Types of Albinism
Albinism refers to a group of rare inherited disorders that are present from birth. Albinism affects the amount of pigment found in the skin, hair, and eyes. People with albinism usually have little to no pigment in their eyes, skin, and hair, but the degree of pigment loss can be quite variable. There are four types of Albinism:
- Oculocutaneous albinism
- Type 1—complete absence of pigment. Skin, hair, and eyes lack all pigment from birth. Freckles or moles will not appear at any time during their lifetimes. This group is divided into several subtypes depending on associated characteristics.
- Type 2—decreased pigment, but may still have freckles and moles. This form of albinism is more common among persons of African descent. This form may be associated with such minimal pigment loss that it is evident only by comparison with other non-affected family members.
- Both Type 1 and Type 2 albinism are usually associated with visual problems includingnystagmus (abnormal jumping movements of the eyes) and decreased visual acuity, which is frequently not fully improved with glasses or contact lenses.
- Type 3—reddish brown skin, reddish hair and hazel or brown eyes, generally black South Africans.
- Type 4––similar to type 2, predominantly in Japanese persons.
- X-Linked albinism––vision problems without changes in skin or hair.
- Hermansky-Pudlak––in addition to albinism, persons also have lung, bowel, and bleeding problems.
- Chediak-Higashi––in addition to albinism, persons also have immune problems with defects in white blood cells.
Albinism occurs as a result of altered genes. In most cases these genes are inherited from parents. It may be autosomal recessive or X-linked.
Autosomal recessive inheritance accounts for the vast majority of cases. This means that both parents carry one copy of an abnormal gene but do not have symptoms or signs of albinism. Children become affected only if they inherit one affected gene from each parent. In this form of inheritance, each child has a one-in-four chance of inheriting the condition. The abnormal gene reduces (or completely eliminates) the body’s ability to make a pigment called melanin. There are several dozen different genetic subtypes of albinism. Individuals can have full or partial absence of this pigment which will affect the color of eyes, hair, and skin.
The chance of inheriting an X-linked altered gene will vary by the sex of the baby. Females have two X chromosomes while males have one X and one Y. If only one parent is affected the daughter will have one affected X chromosome and one normal X chromosome. The daughter will be a carrier but not have signs or symptoms herself. The son however only has on X chromosome. If the X chromosone that the son inherits is affected than the child will have albinism.