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| {{Infobox medical condition (new) | | |
| | name = | | {{Infobox medical condition |
| | image = | | | name = Oculocutaneous albinism |
| | caption =
| | | synonyms = OCA |
| | pronounce =
| | | field = [[Dermatology]], [[Genetics]] |
| | field = | | | symptoms = [[Hypopigmentation]] of the skin, hair, and eyes |
| | synonyms = OCA
| | | complications = [[Vision impairment]], [[Skin cancer]] |
| | symptoms = | | | onset = Congenital |
| | complications = | | | duration = Lifelong |
| | onset = | | | types = OCA1, OCA2, OCA3, OCA4 |
| | duration = | | | causes = [[Genetic mutation]] |
| | types = | | | risks = Increased risk of [[skin cancer]] |
| | causes = | | | diagnosis = [[Genetic testing]], [[Ophthalmologic examination]] |
| | risks = | | | differential = [[Hermansky–Pudlak syndrome]], [[Chediak–Higashi syndrome]] |
| | diagnosis = | | | prevention = None |
| | differential = | | | treatment = [[Sun protection]], [[Vision aids]] |
| | prevention = | | | frequency = 1 in 20,000 |
| | treatment = | |
| | medication =
| |
| | prognosis =
| |
| | frequency = | |
| | deaths =
| |
| }} | | }} |
| '''Oculocutaneous albinism''' is a form of [[albinism]] involving the [[human eye|eye]]s (''[[wikt:oculo-#Prefix|oculo-]]''), the [[human skin|skin]] (''-[[wikt:cutaneous#Adjective|cutaneous]]''), and according to some definitions, the [[hair]].<ref name="urlOculocutaneous albinism - Genetics Home Reference">{{Cite web|url=http://ghr.nlm.nih.gov/condition=oculocutaneousalbinism |title=Oculocutaneous albinism – Genetics Home Reference |format= |website= |accessdate=}}</ref> | | {{Short description|A group of genetic conditions affecting pigmentation in the skin, hair, and eyes}} |
| Overall, an estimated 1 in 20,000 people worldwide are born with oculocutaneous albinism.<ref>{{Cite web | url=http://ghr.nlm.nih.gov/condition/oculocutaneous-albinism |title = Oculocutaneous albinism}}</ref> OCA is caused by [[mutation]]s in several [[gene]]s that control the [[biosynthesis|synthesis]] of [[melanin]] within the [[melanocyte]]s.<ref>{{Cite web | url=http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=55 | title=Orphanet: Oculocutaneous albinism}}</ref>
| | '''Oculocutaneous albinism''' (OCA) is a group of rare [[genetic disorders]] characterized by a reduction or complete lack of [[melanin]] pigment in the [[skin]], [[hair]], and [[eyes]]. This condition affects individuals of all ethnic backgrounds and is associated with vision problems and increased risk of skin damage due to sun exposure. |
| Four types of oculocutaneous albinism have been described, all caused by a disruption of melanin synthesis and all [[autosomal recessive]] disorders.<ref name="pmid17980020">{{Cite journal|vauthors=Grønskov K, Ek J, Brondum-Nielsen K |title=Oculocutaneous albinism |journal=Orphanet Journal of Rare Diseases |volume=2 |issue= |pages=43 |year=2007 |pmid=17980020 |pmc=2211462 |doi=10.1186/1750-1172-2-43}}</ref><ref name="Andrews">James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. {{ISBN|0-7216-2921-0}}.</ref>{{Rp|864}}
| |
| | |
| ==Types== | | ==Types== |
| {| class="wikitable" style="clear: both;"
| | Oculocutaneous albinism is classified into several types based on the specific genetic mutations involved. The most common types include: |
| | '''Name''' || '''[[OMIM]]''' || '''Gene''' || '''Description'''
| | ===OCA1=== |
| |-
| | OCA1 is caused by mutations in the [[TYR]] gene, which encodes the enzyme [[tyrosinase]]. This enzyme is crucial for the production of melanin. OCA1 is further divided into two subtypes: |
| | OCA1 || {{OMIM2|203100}}<br>{{OMIM2|606952}} || [[tyrosinase|TYR]] || OCA1 is caused by mutations of the [[tyrosinase]] gene, and can occur in two variations. The first is '''OCA1a''', and means that the organism cannot synthesize melanin whatsoever.<ref>[https://omim.org/entry/203100 OCA1A page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref> The hair is usually white (often translucent) and the skin very pale. Vision usually ranges from 20/200 to 20/400. The second is '''OCA1b''', which has several subtypes itself.<ref name="OMIM OCA2B">[https://omim.org/entry/606952 OCA1B page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref> Some individuals with OCA1b can tan and also develop pigment in the hair.