The Eyes of the Albino Child
Albinism is the genetically acquired lack of the skin pigment, melanin. The brown melanin pigment in our skin is very important for protecting us from the damaging wavelengths of light found in natural sunlight. However, our eyes also require a certain amount of melanin in order to function normally.
We all have seen the cute, pink-eyed albino bunnies and white mice. Most people don't realize that these animals have poor vision and can suffer many significant health problems as a result of their lack of pigmentation. Unfortunately, so may humans.
There are over fifteen forms of albinism, some which involve only the eyes and others which are referred to as oculo-cutaneous, meaning the both the eyes and the skin have deficient pigmentation. Many forms are inherited in a recessive pattern. This means that each parent of an affected child must carry one abnormal gene for albinism. However, the parents are normal since only one of the pair of chromosomes carries the abnormal gene. There is a sex-linked form of albinism, in which the mother carries the gene and passes it on to the male offspring. In this situation, her sons would be true albinos, whereas her daughters would be carriers of the trait (this pattern of inheritance is also seen in red-green colorblindness).
The degree of gene expression can vary, meaning that the child may have mild pigmentary abnormalities or severe ones. Ocular involvement can also vary in albinism. The central retina, called the fovea, tends to be underdeveloped or hypoplastic. This usually limits the child's visual acuity. The pigmented iris is usually translucent and can be seen to transmit reflected light when viewed through the microscope. Only rarely is the iris truly pink. Albino children may have nystagmus, a jerky, trembling movement of the eyes. Additionally, these children tend to have problems with crossing in of the eyes, as they grow older. If skin pigmentation is involved, these children are at higher risk for skin cancers.
Interestingly, two types of oculo-cutaneous albinism can be life threatening; Chediak-Higashi albinism is associated with an abnormal immune system, making the child more susceptible to deadly infections. Hermansky-Pudlak Albinism can present with abnormal blood clotting abilities, producing a child prone to bleeding and hemorrhage. Thus, any child with albinism needs to be screened for these specific variants.
Fortunately, albinism is quite rare in the general population with approximately one in 17,000 individuals being affected. Many go through life undetected.
