Oculocutaneous albinism

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Oculocutaneous albinism
Other namesOCA
Specialty Ophthalmology, dermatology   OOjs UI icon edit-ltr-progressive.svg

Oculocutaneous albinism is a form of albinism involving the eyes ( oculo- ), the skin (-cutaneous ), and the hair. [1] Overall, an estimated 1 in 20,000 people worldwide are born with oculocutaneous albinism. [1] OCA is caused by mutations in several genes that control the synthesis of melanin within the melanocytes. [2] Seven types of oculocutaneous albinism have been described, all caused by a disruption of melanin synthesis and all autosomal recessive disorders. [3] [4] [5] : 864  Oculocutaneous albinism is also found in non-human animals.

Contents

Types

The following types of oculocutaneous albinism have been identified in humans.

Name OMIM GeneDescription
OCA1 203100
606952 		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. [6] The hair is usually white (often translucent) and the skin is very pale. Vision usually ranges from 20/200 to 20/400. The second is OCA1b, which has several subtypes itself. [7] [8] Some individuals with OCA1b can tan and also develop pigment in the hair. [9] 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 points pattern in Siamese cats. [10] ) Another variant of OCA1b, called Albinism, yellow mutant type, is more common among the Amish than in other populations. It results in blonde hair and the eventual development of skin pigmentation during infancy, though at birth is difficult to distinguish from other types. [7] [11] About 1 in 40,000 people have some form of OCA1. [12]
OCA2 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. [9] People with OCA2 usually have fair skin, but are often not as pale as OCA1. They have 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. [13] [12] The gene MC1R does not cause OCA2, but does affect its presentation. [1]
OCA3 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. [14] [12]
OCA4 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. [15] [12] Several German patients were identified in 2004. [16]
OCA5 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. [17] [18]
OCA6 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. [18] [19]
OCA7 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, OMIM: 614537). [18] [20]

See also

Related Research Articles

<span class="mw-page-title-main">Albinism in humans</span> Condition characterized by partial or complete absence of pigment in the skin, hair and eyes

Albinism is a congenital condition characterized in humans by the partial or complete absence of pigment in the skin, hair and eyes. Albinism is associated with a number of vision defects, such as photophobia, nystagmus, and amblyopia. Lack of skin pigmentation makes for more susceptibility to sunburn and skin cancers. In rare cases such as Chédiak–Higashi syndrome, albinism may be associated with deficiencies in the transportation of melanin granules. This also affects essential granules present in immune cells, leading to increased susceptibility to infection.

<span class="mw-page-title-main">Melanin</span> Group of natural pigments found in most organisms

Melanin consist of oligomers or polymers arranged in a disordered manner which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. They have been described as "among the last remaining biological frontiers with the unknown".

<span class="mw-page-title-main">Melanocyte</span> Melanin-producing cells of the skin

Melanocytes are melanin-producing neural crest-derived cells located in the bottom layer of the skin's epidermis, the middle layer of the eye, the inner ear, vaginal epithelium, meninges, bones, and heart. Melanin is a dark pigment primarily responsible for skin color. Once synthesized, melanin is contained in special organelles called melanosomes which can be transported to nearby keratinocytes to induce pigmentation. Thus darker skin tones have more melanosomes present than lighter skin tones. Functionally, melanin serves as protection against UV radiation. Melanocytes also have a role in the immune system.

<span class="mw-page-title-main">Tietz syndrome</span> Congenital disorder

Tietz syndrome, also called Tietz albinism-deafness syndrome or albinism and deafness of Tietz, is an autosomal dominant congenital disorder characterized by deafness and leucism. It is caused by a mutation in the microphthalmia-associated transcription factor (MITF) gene. Tietz syndrome was first described in 1963 by Walter Tietz (1927–2003) a German Physician working in California.

Online Mendelian Inheritance in Man (OMIM) is a continuously updated catalog of human genes and genetic disorders and traits, with a particular focus on the gene-phenotype relationship. As of 28 June 2019, approximately 9,000 of the over 25,000 entries in OMIM represented phenotypes; the rest represented genes, many of which were related to known phenotypes.

<span class="mw-page-title-main">Tyrosinase</span> Enzyme for controlling the production of melanin

Tyrosinase is an oxidase that is the rate-limiting enzyme for controlling the production of melanin. The enzyme is mainly involved in two distinct reactions of melanin synthesis otherwise known as the Raper Mason pathway. Firstly, the hydroxylation of a monophenol and secondly, the conversion of an o-diphenol to the corresponding o-quinone. o-Quinone undergoes several reactions to eventually form melanin. Tyrosinase is a copper-containing enzyme present in plant and animal tissues that catalyzes the production of melanin and other pigments from tyrosine by oxidation. It is found inside melanosomes which are synthesized in the skin melanocytes. In humans, the tyrosinase enzyme is encoded by the TYR gene.