<ref name="Facts_Albinism">[https://web.archive.org/web/20090215051759/http://albinism.med.umn.edu/facts.htm "Facts about Albinism" (archived)], by Dr. Richard King et al., 2009</ref> One subtype of OCA1b is called '''OCA1b TS''' (temperature sensitive), where the [[tyrosinase]] can only function below a certain temperature, which causes the body hair in cooler body regions to develop pigment (i.e. get darker). (An equivalent mutation produces the coat pattern in [[Siamese (cat)|Siamese cats]].<ref>{{Cite journal|vauthors=Giebel LB, Tripathi RK, King RA, Spritz RA |title=A tyrosinase gene missense mutation in temperature-sensitive type I oculocutaneous albinism. A human homologue to the Siamese cat and the Himalayan mouse |journal=The Journal of Clinical Investigation |volume=87 |issue=3 |pages=1119–22 |date=March 1991 |pmid=1900309 |pmc=329910 |doi=10.1172/JCI115075}}</ref>) Another variant of OCA1b, called '''Albinism, yellow mutant type''' is more common among the [[Amish]] than in other populations, and results in blonde hair and the eventual development of skin pigmentation during infancy, though at birth is difficult to distinguish from other types.<ref name="OMIM OCA2B" /><ref name="eMedicine2">[http://www.emedicine.com/oph/topic260.htm "Ocular Manifestations of Albinism"], by Dr. Mohammed O. Peracha, at [[eMedicine]], 13 September 2005; retrieved 31 March 2007</ref> About 1 in 40,000 people have some form of OCA1.<ref name="eMedicine1">[http://www.emedicine.com/derm/topic12.htm "Albinism"], by Dr. Raymond E. Boissy, Dr. James J. Nordlund, et al., at [[eMedicine]], 22 August 2005; retrieved 31 March 2007</ref>
| | * '''OCA1A''': Characterized by a complete absence of tyrosinase activity, resulting in no melanin production. Individuals with OCA1A have white hair, very pale skin, and light-colored eyes. |
| |-
| | * '''OCA1B''': Involves reduced tyrosinase activity, allowing for some melanin production. Individuals may have light blonde hair and slightly more pigmentation in the skin and eyes compared to OCA1A. |
| | OCA2 || {{OMIM2|203200}} || [[OCA2]] || The most common type of albinism, is caused by mutation of the P gene. People with OCA2 generally have more pigment and better vision than those with OCA1, but cannot tan like some with OCA1b. A little pigment can develop in freckles or moles.<ref name="Facts_Albinism"/> People with OCA2 usually have fair skin but often not as pale as OCA1, and pale blonde to golden, strawberry blonde, or even brown hair, and most commonly blue eyes. Affected people of African descent usually have a different [[phenotype]] (appearance): yellow hair, pale skin, and blue, gray or hazel eyes. About 1 in 15,000 people have OCA2.<ref>[https://omim.org/entry/203200 OCA2 page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref><ref name="eMedicine1" /> The gene [[MC1R]] doesn't cause OCA2, but does affect its presentation.<ref name="urlOculocutaneous albinism - Genetics Home Reference"/>
| | ===OCA2=== |
| |-
| | OCA2 is the most common form of albinism worldwide and is caused by mutations in the [[OCA2]] gene. This gene is involved in the transport of tyrosine, a precursor to melanin, into the melanosomes. Individuals with OCA2 typically have light skin and hair, but more pigmentation than those with OCA1. |
| | OCA3 || {{OMIM2|203290}} || [[TYRP1]] || Has only been partially researched and documented. It is caused by mutation of the tyrosinase-related protein-1 (Tyrp1) gene. Cases have been reported in Africa and New Guinea. Affected individuals typically have red hair, reddish-brown skin and blue or gray eyes. Variants may include '''rufous oculocutaneous albinism''' ('''ROCA''' or '''xanthism'''). The incidence rate of OCA3 is unknown.<ref>[https://omim.org/entry/203290 OCA3 page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref><ref name="eMedicine1" />
| | ===OCA3=== |
| |-
| | OCA3 is caused by mutations in the [[TYRP1]] gene, which encodes the enzyme tyrosinase-related protein 1. This type is more common in individuals of African descent and results in reddish-brown skin, hair, and eye color. |
| | OCA4 || {{OMIM2|606574}} || [[SLC45A2]] || Is very rare outside Japan, where OCA4 accounts for 24% of albinism cases. OCA4 can only be distinguished from OCA2 through genetic testing, and is caused by mutation of this membrane-associated transporter protein (MATP) gene.<ref>[https://omim.org/entry/606574 OCA4 page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref><ref name="eMedicine1" /> Several German patients were identified in 2004.<ref>{{Cite journal|vauthors=Rundshagen U, Zühlke C, Opitz S, Schwinger E, Käsmann-Kellner B |title=Mutations in the MATP gene in five German patients affected by oculocutaneous albinism type 4 |journal=Human Mutation |volume=23 |issue=2 |pages=106–10 |date=February 2004 |pmid=14722913 |doi=10.1002/humu.10311}}</ref>
