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Oculocutaneous albinism type 1B(OCA1B)

MedGen UID:
337712
Concept ID:
C1847024
Disease or Syndrome
Synonyms: ALBINISM, OCULOCUTANEOUS, TYPE IB; Albinism, yellow mutant type; OCA1B; Oculocutaneous Albinism Type 1; Yellow albinism
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)
 
Gene (location): TYR (11q14.3)
OMIM®: 606952
Orphanet: ORPHA79434

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]
Authors:
Richard Alan Lewis   view full author information

Additional descriptions

From OMIM
Oculocutaneous albinism type I is an autosomal recessive disorder characterized by absence of pigment in hair, skin, and eyes, and does not vary with race or age. Severe nystagmus, photophobia, and reduced visual acuity are common features. OCA type I is divided into 2 types: type IA, characterized by complete lack of tyrosinase activity due to production of an inactive enzyme, and type IB, characterized by reduced activity of tyrosinase. Although OCA caused by mutations in the TYR gene was classically known as 'tyrosinase-negative' OCA, Tripathi et al. (1992) noted that some patients with 'tyrosinase-positive' OCA may indeed have TYR mutations resulting in residual enzyme activity. These patients can be classified as having OCA1B.  http://www.omim.org/entry/606952
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.
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.
Hypopigmentation of the fundus
MedGen UID:
101805
Concept ID:
C0151891
Disease or Syndrome
Decreased amount of pigmentation of the retina.
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.
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.
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.
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).
Hypopigmentation of hair
MedGen UID:
480031
Concept ID:
C3278401
Finding

Recent clinical studies

Clinical prediction guides

Dijkstal JM, Cooley SS, Holleschau AM, King RA, Summers CG
J Pediatr Ophthalmol Strabismus 2012 Mar-Apr;49(2):81-6; quiz 87. Epub 2011 Jul 6 doi: 10.3928/01913913-20110628-02. PMID: 21732575

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