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Tyrosinase-positive oculocutaneous albinism(OCA2)

MedGen UID:
82810
Concept ID:
C0268495
Disease or Syndrome
Synonyms: Albinism 2; ALBINISM II; Albinism, oculocutaneous, type II; Albinoidism; OCA2; Oculocutaneous Albinism Type 2
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Sources: HPO, OMIM, Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in homozygotes. In the context of medical genetics, autosomal recessive disorders manifest in homozygotes (with two copies of the mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
Autosomal recessive inheritance (HPO, OMIM, Orphanet)
SNOMED CT: OCA2 - Tyrosinase-positive oculocutaneous albinism (26336006); Tyrosinase-positive oculocutaneous albinism (26336006)
 
Genes (locations): MC1R (16q24.3); OCA2 (15q12-13.1)
OMIM®: 203200
Orphanet: ORPHA79432

Disease characteristics

Excerpted from the GeneReview: Oculocutaneous Albinism Type 2
Oculocutaneous albinism type 2 (OCA2) is characterized by hypopigmentation of the skin and hair and the characteristic ocular changes found in all types of albinism, including nystagmus; reduced iris pigment with iris translucency; reduced retinal pigment with visualization of the choroidal blood vessels on ophthalmoscopic examination; foveal hypoplasia associated with reduction in visual acuity; and misrouting of the optic nerve fiber radiations at the chiasm, associated with strabismus, reduced stereoscopic vision, and altered visual evoked potentials (VEP). Individuals with OCA2 are usually recognized within the first three to six months of life because of the ocular features of visual inattention, nystagmus, and strabismus. Vision is stable to slowly improving after early childhood until mid- to late teens, and no major change or loss of established visual acuity occurs related to the albinism. The amount of cutaneous pigmentation in OCA2 ranges from minimal to near-normal compared to others of the same ethnic and family backgrounds. Newborns with OCA2 almost always have lightly pigmented hair, brows, and lashes, with color ranging from light yellow to blond to brown. Hair color may darken with age but does not vary substantially from adolescence to adulthood. Brown OCA, initially identified in Africans and African Americans with light brown hair and skin, is part of the spectrum of OCA2.  [from GeneReviews]
Authors:
Richard Alan Lewis   view full author information

Additional descriptions

From OMIM
Tyrosinase-positive oculocutaneous albinism (OCA, type II) is an autosomal recessive disorder in which the biosynthesis of melanin pigment is reduced in skin, hair, and eyes. Although affected infants may appear at birth to have OCA type I, or complete absence of melanin pigment, most patients with OCA type II acquire small amounts of pigment with age. Individuals with OCA type II have the characteristic visual anomalies associated with albinism, including decreased acuity and nystagmus, which are usually less severe than in OCA type I (Lee et al., 1994; King et al., 2001). OCA type II has a highly variable phenotype. The hair of affected individuals may turn darker with age, and pigmented nevi or freckles may be seen. African and African American individuals may have yellow hair and blue-gray or hazel irides. One phenotypic variant, 'brown OCA,' has been described in African and African American populations and is characterized by light brown hair and skin color and gray to tan irides. The hair and irides may turn darker with time and the skin may tan with sun exposure; the ocular features of albinism are present in all variants (King et al., 2001). In addition, previous reports of so-called 'autosomal recessive ocular albinism,' (see, e.g., Witkop et al., 1978 and O'Donnell et al., 1978) with little or no obvious skin involvement, are now considered most likely to be part of the phenotypic spectrum of OCA1 or OCA2 (Lee et al., 1994; King et al., 2001).  http://www.omim.org/entry/203200
From GHR
Oculocutaneous albinism is a group of conditions that affect coloring (pigmentation) of the skin, hair, and eyes. Affected individuals typically have very fair skin and white or light-colored hair. Long-term sun exposure greatly increases the risk of skin damage and skin cancers, including an aggressive form of skin cancer called melanoma, in people with this condition. Oculocutaneous albinism also reduces pigmentation of the colored part of the eye (the iris) and the light-sensitive tissue at the back of the eye (the retina). People with this condition usually have vision problems such as reduced sharpness; rapid, involuntary eye movements (nystagmus); and increased sensitivity to light (photophobia).Researchers have identified multiple types of oculocutaneous albinism, which are distinguished by their specific skin, hair, and eye color changes and by their genetic cause. Oculocutaneous albinism type 1 is characterized by white hair, very pale skin, and light-colored irises. Type 2 is typically less severe than type 1; the skin is usually a creamy white color and hair may be light yellow, blond, or light brown. Type 3 includes a form of albinism called rufous oculocutaneous albinism, which usually affects dark-skinned people. Affected individuals have reddish-brown skin, ginger or red hair, and hazel or brown irises. Type 3 is often associated with milder vision abnormalities than the other forms of oculocutaneous albinism. Type 4 has signs and symptoms similar to those seen with type 2.Several additional types of this disorder have been proposed, each affecting one or a few families.  https://ghr.nlm.nih.gov/condition/oculocutaneous-albinism