| | ===OCA4=== |
| |-
| | OCA4 is caused by mutations in the [[SLC45A2]] gene, which is involved in melanin production. This type is more prevalent in certain populations, such as those of East Asian descent, and results in a phenotype similar to OCA2. |
| | OCA5 || {{OMIM2|615312}} || || OCA5 was identified in a Pakistani family with "golden-colored hair, white skin, nystagmus, photophobia, foveal hypoplasia, and impaired visual acuity, regardless of their sex and age". Genetic analysis localized the defect to human chromosome region 4q24, but failed to identify a candidate gene.<ref>[https://omim.org/entry/615312 OCA5 page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref><ref name="Montuliu">{{cite journal| vauthors=Montoliu L, Grønskov K, Wei A, Martínez-García M, Fernández A, Arveiler B, Morice-Picard F, Riazuddin S, Suzuki T, Ahmed Z, Rosenberg T, Li W| title=Increasing the complexity: new genes and new types of albinism |journal=Pigment Cell & Melanoma Research|volume=27 | issue=1 |pages=11–18|date=January 2014 |pmid=24066960 |doi=10.1111/pcmr.12167}}</ref>
| | ==Symptoms== |
| |-
| | The primary symptoms of oculocutaneous albinism include: |
| | OCA6 || {{OMIM2|113750}} || [[SLC24A5]] || One of the rarest forms of OCA, OCA6 was detected in Chinese individuals but is not thought to be limited to this ethnicity. It is heterogeneous in its effect of hair color, and results from mutations in the SLC24A5 gene, a membrane transporter that plays a role in pigmentation in a range of vertebrate species.<ref name="Montuliu" /><ref>[https://omim.org/entry/113750 SHEP4 page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref>
| | * '''Hypopigmentation''': Reduced pigmentation in the skin, hair, and eyes. |
| |-
| | * '''Vision problems''': Including [[nystagmus]] (involuntary eye movements), [[strabismus]] (misalignment of the eyes), [[photophobia]] (sensitivity to light), and reduced visual acuity. |
| | OCA7 || {{OMIM2|615179}} || [[C10orf11]] || OCA7 was originally characterized in a family from the Faroe Islands, but was subsequently identified in a Lithuanian patient. It is characterized by lighter pigmentation, and significant effects on the eye, including decreased visual acuity and misrouting of neuronal tracks through the optic chiasm. It is due to mutation of a gene of unknown function, C10orf11 (11th uncharacterized [[open reading frame]] on chromosome 10, {{OMIM3|614537}}).<ref name="Montuliu" /><ref>[https://omim.org/entry/615179 OCA7 page] at Online ''[[Mendelian Inheritance in Man]]'' Database, [[Johns Hopkins University]]</ref>
| | * '''Increased risk of skin damage''': Due to lack of melanin, individuals are more susceptible to [[sunburn]] and [[skin cancer]]. |
| |-
| | ==Diagnosis== |
| |}
| | Diagnosis of oculocutaneous albinism is based on clinical evaluation, family history, and genetic testing. Eye examinations can reveal characteristic changes in the retina and optic nerve. Genetic testing can confirm the specific type of OCA by identifying mutations in the associated genes. |
| | | ==Management== |
| == See also == | | There is no cure for oculocutaneous albinism, but management focuses on protecting the skin and eyes from sun damage and addressing vision problems. This includes: |
| * [[Piebaldism]] | | * '''Sun protection''': Using sunscreen, wearing protective clothing, and avoiding excessive sun exposure. |
| * [[List of skin conditions]] | | * '''Vision aids''': Prescription glasses, contact lenses, and low vision aids can help improve visual function. |
| * [[List of cutaneous conditions associated with increased risk of nonmelanoma skin cancer]] | | * '''Regular eye exams''': To monitor and manage vision problems. |
| | | ==Related pages== |
| ==References==
| | * [[Albinism]] |
| {{Reflist}}
| | * [[Genetic disorder]] |
| == External links ==
| | * [[Melanin]] |
| {{Medical resources
| | * [[Photophobia]] |
| | DiseasesDB =
| | [[Category:Genetic disorders]] |
| | ICD10 = {{ICD10|E|70|3|e|70}}
| | [[Category:Skin conditions]] |
| | ICD9 = {{ICD9|270.2}}
| | [[Category:Eye diseases]] |
| | ICDO =
| |
| | OMIM = 203100
| |
| | OMIM_mult = {{OMIM2|203200}} {{OMIM2|203290}} {{OMIM2|606574}}
| |
| | MedlinePlus =
| |
| | eMedicineSubj =
| |
| | eMedicineTopic =
| |
| | MeshID = D016115
| |
| | GeneReviewsNBK = NBK1166
| |
| | GeneReviewsName = Oculocutaneous Albinism Type 1
| |
