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Oculocutaneous albinism type 1A(OCA1A)

MedGen UID:
82809
Concept ID:
C0268494
Disease or Syndrome
Synonyms: ALBINISM, OCULOCUTANEOUS, TYPE IA; ALBINISM, OCULOCUTANEOUS, TYPE IB; OCA1A; Oculocutaneous Albinism Type 1; Tyrosinase-negative oculocutaneous albinism
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: Tyrosinase-negative oculocutaneous albinism (6483008); OCA1 - Tyrosinase-negative oculocutaneous albinism (6483008); Tyrosinase-related oculocutaneous albinism (6483008)
 
Gene: TYR
Cytogenetic location: 11q14.3
OMIM®: 203100
Orphanet: ORPHA79431

Disease characteristics

Excerpted from the GeneReview: Oculocutaneous Albinism Type 1
Oculocutaneous albinism type 1 (OCA1) is characterized by hypopigmentation of the skin and hair and the distinctive 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 with substantial reduction in visual acuity, usually in the range of 20/100 to 20/400; and misrouting of the optic nerve fiber radiations at the chiasm, resulting in strabismus, reduced stereoscopic vision, and altered visually evoked potentials (VEP). Individuals with OCA1A have white hair, white skin that does not tan, and fully translucent irides, none of which darken with age. At birth, individuals with OCA1B have white or very light yellow hair that darkens minimally with age, white skin that over time develops some minimal generalized pigment and may tan slightly with judicious sun exposure, and blue irides that darken to green/hazel or light brown/tan with age, although transillumination defects persist. Visual acuity may be 20/60 or better in some eyes.  [from GeneReviews]
Full text of GeneReview (by section):
Summary  |  GeneReview Scope  |  Diagnosis  |  Clinical Description  |  Differential Diagnosis  |  Management  |  Genetic Counseling  |  Resources  |  Molecular Genetics  |  References  |  Chapter Notes
Authors:
Richard Alan Lewis   view full author information

Additional description

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

Neoplasm of the skin
MedGen UID:
428780
Concept ID:
CN007095
Finding
A neoplasm 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.).
Abnormality of vision evoked potentials
MedGen UID:
105509
Concept ID:
C0522214
Finding
Nystagmus
MedGen UID:
409575
Concept ID:
C1963184
Finding
Foveal hypoplasia
MedGen UID:
393047
Concept ID:
C2673946
Finding
Astigmatism
MedGen UID:
504459
Concept ID:
CN000451
Finding
Astigmatism describes a refractive error characterized by a difference in the horizontal and vertical curvature of the cornea.
Myopia
MedGen UID:
504487
Concept ID:
CN000511
Finding
An abnormality of refraction characterized by the ability to see objects nearby clearly, while objects in the distance appear blurry.
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.
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.
Aplasia/Hypoplasia of the corpus callosum
MedGen UID:
425895
Concept ID:
CN006451
Finding
Absence or underdevelopment of the corpus callosum.
Reduced bone mineral density
MedGen UID:
393152
Concept ID:
C2674432
Finding
Freckling
MedGen UID:
5272
Concept ID:
C0016689
Disease or Syndrome
Absent skin pigmentation
MedGen UID:
393051
Concept ID:
C2673954
Finding
Hyperkeratosis
MedGen UID:
504662
Concept ID:
CN000900
Finding
Hyperkeratosis is thickening of the outer layer of the skin, the stratum corneum, which is composed of large, polyhedral, plate-like envelopes filled with keratin which are the dead cells that have migrated up from the stratum granulosum.
Generalized hypopigmentation
MedGen UID:
425911
Concept ID:
CN006589
Finding
Neoplasm of the skin
MedGen UID:
428780
Concept ID:
CN007095
Finding
A neoplasm of the skin.
White hair
MedGen UID:
506568
Concept ID:
CN167092
Finding
Hypopigmented hair that appears white.

Recent clinical studies

Etiology

Karaman A
Dermatol Online J 2008 Nov 15;14(11):13. PMID: 19094851
Hoffmann MB, Wolynski B, Meltendorf S, Behrens-Baumann W, Käsmann-Kellner B
Invest Ophthalmol Vis Sci 2008 Jun;49(6):2756-64. Epub 2008 Feb 22 doi: 10.1167/iovs.07-1461. [Epub ahead of print] PMID: 18296661

Diagnosis

Karaman A
Dermatol Online J 2008 Nov 15;14(11):13. PMID: 19094851
Hoffmann MB, Wolynski B, Meltendorf S, Behrens-Baumann W, Käsmann-Kellner B
Invest Ophthalmol Vis Sci 2008 Jun;49(6):2756-64. Epub 2008 Feb 22 doi: 10.1167/iovs.07-1461. [Epub ahead of print] PMID: 18296661

Clinical prediction guides

K B, Purohit R
Gene 2013 Jan 15;513(1):184-95. Epub 2012 Oct 22 doi: 10.1016/j.gene.2012.09.128. [Epub ahead of print] PMID: 23085273
Hoffmann MB, Wolynski B, Meltendorf S, Behrens-Baumann W, Käsmann-Kellner B
Invest Ophthalmol Vis Sci 2008 Jun;49(6):2756-64. Epub 2008 Feb 22 doi: 10.1167/iovs.07-1461. [Epub ahead of print] PMID: 18296661

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