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Clinical Ophthalmology (Auckland, N.Z.) 2022Albinism describes a heterogeneous group of genetically determined disorders characterized by disrupted synthesis of melanin and a range of developmental ocular... (Review)
Review
Albinism describes a heterogeneous group of genetically determined disorders characterized by disrupted synthesis of melanin and a range of developmental ocular abnormalities. The main ocular features common to both oculocutaneous albinism (OCA), and ocular albinism (OA) include reduced visual acuity, refractive errors, foveal hypoplasia, congenital nystagmus, iris and fundus hypopigmentation and visual pathway misrouting, but clinical signs vary and there is phenotypic overlap with other pathologies. This study reviews the prevalence, genetics and ocular manifestations of OCA and OA, including abnormal development of the optic chiasm. The role of visual electrophysiology in the detection of chiasmal dysfunction and visual pathway misrouting is emphasized, highlighting how age-associated changes in visual evoked potential (VEP) test results must be considered to enable accurate diagnosis, and illustrated further by the inclusion of novel VEP data in genetically confirmed cases. Differential diagnosis is considered in the context of suspected retinal and other disorders, including rare syndromes that may masquerade as albinism.
PubMed: 35637898
DOI: 10.2147/OPTH.S329282 -
Orphanet Journal of Rare Diseases Nov 2007Oculocutaneous albinism (OCA) is a group of inherited disorders of melanin biosynthesis characterized by a generalized reduction in pigmentation of hair, skin and eyes.... (Review)
Review
Oculocutaneous albinism (OCA) is a group of inherited disorders of melanin biosynthesis characterized by a generalized reduction in pigmentation of hair, skin and eyes. The prevalence of all forms of albinism varies considerably worldwide and has been estimated at approximately 1/17,000, suggesting that about 1 in 70 people carry a gene for OCA. The clinical spectrum of OCA ranges, with OCA1A being the most severe type with a complete lack of melanin production throughout life, while the milder forms OCA1B, OCA2, OCA3 and OCA4 show some pigment accumulation over time. Clinical manifestations include various degrees of congenital nystagmus, iris hypopigmentation and translucency, reduced pigmentation of the retinal pigment epithelium, foveal hypoplasia, reduced visual acuity usually (20/60 to 20/400) and refractive errors, color vision impairment and prominent photophobia. Misrouting of the optic nerves is a characteristic finding, resulting in strabismus and reduced stereoscopic vision. The degree of skin and hair hypopigmentation varies with the type of OCA. The incidence of skin cancer may be increased. All four types of OCA are inherited as autosomal recessive disorders. At least four genes are responsible for the different types of the disease (TYR, OCA2, TYRP1 and MATP). Diagnosis is based on clinical findings of hypopigmentation of the skin and hair, in addition to the characteristic ocular symptoms. Due to the clinical overlap between the OCA forms, molecular diagnosis is necessary to establish the gene defect and OCA subtype. Molecular genetic testing of TYR and OCA2 is available on a clinical basis, while, at present, analysis of TYRP1 and MATP is on research basis only. Differential diagnosis includes ocular albinism, Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, Griscelli syndrome, and Waardenburg syndrome type II. Carrier detection and prenatal diagnosis are possible when the disease causing mutations have been identified in the family. Glasses (possibly bifocals) and dark glasses or photocromic lenses may offer sufficient help for reduced visual activity and photophobia. Correction of strabismus and nystagmus is necessary and sunscreens are recommended. Regular skin checks for early detection of skin cancer should be offered. Persons with OCA have normal lifespan, development, intelligence and fertility.
Topics: Albinism, Oculocutaneous; Diagnosis, Differential; Humans; Prevalence
PubMed: 17980020
DOI: 10.1186/1750-1172-2-43 -
Der Hautarzt; Zeitschrift Fur... Nov 2017Albinism can be divided into oculocutaneous albinism (OCA) and ocular albinism (OA). In the differential diagnostics these can be distinguished from rarer syndromes with... (Review)
Review
Albinism can be divided into oculocutaneous albinism (OCA) and ocular albinism (OA). In the differential diagnostics these can be distinguished from rarer syndromes with partial albinism, which are frequently associated with susceptibility to infections and neurological symptoms. The OCA is an autosomal recessive inherited disease of melanin biosynthesis, which leads to complete or partial loss of melanin in the skin, hair follicles and eyes. Of the seven currently known subtypes (OCA 1-7), four are well-characterized (OCA 1-4). These are based on gene mutations, which code for tyrosinase, a key enzyme in melanin synthesis and for further proteins. These play an important role in the catalytic activity of tyrosinase and the structure and function of melanosomes. In the presence of these subtypes, the clinical symptoms and the course of the disease show a pronounced variability, especially in the type and extent of pigmentation of the skin and hair as well as the severity of eye involvement, which makes the phenotypic classification difficult. Treatment priorities are a consistent protection from UV light for prophylaxis against skin cancer and regular preventive investigations. The ocular alterations typical for albinism necessitate timely diagnostics and care by institutions specialized in ophthalmology. Novel strategies for systemic treatment of subtypes of albinism are in preclinical testing. The OA without skin involvement shows X‑linked inheritance, is much rarer and is characterized by reduced pigmentation of the retina and iris, nystagmus and macular hypoplasia, sometimes with substantial loss of visual acuity. The typical ocular symptoms of OA can be manifested to a varying extent in all forms of OCA.
