Albinism is a group of inherited genetic conditions resulting from the body’s inability to produce a sufficient amount of melanin. Melanin is the pigment responsible for the color of skin, hair, and eyes, and it also plays a part in the development of certain optical nerves. Since melanin helps protect the skin from ultraviolet radiation, people with albinism are more susceptible to sun damage.
Oculocutaneous Albinism
Oculocutaneous albinism (OCA) is the most prevalent category of albinism, impacting the pigmentation of the eyes, hair, and skin. There are several subtypes of OCA, each linked to specific genetic mutations that influence the amount of melanin the body produces. This variation results in a wide spectrum of physical traits. The inheritance pattern for all types of OCA is autosomal recessive, meaning a child must inherit a copy of the causative gene from both parents.
The first subtype, OCA1, is caused by mutations in the TYR gene, which produces the enzyme tyrosinase. This enzyme is a catalyst in the first step of melanin production. In OCA1A, there is a complete absence of tyrosinase activity, leading to no melanin production and resulting in white hair, very pale skin, and light-colored eyes. In the OCA1B subtype, some tyrosinase activity is present, causing hair and skin to darken slightly with age.
The most common form of albinism worldwide, particularly among people of African descent, is OCA2. This type results from mutations in the OCA2 gene, which produces a protein that may regulate the pH of melanosomes where melanin is stored. With some melanin production occurring, individuals with OCA2 can exhibit pigmentation from creamy white to light brown skin and hair that can be light yellow, blond, or light brown.
A rarer form, OCA3, is associated with mutations in the TYRP1 gene. This type is most often seen in individuals from southern Africa. The clinical presentation of OCA3 includes reddish-brown skin, ginger or reddish-colored hair, and hazel or brown eyes. Vision problems with OCA3 are often milder compared to other forms of OCA.
OCA4 is caused by mutations in the SLC45A2 gene, which provides instructions for a protein involved in tyrosinase function. It is found primarily in people of East Asian descent. The physical characteristics of OCA4 are very similar to those of OCA2, with individuals having creamy white skin and hair that can range from light yellow to brown.
Ocular Albinism
Ocular albinism (OA) is a less common form that primarily affects the eyes, while the hair and skin may appear normal or only slightly lighter than other family members. This condition is caused by a gene mutation on the X chromosome, so it is inherited in an X-linked pattern. Because males have one X and one Y chromosome, a single copy of the mutated gene will cause the condition.
Females, having two X chromosomes, would need the mutation on both to be affected, which is very rare. They are more often carriers who may show subtle signs of the condition, like changes in retinal pigmentation, but have normal vision. The defining characteristics of OA are vision-related, stemming from the abnormal development of the eyes due to the lack of melanin.
Albinism with Related Syndromes
In some instances, albinism is a feature of a broader medical syndrome that affects multiple organ systems. These rare conditions are distinct from OCA and OA. Two of the most recognized syndromes are Hermansky-Pudlak syndrome (HPS) and Chediak-Higashi syndrome (CHS).
Hermansky-Pudlak syndrome is a form of albinism characterized by a bleeding disorder due to a defect in blood platelets. This can lead to easy bruising, nosebleeds, and prolonged bleeding after injury or surgery. Some individuals with HPS may also develop pulmonary fibrosis, a serious lung disease, and inflammatory bowel conditions. HPS is most common in people of Puerto Rican descent.
Chediak-Higashi syndrome is another rare type of albinism associated with a defect in the immune system’s white blood cells. This leads to a high susceptibility to recurrent bacterial infections. Neurological issues can also be a feature of CHS. People with this syndrome may have silvery hair and skin that appears slightly gray.
Common Vision Impairments
Nearly all forms of albinism are associated with significant vision impairments because melanin is involved in developing the retina and optic nerve pathways. These vision problems are present from birth and are not correctable to 20/20 vision with glasses or contact lenses. They are often the most challenging aspect of the condition.
Common vision issues include:
- Nystagmus, which involves rapid, involuntary movements of the eyes back and forth.
- Strabismus, a misalignment of the eyes where they may turn inward or outward, sometimes called “crossed eyes,” which can affect depth perception.
- Photophobia, an extreme sensitivity to bright light and glare, which occurs because the iris has little pigment to block light from entering.
- Foveal hypoplasia, the underdevelopment of the fovea (the part of the retina for sharp central vision), which leads to reduced visual acuity.
Diagnosis and Management
The diagnosis of albinism begins with a physical examination of an individual’s skin, hair, and eye pigmentation. A thorough eye exam by an ophthalmologist is used to identify characteristic vision problems. While physical and visual exams can strongly suggest albinism, genetic testing is the only way to confirm the diagnosis and identify the specific type.
There is no cure for albinism, so management focuses on addressing symptoms related to vision and skin protection. Protecting the skin from the sun is necessary to prevent sunburn and reduce the risk of skin cancer. This involves consistent use of broad-spectrum sunscreen, wearing sun-protective clothing, hats, and seeking shade. Regular skin checks by a dermatologist are also recommended.
Vision care is another component of managing albinism. This can include prescription eyeglasses or bifocals to correct refractive errors like nearsightedness or farsightedness. For photophobia, tinted glasses or contact lenses can provide comfort. Low-vision aids, such as magnifiers and screen-reading software, can assist with daily tasks and learning.