Albinism, Oculocutaneous, Type II Clinical CharacteristicsOcular Features: The iris and retina lack normal pigmentation and translucency of the iris can be demonstrated. Anomalous decussation of neuronal axons in the chiasm and foveal hypoplasia result in decreased visual acuity. Vision loss into the range of 20/100-20/200 does not progress after early childhood but is sometimes as good as 20/30. Nystagmus is often present from about 3-4 months of age although it is less severe than in type I oculocutaneous albinism (203100, 606952). The iris may darken to some extent with age. Strabismus has been reported. Significant refractive errors are often present and stereopsis is reduced. The VEP responses are altered and can be used to document abnormal chiasmal decussation. Systemic Features: Melanin pigment is reduced in the skin and hair as well as the eyes. Individuals at birth may be misdiagnosed as OCA type I but it is common for pigmentation to increase in older individuals resulting in yellow or reddish-blond hair and the appearance of freckles and nevi. The skin may be creamy-white but this is often not as striking as in OCAI. It is possible for tanning to take place in some patients. This condition in Africans or African Americans is sometimes called brown oculocutaneous albinism (BOCA). There is an increased risk of skin cancer of all types. GeneticsType II is the most common type of oculocutaneous albinism and is especially prevalent among individuals of African heritage and in several Native American populations. It is an autosomal recessive condition caused by homozygous 2.7 kb deletions in the OCA2 gene (15q24.3-q12). Heterozygotes have normal pigmentation. Oculocutaneous albinism type I (203100, 606952) is a separate disorder with many similar features caused by mutations in the TYR gene. Other types of autosomal recessive albinism are OCA3 (203290 ), and OCA4 (606574). Pedigree: Autosomal recessiveTreatmentTreatment Options: No treatment is available for the hypopigmentation. Low vision aids can be helpful. Significant refractive errors should, of course, be corrected and dark lenses may be helpful during outdoor activities. The skin should be protected from excessive sun exposure. ReferencesArticle Title: Molecular basis of albinism: mutations and polymorphisms of pigmentation genes associated with albinism Oetting WS, King RA. Molecular basis of albinism: mutations and polymorphisms of pigmentation genes associated with albinism. Hum Mutat. 1999;13(2):99-115. Review. PubMed ID: 10094567 Vision in albinism Summers CG. Vision in albinism. Trans Am Ophthalmol Soc. 1996;94:1095-155. PubMed ID: 8981720 African origin of an intragenic deletion of the human P gene in tyrosinase positive oculocutaneous albinism Durham-Pierre D, Gardner JM, Nakatsu Y, King RA, Francke U, Ching A, Aquaron R, del Marmol V, Brilliant MH. African origin of an intragenic deletion of the human P gene in tyrosinase positive oculocutaneous albinism. Nat Genet. 1994 Jun;7(2):176-9. PubMed ID: 7920637 Oculocutaneous albinism Gronskov K, Ek J, Brondum-Nielsen K. Oculocutaneous albinism. Orphanet J Rare Dis. 2007 Nov 2;2:43. Review. PubMed ID: 17980020 Read more about Albinism, Oculocutaneous, Type II
Molecular basis of albinism: mutations and polymorphisms of pigmentation genes associated with albinism Oetting WS, King RA. Molecular basis of albinism: mutations and polymorphisms of pigmentation genes associated with albinism. Hum Mutat. 1999;13(2):99-115. Review. PubMed ID: 10094567
Vision in albinism Summers CG. Vision in albinism. Trans Am Ophthalmol Soc. 1996;94:1095-155. PubMed ID: 8981720
African origin of an intragenic deletion of the human P gene in tyrosinase positive oculocutaneous albinism Durham-Pierre D, Gardner JM, Nakatsu Y, King RA, Francke U, Ching A, Aquaron R, del Marmol V, Brilliant MH. African origin of an intragenic deletion of the human P gene in tyrosinase positive oculocutaneous albinism. Nat Genet. 1994 Jun;7(2):176-9. PubMed ID: 7920637
Oculocutaneous albinism Gronskov K, Ek J, Brondum-Nielsen K. Oculocutaneous albinism. Orphanet J Rare Dis. 2007 Nov 2;2:43. Review. PubMed ID: 17980020
