albinism
Meaning of albinism: Pigment is only half the story, since the same genes shape the retina and the optic nerves, so eyesight is always involved.
Definition of albinism
Albinism is a group of inherited conditions in which the body makes little or no melanin, the pigment that colors skin, hair and eyes. The genes involved control individual steps in pigment production, so the result ranges from a complete absence of color to a reduction subtle enough to go unnoticed. Reduced vision is a consistent feature.
What forms does albinism take?
| Form | What it affects |
|---|---|
| Oculocutaneous albinism | Skin, hair and eyes together; several distinct genetic types are recognized, differing in which step of pigment production is disrupted and in how much color remains |
| Ocular albinism | Mainly the eyes, with skin and hair close to that of other family members |
| Syndromic forms | Reduced pigment alongside problems in other systems, such as a bleeding tendency in Hermansky-Pudlak syndrome or immune and neurological features in Chediak-Higashi syndrome |
Hair may be white, yellow, red or light brown, and skin ranges from very pale to only slightly lighter than expected for the family. Eye color is often blue or gray, and an iris holding almost no pigment can look pink or violet, because light passes through it and reflects back off the blood vessels of the retina rather than because the eye itself is red.
Why is vision always affected?
Melanin is not just a coloring agent. During development it guides the formation of the fovea, the small central pit of the retina responsible for sharp detail, and it guides the routing of nerve fibers from each eye to the correct side of the brain. Where pigment is missing, the fovea stays underdeveloped and a share of fibers cross to the wrong side, so the two eyes work together poorly. The usual consequences are reduced sharpness of vision that glasses only partly correct, involuntary eye movement called nystagmus, misalignment of the eyes, and marked sensitivity to bright light.
What does missing pigment mean for the skin?
Melanin absorbs ultraviolet radiation and limits how much reaches the dividing cells beneath. Without it, skin burns quickly and accumulates ultraviolet damage far faster, so rates of skin cancer are substantially raised and appear at younger ages. Because several different genes can produce a similar appearance, genetic testing is what identifies the specific type, which in turn indicates whether features outside the skin and eyes are expected.
Used in a sentence
The child was evaluated by ophthalmology for vision problems associated with albinism.
Good to know
Albinism encompasses several distinct genetic conditions rather than one single disorder, and the degree of pigment reduction and associated vision problems can vary considerably between the different types.
Word origin
Where “albinism” comes from
From Latin albus, meaning white, combined with the suffix -ism, indicating a condition.