Severe congenital neutropenia (SCN), also often known as Kostmann syndrome or disease, is a group of rare disorders that affect myelopoiesis, causing a congenital form of neutropenia, usually without other physical malformations. SCN manifests in infancy with life-threatening bacterial infections. It causes severe pyogenic infections. It can be caused by autosomal dominant inheritance of the ELANE gene, autosomal recessive inheritance of the HAX1 gene. There is an increased risk of leukemia and myelodysplastic cancers.

<span class="mw-page-title-main">Hermansky–Pudlak syndrome</span> Medical condition

Heřmanský–Pudlák syndrome is an extremely rare autosomal recessive disorder which results in oculocutaneous albinism, bleeding problems due to a platelet abnormality, and storage of an abnormal fat-protein compound. It is thought to affect around 1 in 500,000 people worldwide, with a significantly higher occurrence in Puerto Ricans, with a prevalence of 1 in 1800. Many of the clinical research studies on the disease have been conducted in Puerto Rico.

<span class="mw-page-title-main">Cutis laxa</span> Medical condition

Cutis laxa or pachydermatocele is a group of rare connective tissue disorders in which the skin becomes inelastic and hangs loosely in folds.

<span class="mw-page-title-main">Piebaldism</span> Medical condition

Piebaldism refers to the absence of mature melanin-forming cells (melanocytes) in certain areas of the skin and hair. It is a rare autosomal dominant disorder of melanocyte development. Common characteristics include a congenital white forelock, scattered normal pigmented and hypopigmented macules and a triangular shaped depigmented patch on the forehead. There is nevertheless great variation in the degree and pattern of presentation, even within affected families. In some cases, piebaldism occurs together with severe developmental problems, as in Waardenburg syndrome and Hirschsprung's disease.

Acromicric dysplasia is an extremely rare inherited disorder characterized by abnormally short hands and feet, growth retardation and delayed bone maturation leading to short stature. Most cases have occurred randomly for no apparent reason (sporadically). However, autosomal dominant inheritance has not been ruled out.

<span class="mw-page-title-main">Rothmund–Thomson syndrome</span> Rare autosomal recessive skin condition.

Rothmund–Thomson syndrome (RTS) is a rare autosomal recessive skin condition.

<span class="mw-page-title-main">TYRP1</span> Enzyme

Tyrosinase-related protein 1, also known as TYRP1, is an intermembrane enzyme which in humans is encoded by the TYRP1 gene.

<span class="mw-page-title-main">P protein</span> Protein-coding gene in humans

P protein, also known as melanocyte-specific transporter protein or pink-eyed dilution protein homolog, is a protein that in humans is encoded by the oculocutaneous albinism II (OCA2) gene. The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically of tyrosine—a precursor of melanin. Certain mutations in OCA2 result in type 2 oculocutaneous albinism. OCA2 encodes the human homologue of the mouse p gene.

<span class="mw-page-title-main">Membrane-associated transporter protein</span> Protein

Membrane-associated transporter protein (MATP), also known as solute carrier family 45 member 2 (SLC45A2) or melanoma antigen AIM1, is a protein that in humans is encoded by the SLC45A2 gene.

Oculocutaneous albinism type I or type 1A is an autosomal recessive skin disease. This subtype of oculocutaneous albinism is caused when the gene for tyrosinase does not function properly.

<span class="mw-page-title-main">Ichthyosis follicularis with alopecia and photophobia syndrome</span> Medical condition

IFAP syndrome is an extremely rare genetic syndrome. It is also known as Ichthyosis follicularis, alopecia, and photophobia syndrome or simply ichthyosis follicularis. It is extremely rare: there were only 40 known cases until 2011.

Ichthyosis hystrix is a group of rare skin disorders in the ichthyosis family of skin disorders characterized by massive hyperkeratosis with an appearance like spiny scales. This term is also used to refer to a type of epidermal nevi with extensive bilateral distribution.

<span class="mw-page-title-main">Amelanism</span> Pigmentation abnormality

Amelanism is a pigmentation abnormality characterized by the lack of pigments called melanins, commonly associated with a genetic loss of tyrosinase function. Amelanism can affect fish, amphibians, reptiles, birds, and mammals including humans. The appearance of an amelanistic animal depends on the remaining non-melanin pigments. The opposite of amelanism is melanism, a higher percentage of melanin.