Topics: Albinism, Ocular; Albinism, Oculocutaneous; Chromosome Aberrations; DNA Mutational Analysis; Diagnosis, Differential; Early Diagnosis; Early Medical Intervention; Genes, Recessive; Genes, X-Linked; Humans; Interdisciplinary Communication; Intersectoral Collaboration; Melanins; Monophenol Monooxygenase
PubMed: 29018889
DOI: 10.1007/s00105-017-4061-x -
Progress in Retinal and Eye Research Nov 2022Albinism is a pigment disorder affecting eye, skin and/or hair. Patients usually have decreased melanin in affected tissues and suffer from severe visual abnormalities,... (Review)
Review
Albinism is a pigment disorder affecting eye, skin and/or hair. Patients usually have decreased melanin in affected tissues and suffer from severe visual abnormalities, including foveal hypoplasia and chiasmal misrouting. Combining our data with those of the literature, we propose a single functional genetic retinal signalling pathway that includes all 22 currently known human albinism disease genes. We hypothesise that defects affecting the genesis or function of different intra-cellular organelles, including melanosomes, cause syndromic forms of albinism (Hermansky-Pudlak (HPS) and Chediak-Higashi syndrome (CHS)). We put forward that specific melanosome impairments cause different forms of oculocutaneous albinism (OCA1-8). Further, we incorporate GPR143 that has been implicated in ocular albinism (OA1), characterised by a phenotype limited to the eye. Finally, we include the SLC38A8-associated disorder FHONDA that causes an even more restricted "albinism-related" ocular phenotype with foveal hypoplasia and chiasmal misrouting but without pigmentation defects. We propose the following retinal pigmentation pathway, with increasingly specific genetic and cellular defects causing an increasingly specific ocular phenotype: (HPS1-11/CHS: syndromic forms of albinism)-(OCA1-8: OCA)-(GPR143: OA1)-(SLC38A8: FHONDA). Beyond disease genes involvement, we also evaluate a range of (candidate) regulatory and signalling mechanisms affecting the activity of the pathway in retinal development, retinal pigmentation and albinism. We further suggest that the proposed pigmentation pathway is also involved in other retinal disorders, such as age-related macular degeneration. The hypotheses put forward in this report provide a framework for further systematic studies in albinism and melanin pigmentation disorders.
Topics: Humans; Melanins; Mutation; Albinism; Retina; Pigmentation
PubMed: 35729001
DOI: 10.1016/j.preteyeres.2022.101091 -
Advances in Experimental Medicine and... 2018The prevalence of X-linked ocular albinism (XLOA) is about 1 in 60,000 males. It affects only the eyes; the color of the skin and hairs are normal. Patients usually...
The prevalence of X-linked ocular albinism (XLOA) is about 1 in 60,000 males. It affects only the eyes; the color of the skin and hairs are normal. Patients usually present with reduced vision, photophobia, nystagmus, and strabismus. Many patients have problem in perceiving depth (stereoscopic vision). The visual loss is permanent, but XLOA is a nonprogressive disorder and visual acuity remains stable throughout life.
Topics: Albinism, Ocular; Depth Perception; Genetic Diseases, X-Linked; Humans; Male; Nystagmus, Pathologic; Photophobia; Strabismus
PubMed: 30578484
DOI: 10.1007/978-3-319-95046-4_11 -
Canadian Journal of Ophthalmology.... Dec 2019
Topics: Albinism, Ocular; Canada; Chromosome Mapping; Chromosomes, Human, X; Cloning, Molecular; Genetic Diseases, X-Linked; History, 19th Century; History, 20th Century; Humans
PubMed: 31836092
DOI: 10.1016/j.jcjo.2019.05.014 -
Archives of Ophthalmology (Chicago,... Jan 1988
Topics: Albinism; Child, Preschool; Fluorescein Angiography; Fundus Oculi; Humans; Iris; Male; Ophthalmoscopy; Transillumination
PubMed: 3337686
DOI: 10.1001/archopht.1988.01060130126042