| | ICD10CM = {{ICD10CM|E70.32}}
| |
| | Orphanet = 55
| |
| }}
| |
| | |
| * [http://rarediseases.org/rare-diseases/oculocutaneous-albinism/ Oculocutaneous albinism information] at RareDiseases.org | |
| * [https://www.ncbi.nlm.nih.gov/gtr/all/tests/?term=albinism/ NCBI Genetic Testing Registry]
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| {{Amino acid metabolic pathology}}
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| {{Pigmentation disorders}}
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| {{Use dmy dates|date=August 2019}}
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| {{DEFAULTSORT:Oculocutaneous Albinism}}
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| [[Category:Amino acid metabolism disorders]] | |
| [[Category:Albinism]] | |
| [[Category:Autosomal recessive disorders]] | |
| {{dictionary-stub1}}
| |
| Oculocutaneous albinism
|
|
|
| Synonyms
|
OCA
|
| Pronounce
|
N/A
|
| Specialty
|
N/A
|
| Symptoms
|
Hypopigmentation of the skin, hair, and eyes
|
| Complications
|
Vision impairment, Skin cancer
|
| Onset
|
Congenital
|
| Duration
|
Lifelong
|
| Types
|
OCA1, OCA2, OCA3, OCA4
|
| Causes
|
Genetic mutation
|
| Risks
|
Increased risk of skin cancer
|
| Diagnosis
|
Genetic testing, Ophthalmologic examination
|
| Differential diagnosis
|
Hermansky–Pudlak syndrome, Chediak–Higashi syndrome
|
| Prevention
|
None
|
| Treatment
|
Sun protection, Vision aids
|
| Medication
|
N/A
|
| Prognosis
|
N/A
|
| Frequency
|
1 in 20,000
|
| Deaths
|
N/A
|
A group of genetic conditions affecting pigmentation in the skin, hair, and eyes
Oculocutaneous albinism (OCA) is a group of rare genetic disorders characterized by a reduction or complete lack of melanin pigment in the skin, hair, and eyes. This condition affects individuals of all ethnic backgrounds and is associated with vision problems and increased risk of skin damage due to sun exposure.
Oculocutaneous albinism is classified into several types based on the specific genetic mutations involved. The most common types include:
OCA1 is caused by mutations in the TYR gene, which encodes the enzyme tyrosinase. This enzyme is crucial for the production of melanin. OCA1 is further divided into two subtypes:
- OCA1A: Characterized by a complete absence of tyrosinase activity, resulting in no melanin production. Individuals with OCA1A have white hair, very pale skin, and light-colored eyes.
- OCA1B: Involves reduced tyrosinase activity, allowing for some melanin production. Individuals may have light blonde hair and slightly more pigmentation in the skin and eyes compared to OCA1A.
OCA2 is the most common form of albinism worldwide and is caused by mutations in the OCA2 gene. This gene is involved in the transport of tyrosine, a precursor to melanin, into the melanosomes. Individuals with OCA2 typically have light skin and hair, but more pigmentation than those with OCA1.
OCA3 is caused by mutations in the TYRP1 gene, which encodes the enzyme tyrosinase-related protein 1. This type is more common in individuals of African descent and results in reddish-brown skin, hair, and eye color.
OCA4 is caused by mutations in the SLC45A2 gene, which is involved in melanin production. This type is more prevalent in certain populations, such as those of East Asian descent, and results in a phenotype similar to OCA2.
Symptoms[edit]
The primary symptoms of oculocutaneous albinism include:
- Hypopigmentation: Reduced pigmentation in the skin, hair, and eyes.
- Vision problems: Including nystagmus (involuntary eye movements), strabismus (misalignment of the eyes), photophobia (sensitivity to light), and reduced visual acuity.
- Increased risk of skin damage: Due to lack of melanin, individuals are more susceptible to sunburn and skin cancer.
Diagnosis[edit]
Diagnosis of oculocutaneous albinism is based on clinical evaluation, family history, and genetic testing. Eye examinations can reveal characteristic changes in the retina and optic nerve. Genetic testing can confirm the specific type of OCA by identifying mutations in the associated genes.
Management[edit]
There is no cure for oculocutaneous albinism, but management focuses on protecting the skin and eyes from sun damage and addressing vision problems. This includes:
- Sun protection: Using sunscreen, wearing protective clothing, and avoiding excessive sun exposure.
- Vision aids: Prescription glasses, contact lenses, and low vision aids can help improve visual function.
- Regular eye exams: To monitor and manage vision problems.
Related pages[edit]
