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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
SNOMED CT: OCA2 - Tyrosinase-positive oculocutaneous albinism (26336006); Albinoidism (26336006); Oculocutaneous albinism type 2 (26336006); Tyrosinase-positive oculocutaneous albinism (26336006)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Source: 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 individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
 
Genes (locations): MC1R (16q24.3); OCA2 (15q12-13.1)
 
Monarch Initiative: MONDO:0008746
OMIM®: 203200
Orphanet: ORPHA79432

Definition

Tyrosinase-positive oculocutaneous albinism (OCA, type II; OCA2) 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). [from OMIM]

Additional description

From MedlinePlus Genetics
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).

Several additional types of this disorder have been proposed, each affecting one or a few families.

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.  https://medlineplus.gov/genetics/condition/oculocutaneous-albinism

Clinical features

From HPO
Albinism
MedGen UID:
182
Concept ID:
C0001916
Disease or Syndrome
An abnormal reduction in the amount of pigmentation (reduced or absent) of skin, hair and eye (iris and retina).
Hypopigmentation of the skin
MedGen UID:
102477
Concept ID:
C0162835
Disease or Syndrome
A reduction of skin color related to a decrease in melanin production and deposition.
Red hair
MedGen UID:
66796
Concept ID:
C0239803
Finding
Freckles in sun-exposed areas
MedGen UID:
348494
Concept ID:
C1859923
Finding
Hypopigmentation of hair
MedGen UID:
480031
Concept ID:
C3278401
Finding
Exotropia
MedGen UID:
4613
Concept ID:
C0015310
Disease or Syndrome
A form of strabismus with one or both eyes deviated outward.
Myopia
MedGen UID:
44558
Concept ID:
C0027092
Disease or Syndrome
Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.
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
A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.
Hypopigmentation of the fundus
MedGen UID:
101805
Concept ID:
C0151891
Disease or Syndrome
Reduced pigmentation of the fundus, typically generalized. Fundoscopy may reveal a low level pigment in both RPE and choroid with clear visibility of choroidal vessels (pale/albinoid) or low pigment level in the RPE with deep pigment in choroid so that visible choroidal vessels are separated by deeply pigmented zones (tesselated/tigroid).
Reduced visual acuity
MedGen UID:
65889
Concept ID:
C0234632
Finding
Diminished clarity of vision.
Blue irides
MedGen UID:
108297
Concept ID:
C0578626
Finding
A markedly blue coloration of the iris.
Foveal hypoplasia
MedGen UID:
393047
Concept ID:
C2673946
Finding
Underdevelopment of the fovea centralis.
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.

Professional guidelines

PubMed

Aquaron R, Lasseaux E, Kelekele J, Bonello-Palot N, Badens C, Arveiler B, Tshilolo L
Eur J Med Genet 2022 Oct;65(10):104594. Epub 2022 Aug 12 doi: 10.1016/j.ejmg.2022.104594. PMID: 35964929
White D, Rabago-Smith M
J Hum Genet 2011 Jan;56(1):5-7. Epub 2010 Oct 14 doi: 10.1038/jhg.2010.126. PMID: 20944644

Recent clinical studies

Etiology

Stephen J, Yokoyama T, Tolman NJ, O'Brien KJ, Nicoli ER, Brooks BP, Huryn L, Titus SA, Adams DR, Chen D, Gahl WA, Gochuico BR, Malicdan MC
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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
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Diagnosis

McElvaney OJ, Huizing M, Gahl WA, O'Donovan P, Horan D, Logan PM, Reeves EP, McElvaney NG
Thorax 2018 Nov;73(11):1085-1088. Epub 2018 Jun 25 doi: 10.1136/thoraxjnl-2018-211920. PMID: 29941477Free PMC Article
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
Izquierdo NJ, Townsend W, Hussels IE
Trans Am Ophthalmol Soc 1995;93:191-200; discussion 200-2. doi: 10.1016/s0002-9394(14)70555-0. PMID: 8719678Free PMC Article
Iwata F, Kaiser-Kupfer MI
Curr Opin Ophthalmol 1994 Dec;5(6):79-83. doi: 10.1097/00055735-199412000-00013. PMID: 10150832
van Dorp DB
Clin Genet 1987 Apr;31(4):228-42. doi: 10.1111/j.1399-0004.1987.tb02801.x. 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
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Prognosis

McElvaney OJ, Huizing M, Gahl WA, O'Donovan P, Horan D, Logan PM, Reeves EP, McElvaney NG
Thorax 2018 Nov;73(11):1085-1088. Epub 2018 Jun 25 doi: 10.1136/thoraxjnl-2018-211920. PMID: 29941477Free PMC Article
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
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Colman MA, Stevens G, Ramsay M, Kwon B, Jenkins T
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J Med Genet 1991 Jul;28(7):482-4. doi: 10.1136/jmg.28.7.482. PMID: 1910093Free PMC Article
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Heim RA, Dunn DS, Candy SE, Zwane E, Kromberg JG, Jenkins T
Hum Genet 1988 May;79(1):89. doi: 10.1007/BF00291719. PMID: 3130302

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