. This type is more common in individuals of African descent and results in reddish-brown skin, hair, and eye color.

OCA4

OCA4 is caused by mutations in the SLC45A2 gene, which is involved in melanin production. This type is more prevalent in certain populations, such as those of East Asian descent, and results in a phenotype similar to OCA2.

Symptoms

The primary symptoms of oculocutaneous albinism include:

• Hypopigmentation: Reduced pigmentation in the skin, hair, and eyes.
• Vision problems: Including nystagmus (involuntary eye movements), strabismus (misalignment of the eyes), photophobia (sensitivity to light), and reduced visual acuity.
• Increased risk of skin damage: Due to lack of melanin, individuals are more susceptible to sunburn and skin cancer.

Diagnosis

Diagnosis of oculocutaneous albinism is based on clinical evaluation, family history, and genetic testing. Eye examinations can reveal characteristic changes in the retina and optic nerve. Genetic testing can confirm the specific type of OCA by identifying mutations in the associated genes.

Management

There is no cure for oculocutaneous albinism, but management focuses on protecting the skin and eyes from sun damage and addressing vision problems. This includes:

• Sun protection: Using sunscreen, wearing protective clothing, and avoiding excessive sun exposure.
• Vision aids: Prescription glasses, contact lenses, and low vision aids can help improve visual function.
• Regular eye exams: To monitor and manage vision problems.

Related pages

• Albinism
• Genetic disorder
• Melanin
• Photophobia