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Oculocutaneous albinism type 4(OCA4)

MedGen UID:
338324
Concept ID:
C1847836
Disease or Syndrome
Synonyms: Albinism, oculocutaneous, type IV; OCA4
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): SLC45A2 (5p13.2)
OMIM®: 606574
Orphanet: ORPHA79435

Definition

Oculocutaneous albinism type 4 (OCA4) is characterized by hypopigmentation of the hair and skin plus the characteristic ocular changes found in all other 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 nerves at the chiasm associated with alternating strabismus, reduced stereoscopic vision, and an altered visual evoked potential (VEP). Individuals with OCA4 are usually recognized within the first year of life because of hypopigmentation of the hair and skin and the ocular features of nystagmus and strabismus. Vision is likely to be stable after early childhood. The amount of cutaneous pigmentation in OCA4 ranges from minimal to near normal. Newborns with OCA4 usually have some pigment in their hair, with color ranging from silvery white to light yellow. Hair color may darken with time, but does not vary significantly from childhood to adulthood. [from GTR]

Additional descriptions

From GeneReviews
Oculocutaneous albinism type 4 (OCA4) is characterized by hypopigmentation of the hair and skin plus the characteristic ocular changes found in all other 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 nerves at the chiasm associated with alternating strabismus, reduced stereoscopic vision, and an altered visual evoked potential (VEP). Individuals with OCA4 are usually recognized within the first year of life because of hypopigmentation of the hair and skin and the ocular features of nystagmus and strabismus. Vision is likely to be stable after early childhood. The amount of cutaneous pigmentation in OCA4 ranges from minimal to near normal. Newborns with OCA4 usually have some pigment in their hair, with color ranging from silvery white to light yellow. Hair color may darken with time, but does not vary significantly from childhood to adulthood.  https://www.ncbi.nlm.nih.gov/books/NBK1510
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
Involuntary movements of the eye that are divided into two types, jerk and pendular. Jerk nystagmus has a slow phase in one direction followed by a corrective fast phase in the opposite direction, and is usually caused by central or peripheral vestibular dysfunction. Pendular nystagmus features oscillations that are of equal velocity in both directions and this condition is often associated with visual loss early in life. (Adams et al., Principles of Neurology, 6th ed, p272)
Hypopigmentation of the fundus
MedGen UID:
101805
Concept ID:
C0151891
Disease or Syndrome
Decreased amount of pigmentation of the retina.
Blue irides
MedGen UID:
108297
Concept ID:
C0578626
Finding
A markedly blue coloration of the iris.
Macular hypoplasia
MedGen UID:
340322
Concept ID:
C1849412
Finding
Underdevelopment of the macula lutea.
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.
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

Etiology

Tóth L, Fábos B, Farkas K, Sulák A, Tripolszki K, Széll M, Nagy N
BMC Med Genet 2017 Mar 15;18(1):27. doi: 10.1186/s12881-017-0386-7. PMID: 28298193Free PMC Article
Graf J, Voisey J, Hughes I, van Daal A
Hum Mutat 2007 Jul;28(7):710-7. doi: 10.1002/humu.20504. PMID: 17358008
Inagaki K, Suzuki T, Ito S, Suzuki N, Adachi K, Okuyama T, Nakata Y, Shimizu H, Matsuura H, Oono T, Iwamatsu H, Kono M, Tomita Y
Pigment Cell Res 2006 Oct;19(5):451-3. doi: 10.1111/j.1600-0749.2006.00332.x. PMID: 16965274
Inagaki K, Suzuki T, Shimizu H, Ishii N, Umezawa Y, Tada J, Kikuchi N, Takata M, Takamori K, Kishibe M, Tanaka M, Miyamura Y, Ito S, Tomita Y
Am J Hum Genet 2004 Mar;74(3):466-71. Epub 2004 Feb 11 doi: 10.1086/382195. PMID: 14961451Free PMC Article
Rundshagen U, Zühlke C, Opitz S, Schwinger E, Käsmann-Kellner B
Hum Mutat 2004 Feb;23(2):106-10. doi: 10.1002/humu.10311. PMID: 14722913

Diagnosis

Oki R, Yamada K, Nakano S, Kimoto K, Yamamoto K, Kondo H, Kubota T
Invest Ophthalmol Vis Sci 2017 Feb 1;58(2):1008-1016. doi: 10.1167/iovs.16-20612. PMID: 28192564
Fernandez BA, Green JS, Bursey F, Barrett B, MacMillan A, McColl S, Fernandez S, Rahman P, Mahoney K, Pereira SL, Scherer SW, Boycott KM, Woods MO; FORGE Canada Consortium.
BMC Med Genet 2012 Nov 21;13:111. doi: 10.1186/1471-2350-13-111. PMID: 23171239Free PMC Article
Verhagen JM, Huijmans JG, Williams M, van Ruyven RL, Bergen AA, Wouters CH, Brooks AS
Am J Med Genet A 2012 Nov;158A(11):2931-4. Epub 2012 Sep 17 doi: 10.1002/ajmg.a.35611. PMID: 22987308

Clinical prediction guides

Oki R, Yamada K, Nakano S, Kimoto K, Yamamoto K, Kondo H, Kubota T
Invest Ophthalmol Vis Sci 2017 Feb 1;58(2):1008-1016. doi: 10.1167/iovs.16-20612. PMID: 28192564

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