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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; Yellow albinism
SNOMED CT: Yellow oculocutaneous albinism (82342003); Yellow mutant oculocutaneous albinism (82342003); Amish albinism (82342003); Yellow-type albinism (82342003); Xanthous albinism (82342003)
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).
 
Gene (location): TYR (11q14.3)
 
Monarch Initiative: MONDO:0011749
OMIM®: 606952
Orphanet: ORPHA79434

Definition

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. [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).

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

Clinical features

From HPO
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.
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.
Hypopigmentation of hair
MedGen UID:
480031
Concept ID:
C3278401
Finding
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.
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).
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.

Term Hierarchy

Recent clinical studies

Diagnosis

Loftus SK, Gillis MF, Lundh L, Baxter LL, Wedel JC, Watkins-Chow DE, Donovan FX; NISC Comparative Sequencing Program, Sergeev YV, Oetting WS, Pavan WJ, Adams DR
Am J Hum Genet 2023 Jul 6;110(7):1123-1137. Epub 2023 Jun 15 doi: 10.1016/j.ajhg.2023.05.012. PMID: 37327787Free PMC Article
Mendez R, Iqbal S, Vishnopolska S, Martinez C, Dibner G, Aliano R, Zaiat J, Biagioli G, Fernandez C, Turjanski A, Campbell AJ, Mercado G, Marti MA
Ophthalmic Genet 2021 Jun;42(3):291-295. Epub 2021 Feb 18 doi: 10.1080/13816810.2021.1888129. PMID: 33599182

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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