DefinitionThis section has been translated automatically.
Group of genetically different, almost exclusively autosomal-recessive inherited metabolic diseases characterized by diffuse hypopigmentation in skin, hair and eyes; caused by partial or complete absence of melanin in the melanocytes The number of epidermal and follicular melanocytes is normal.
ClassificationThis section has been translated automatically.
7 types are differentiated based on molecular differences:
- OCA 1 (tyrosinase-negative OCA): Based on reduced or absent tyrosinase activity; approximately 80 mutations in the tyrosinase gene(TYR) have been described to date. OCA1A is the classic tyrosinase-negative oculocutaneous albinism; OCA 1B is also known as yellow albinism. OCA1Ts refers to temperature-sensitive oculocutaneous albinism (hair on cooler parts of the body darkens with age)
- OCA 2 (tyrosinase-positive OCA): Caused by mutations in the P gene; the role of the P protein is still unclear; regulation of pH in melanosomes? OCA 2 is also called brown albinism or brown African albinism.
- OCA 3 (OMIM 203290)- Red albinism: Caused by mutations in the "tyrosinase-related protein" gene(TYRP1 gene; the Tyrp1 protein is a melanocyte-specific gene product involved in eumelanin synthesis). OCA3 is associated with only mild ocular symptoms. Often remains clinically undetected. Frequently described in African American ethnic groups.
- OCA 4 (OMIM 606574): Caused by mutations in a "membrane associated transporter protein" gene(SLC24A5 gene) that encodes a transport protein for melanin precursors. Variable clinical symptoms comparable to OCA type 2. Common in Korea and Japan.
- OCA 5: OCA 5 has been described in a Pakistani family (white skin, golden hair, and eye symptoms). The gene is still unknown; it could be assigned to chromosomal locus 4q24, a gene locus likely coding for lysosomal proteins (Kausar T et al. 2013).
- OCA 6: In OCA 6, as in OCA 4, a mutation of a transporter protein is present (chromosome 15q21.1).
- In OCA7 (OMIM: 614537), a mutation was found in the"LRMDA gene" which is located on chromosome 10q 22.2-22.3. This gene encodes a protein that is significant for melanocyte differentiation. This rather mild variant was described in a consanguineous Faroese family (Gronskov K et al. (2013).
Further OCA genotypes are expected in the future.
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Occurrence/EpidemiologyThis section has been translated automatically.
Most common inherited disease with diffuse hypomelanosis of the skin. The prevalence is estimated at 1:17,000 - 1:20,000 inhabitants; for some African strains it is 1:1,500 inhabitants.
For the tyrosine negative subtype OCA1 (affects 40% of all forms of albnism) the estimated prevalence in the European population is 1:40,000.
The tyrosine-positive subtype OCA2 (affects 50% of all forms of albnism worldwide) occurs predominantly in the African population. In South Africa and Tanzania, the prevalence is 1:1,400 to 1:10,000 inhabitants (cited in Kubash A 2017)
EtiopathogenesisThis section has been translated automatically.
All types of oculocutaneous albinism (OCA) are based on an autosomal recessive inheritance mechanism, except for a few families with autosomal dominant OCA. The disease is caused by mutations that directly affect the tyrosine singing TYR, or genes of proteins that regulate the processing of the copper-containing enzyme tyrosinase and the biosynthesis of melanin in melanosomes and the secretion of mature melanosomes into the epidermis (cited in Kubasch A et al. 2017).
TherapyThis section has been translated automatically.
Despite various preclinical approaches (e.g. tyrosinase gene transfer, etc.), the only therapeutic options remaining are strict physical and chemical sun protection. Regular dermatological check-ups are necessary (incidences of basal cell carcinoma and squamous cell carcinoma are significantly increased, but not of malignant melanoma).
Note(s)This section has been translated automatically.
LiteratureThis section has been translated automatically.
- Baxter LL, Pavan WJ (2002) The oculocutaneous albinism type IV gene Matp is a new marker of pigment cell precursors during mouse embryonic development. Mech Dev 116: 209-212
- Gronskov K et al (2013) Mutations in C10orf11, a melanocyte-differentiation gene, cause autosomal-recessive albinism. Am J Hum Genet 92: 415-421.
- Kamaraj B et al.(2014) Mutational analysis of oculocutaneous albinism: a compact review. Biomed Res Int doi: 10.1155/2014/905472.
- Kausar T et al. (2013) OCA5, a novel locus for non-syndromic oculocutaneous albinism, maps to chromosome 4q24. Clin Genet 84:91-93.
- King RA et al (2003) Tyrosinase gene mutations in oculocutaneous albinism 1 (OCA1): definition of the phenotype. Hum Genet 113: 502-513
- Kubasch A et al (2017) Oculocutaneous and ocular albinism. Dermatologist 68: 867-875
- King RA et al (2003) MC1R mutations modify the classic phenotype of oculocutaneous albinism type 2 (OCA2). Am J Hum Genet 73: 638-645.
- Nakamura E et al (2002) A novel mutation of the tyrosinase gene causing oculocutaneous albinism type 1 (OCA1). J Dermatol Sci 28: 102-105.
- Oetting WS et al (2003) Oculocutaneous albinism type 1: the last 100 years. Pigment Cell Res 16: 307-311.
- Okulicz JF et al (2003) Oculocutaneous albinism. J Eur Acad Dermatol Venereol 17: 251-256.
- Rundshagen U et al (2003) Mutations in the MATP gene in five German patients affected by oculocutaneous albinism type 4. Hum Mutat 23: 106-110.
- Terenziani M et al (2003) Amelanotic melanoma in a child with oculocutaneous albinism. Med Pediatr Oncol 41: 179-180
Incoming links (8)Albinismus, oculocutaneous type 7; Basal cell carcinomatosis; Chromosome 9; Griscelli syndrome; LRMDA Gene; Oca; OCA3; Oculocutaneous albinism;
Outgoing links (15)Albinism, oculocutaneous, brown; Albinism oculocutaneous tyrosinase-negative; Albinism oculocutaneous tyrosinase-positive; Albinism, oculocutaneous, yellow mutant; Albinismus, oculocutaneous type 7; Albinismus okulocutaneous type 5; Chediak higashi syndrome; Griscelli syndrome; Hermansky-pudlak syndrome; LRMDA Gene; ... Show all
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