Oculocutaneous albinism

Oculocutaneous albinism
Classification and external resources
Specialty
ICD-10	E70.3
ICD-9-CM	270.2
OMIM	203100 203200 203290 606574
Patient UK	Oculocutaneous albinism
MeSH	D016115
GeneReviews	Oculocutaneous Albinism Type 1 Oculocutaneous Albinism Type 2 Oculocutaneous Albinism Type 4

Oculocutaneous albinism is a form of albinism involving the eyes ("oculo-"), skin ("-cutaneous"), and according to some definitions, the hair as well. Overall, an estimated 1 in 20,000 people worldwide are born with oculocutaneous albinism. OCA is caused by mutations in several genes that control the synthesis of melanin within the melanocytes. Four types of oculocutaneous albinism have been described, all caused by a disruption of melanin synthesis and all autosomal recessive disorders.

Types

Name	OMIM	Gene	Description
OCA1	203100	TYR	OCA1 is caused by an alteration of the tyrosinase gene, and can occur in two variations. The first is OCA1a, and means that the organism cannot develop pigment at all. The hair is usually white (often translucent) and the skin very pale. Vision usually ranges from 20/200 to 20/400. The second is OCA1b, which has several subtypes itself. Some individuals with OCA1b can tan and also develop pigment in the hair. One subtype of OCA1b is called OCA1b TS (temperature sensitive), where the tyrosinase can only function below a certain temperature, which causes the body hair in cooler body regions to develop pigment (i.e. get darker). (An equivalent mutation produces the coat pattern in Siamese cats.) Another variant of OCA1b, called Albinism, yellow mutant type (OMIM: 606952) is more common among the Amish than in other populations, and results in blonde hair and the eventual development of skin pigmentation during infancy, though at birth is difficult to distinguish from other types. About 1 in 40,000 people have some form of OCA1.
OCA2	203200	OCA2	The most common type of albinism, is caused by mutation of the P gene. People with OCA2 generally have more pigment and better vision than those with OCA1, but cannot tan like some with OCA1b. A little pigment can develop in freckles or moles. People with OCA2 usually have fair skin but often not as pale as OCA1, and pale blonde to golden, strawberry blonde, or even brown hair, and most commonly blue eyes. Affected people of African descent usually have a different phenotype (appearance): yellow hair, pale skin, and blue, gray or hazel eyes. About 1 in 15,000 people have OCA2. The gene MC1R doesn't cause OCA2, but does affect its presentation.
OCA3	203290	TYRP1	Has only been partially researched and documented. It is caused by mutation of the tyrosinase-related protein-1 (Tyrp1) gene. Cases have been reported in Africa and New Guinea. Affected individuals typically have red hair, reddish-brown skin and blue or gray eyes. Variants may include rufous oculocutaneous albinism (ROCA or xanthism) (OMIM: 278400). The incidence rate of OCA3 is unknown.
OCA4	606574	SLC45A2	Is very rare outside of Japan, where OCA4 accounts for 24% of albinism cases. OCA4 can only be distinguished from OCA2 through genetic testing, and is caused by mutation of the membrane-associated transporter protein (MATP) gene. Several German patients were identified in 2004.

See also

• Piebaldism
• List of cutaneous conditions
• List of cutaneous conditions associated with increased risk of nonmelanoma skin cancer