Clinical features

Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
Strabismus
MedGen UID:
21337
Concept ID:
C0038379
Disease or Syndrome
Strabismus (also known as squint) is a condition in which the eyes are not properly aligned with each other.
Hypopigmentation of the fundus
MedGen UID:
101805
Concept ID:
C0151891
Pathologic Function
Decreased amount of pigmentation of the retina.
Red hair
MedGen UID:
66796
Concept ID:
C0239803
Finding
Achromasia
MedGen UID:
569448
Concept ID:
C0333913
Cell or Molecular Dysfunction
An abnormal reduction in the amount of pigmentation (reduced or absent) of skin, hair and eye (iris and retina).
Blue irides
MedGen UID:
108297
Concept ID:
C0578626
Finding
A markedly blue coloration of the iris.
Freckles in sun-exposed areas
MedGen UID:
348494
Concept ID:
C1859923
Finding
Foveal hypoplasia
MedGen UID:
393047
Concept ID:
C2673946
Finding
Underdevelopment of the fovea centralis.
Reduced visual acuity
MedGen UID:
461148
Concept ID:
C3149798
Finding
Visual impairment
MedGen UID:
777085
Concept ID:
C3665347
Finding
Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery.

Recent clinical studies

Etiology

Stevens G, van Beukering J, Jenkins T, Ramsay M
Am J Hum Genet 1995 Mar;56(3):586-91. PMID: 7887411Free PMC Article
Kedda MA, Stevens G, Manga P, Viljoen C, Jenkins T, Ramsay M
Am J Hum Genet 1994 Jun;54(6):1078-84. PMID: 8198130Free PMC Article
Durham-Pierre D, Gardner JM, Nakatsu Y, King RA, Francke U, Ching A, Aquaron R, del Marmol V, Brilliant MH
Nat Genet 1994 Jun;7(2):176-9. doi: 10.1038/ng0694-176. PMID: 7920637
Lee ST, Nicholls RD, Schnur RE, Guida LC, Lu-Kuo J, Spinner NB, Zackai EH, Spritz RA
Hum Mol Genet 1994 Nov;3(11):2047-51. PMID: 7874125
Jenkins T, Heim RA, Dunn DS, Zwane E, Colman MA, Ramsay M, Kromberg JG
Ophthalmic Paediatr Genet 1990 Dec;11(4):251-4. PMID: 1982896

Diagnosis

Grucela AL, Patel P, Goldstein E, Palmon R, Sachar DB, Steinhagen RM
Am J Gastroenterol 2006 Sep;101(9):2090-5. Epub 2006 Jul 18 doi: 10.1111/j.1572-0241.2006.00733.x. PMID: 16848805
Uçakhan OO, Atmaca L, Sayli BS, Sayar C, Firat E
Acta Ophthalmol Scand 1999 Apr;77(2):238-40. PMID: 10321549
Izquierdo NJ, Townsend W, Hussels IE
Trans Am Ophthalmol Soc 1995;93:191-200; discussion 200-2. PMID: 8719678Free PMC Article
Iwata F, Kaiser-Kupfer MI
Curr Opin Ophthalmol 1994 Dec;5(6):79-83. PMID: 10150832
van Dorp DB
Clin Genet 1987 Apr;31(4):228-42. PMID: 3109790

Therapy

Grucela AL, Patel P, Goldstein E, Palmon R, Sachar DB, Steinhagen RM
Am J Gastroenterol 2006 Sep;101(9):2090-5. Epub 2006 Jul 18 doi: 10.1111/j.1572-0241.2006.00733.x. PMID: 16848805
Bothwell JE
Int J Dermatol 1997 Nov;36(11):831-6. PMID: 9427075
Colman MA, Stevens G, Ramsay M, Kwon B, Jenkins T
Hum Genet 1993 Jan;90(5):556-60. PMID: 8428754
Ramsay M, Colman MA, Stevens G, Zwane E, Kromberg J, Farrall M, Jenkins T
Am J Hum Genet 1992 Oct;51(4):879-84. PMID: 1415228Free PMC Article

Prognosis

Grucela AL, Patel P, Goldstein E, Palmon R, Sachar DB, Steinhagen RM
Am J Gastroenterol 2006 Sep;101(9):2090-5. Epub 2006 Jul 18 doi: 10.1111/j.1572-0241.2006.00733.x. PMID: 16848805

Clinical prediction guides

Kedda MA, Stevens G, Manga P, Viljoen C, Jenkins T, Ramsay M
Am J Hum Genet 1994 Jun;54(6):1078-84. PMID: 8198130Free PMC Article
Colman MA, Stevens G, Ramsay M, Kwon B, Jenkins T
Hum Genet 1993 Jan;90(5):556-60. PMID: 8428754
Walpole IR, Mulcahy MT
J Med Genet 1991 Jul;28(7):482-4. PMID: 1910093Free PMC Article
Jenkins T, Heim RA, Dunn DS, Zwane E, Colman MA, Ramsay M, Kromberg JG
Ophthalmic Paediatr Genet 1990 Dec;11(4):251-4. PMID: 1982896
Heim RA, Dunn DS, Candy SE, Zwane E, Kromberg JG, Jenkins T
Hum Genet 1988 May;79(1):89. PMID: 3130302

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