<span class="mw-page-title-main">Albinism</span> Disorder causing lack of pigmentation

Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with the condition are referred to as albinos.

References

  1. 1 2 3 "Oculocutaneous albinism". Genetics Home Reference. U.S. National Library of Medicine . Retrieved 5 August 2020.
  2. ↑ "Orphanet: Oculocutaneous albinism". Orphanet.
  3. ↑ "OMIM Entry - #615179 - ALBINISM, OCULOCUTANEOUS, TYPE VII; OCA7". Online Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 16 June 2020.
  4. ↑ Grønskov K, Ek J, Brondum-Nielsen K (2007). "Oculocutaneous albinism". Orphanet Journal of Rare Diseases. 2. Article 43. doi: 10.1186/1750-1172-2-43 . PMC   2211462 . PMID   17980020.
  5. ↑ James WD, Berger T, Elston DM (2005). Andrews' Diseases of the Skin: Clinical Dermatology (10 ed.). Saunders. ISBN   0-7216-2921-0.
  6. ↑ "OMIM Entry - #203100 - ALBINISM, OCULOCUTANEOUS, TYPE IA; OCA1A". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  7. 1 2 "OMIM Entry - #606952 - ALBINISM, OCULOCUTANEOUS, TYPE IB; OCA1B". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  8. ↑ Mendez, Rodrigo; Iqbal, Sumaiya; Vishnopolska, Sebastián; Martinez, Cinthia; Dibner, Glenda; Aliano, Rocio; Zaiat, Jonathan; Biagioli, Germán; Fernandez, Cecilia; Turjanski, Adrian; Campbell, Arthur J.; Mercado, Graciela; Marti, Marcelo A. (18 February 2021). "Oculocutaneous albinism type 1B associated with a functionally significant tyrosinase gene polymorphism detected with Whole Exome Sequencing". Ophthalmic Genetics. 42 (3): 291–295. doi:10.1080/13816810.2021.1888129. ISSN   1381-6810. PMID   33599182. S2CID   231953047.
  9. 1 2 King RA, Summers G, Haefemeyer JW, LeRoy B (2009). "Facts about Albinism". Archived from the original on 15 February 2009.
  10. ↑ Giebel LB, Tripathi RK, King RA, Spritz RA (March 1991). "A tyrosinase gene missense mutation in temperature-sensitive type I oculocutaneous albinism. A human homologue to the Siamese cat and the Himalayan mouse". The Journal of Clinical Investigation. 87 (3): 1119–1122. doi:10.1172/JCI115075. PMC   329910 . PMID   1900309.
  11. ↑ Peracha MO, Eliott D, Garcia-Valenzuela E (13 September 2005). Gordon K 3rd, Talavera F, Rowsey JJ, Brown LL, Roy H Sr (eds.). "Ocular Manifestations of Albinism". eMedicine . WebMD. Archived from the original on 9 June 2007. Retrieved 31 March 2007.
  12. 1 2 3 4 Boissy RE, Nordlund JJ (22 August 2005). Ortonne JP, Vinson RP, Perry V, Gelfand JM, James WD (eds.). "Albinism". eMedicine . WebMD. Archived from the original on 8 June 2007. Retrieved 31 March 2007.
  13. ↑ "OMIM Entry - #203200 - ALBINISM, OCULOCUTANEOUS, TYPE II; OCA2". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  14. ↑ "OMIM Entry - #203290 - ALBINISM, OCULOCUTANEOUS, TYPE III; OCA3". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  15. ↑ "OMIM Entry - #606574 - ALBINISM, OCULOCUTANEOUS, TYPE IV; OCA4". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  16. ↑ Rundshagen U, Zühlke C, Opitz S, Schwinger E, Käsmann-Kellner B (February 2004). "Mutations in the MATP gene in five German patients affected by oculocutaneous albinism type 4". Human Mutation. 23 (2): 106–110. doi: 10.1002/humu.10311 . PMID   14722913. S2CID   40612241.
  17. ↑ "OMIM Entry - #615312 - ALBINISM, OCULOCUTANEOUS, TYPE V; OCA5". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  18. 1 2 3 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 (January 2014). "Increasing the complexity: new genes and new types of albinism". Pigment Cell & Melanoma Research. 27 (1): 11–18. doi: 10.1111/pcmr.12167 . PMID   24066960.
  19. ↑ "OMIM Entry - #113750 - ALBINISM, OCULOCUTANEOUS, TYPE VI; OCA6". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.
  20. ↑ "OMIM Entry - #615179 - ALBINISM, OCULOCUTANEOUS, TYPE VII; OCA7". Mendelian Inheritance in Man . Johns Hopkins University . Retrieved 5 August 2020.

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