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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; Oculocutaneous albinism type 2
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Autosomal recessive inheritance refers to genetic conditions that occur only when mutations are present in both copies of a given gene (i.e., the person is homozygous for a mutation, or carries two different mutations of the same gene, a state referred to as compound heterozygosity).
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]
Full text of GeneReview (by section):
Summary  |  GeneReview Scope  |  Diagnosis  |  Clinical Characteristics  |  Differential Diagnosis  |  Management  |  Genetic Counseling  |  Resources  |  Molecular Genetics  |  References  |  Chapter Notes
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). The four types of oculocutaneous albinism are designated as type 1 (OCA1) through type 4 (OCA4). 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. Because their features overlap, the four types of oculocutaneous albinism are most accurately distinguished by their genetic cause.  http://ghr.nlm.nih.gov/condition/oculocutaneous-albinism

Clinical features

Melanoma
MedGen UID:
505377
Concept ID:
CN002586
Finding
The presence of a melanoma, a malignant cancer originating from pigment producing melanocytes. Melanoma can originate from the skin or the pigmented layers of the eye (the uvea).
Neoplasm of the skin
MedGen UID:
428780
Concept ID:
CN007095
Finding
A tumor (abnormal growth of tissue) of the skin.
Strabismus
MedGen UID:
21337
Concept ID:
C0038379
Disease or Syndrome
Strabismus is the intermittent or constant misalignment of an eye so that its line of vision is not pointed at the same object as the other eye. Strabismus is caused by an imbalance in the extraocular muscles which control the positioning of the eyes. Strabismus is normal in newborns but should resolve by the time the baby is 6 months old. In older children with strabismus, the brain may learn to ignore the input from one eye, and this may lead to amblyopia, a potentially permanent decrease in vision in that eye if not corrected.
Visual impairment
MedGen UID:
22663
Concept ID:
C0042798
Finding
Vision considered to be inferior to normal vision as represented by accepted standards of acuity, field of vision, or motility. Low vision generally refers to visual disorders that are caused by diseases that cannot be corrected by refraction (e.g., MACULAR DEGENERATION; RETINITIS PIGMENTOSA; DIABETIC RETINOPATHY, etc.).
Nystagmus
MedGen UID:
409575
Concept ID:
C1963184
Finding
Foveal hypoplasia
MedGen UID:
393047
Concept ID:
C2673946
Finding
Photophobia
MedGen UID:
504524
Concept ID:
CN000575
Finding
Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.
Blue irides
MedGen UID:
500890
Concept ID:
CN000597
Finding
A markedly blue coloration of the iris.
Optic atrophy
MedGen UID:
504537
Concept ID:
CN000609
Finding
Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.
Ocular albinism
MedGen UID:
504729
Concept ID:
CN001040
Finding
An abnormal reduction in the amount of pigmentation (reduced or absent) of the iris and retina.
Hypopigmentation of the fundus
MedGen UID:
506141
Concept ID:
CN006932
Finding
Decreased amount of pigmentation of the retina.
Photophobia
MedGen UID:
504524
Concept ID:
CN000575
Finding
Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.
Freckling
MedGen UID:
5272
Concept ID:
C0016689
Disease or Syndrome
Freckles in sun-exposed areas
MedGen UID:
348494
Concept ID:
C1859923
Finding
Albinism
MedGen UID:
504689
Concept ID:
CN000958
Finding
An abnormal reduction in the amount of pigmentation (reduced or absent) of skin, hair and eye (iris and retina).
Red hair
MedGen UID:
505185
Concept ID:
CN002085
Finding
Neoplasm of the skin
MedGen UID:
428780
Concept ID:
CN007095
Finding
A tumor (abnormal growth of tissue) of the skin.

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
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
Castle D, Kromberg J, Kowalsky R, Moosa R, Gillman N, Zwane E, Fritz V
J Med Genet 1988 Dec;25(12):835-7. PMID: 3148727Free PMC Article

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. [Epub ahead of print] 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. [Epub ahead of print] 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. [Epub ahead of print] 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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