TYR mutation in a Chinese population with oculocutaneous albinism: Molecular characteristics and ophthalmic manifestations.

Oculocutaneous albinism (OCA) is a rare inherited disorder characterized by a partial or complete reduction of melanin biosynthesis that leads to hypopigmentation in the skin, hair and eyes. The OCA1 subtype is caused by mutations in TYR. The purpose of this study was to investigate the genetic and clinical ophthalmic characteristics of TYR mutations in patients with OCA. Herein, 51 probands with a clinical diagnosis of OCA were enrolled. Whole-exome sequencing and comprehensive ophthalmic examinations were performed. Overall, TYR mutations were detected in 37.3% (19/51) in the patients with OCA. Fifteen patients had compound heterozygous variants, and four cases had homozygous variants. Eleven different pathogenic variants in TYR were detected in these 19 patients, with missense, insertion, delins and nonsense in 71.1% (27/38), 15.8% (6/38), 2.6% (1/38), and 10.5% (4/38), respectively. Clinical examinations revealed that 84.2% (16/19) of patients were OCA1A, and 15.8% (3/19) were OCA1B. Most TYR probands (52.6%, 10/19) had moderate vision impairment, 15.8% (3/19) had severe visual impairment, 10.5% (2/19) exhibited blindness, only 5.3% (1/19) had mild visual impairment and 15.8% (3/19) were not available. Photophobia and nystagmus were found in 100% (19/19) of the patients. In addition, grade 4 foveal hypoplasia was detected in 100% (12/12) of the patients. In conclusion: The TYR patients exhibited severe ocular phenotypes: the majority (93.8%, 15/16) of them had a moderate vision impairment or worse, and 100% (12/12) had severe grade 4 foveal hypoplasia. These novel findings could provide insight into the understanding of OCA.

Children with albinism in African regions: their rights to 'being' and 'doing'.

BACKGROUND: Albinism is an inherited condition with a relatively high prevalence in populations throughout sub-Saharan Africa. People with oculocutaneous albinism have little or no pigment in their hair, skin and eyes; thus they are visually impaired and extremely sensitive to the damaging effect of the sun on their skin. Aside from the health implications of oculocutaneous albinism, there are also significant sociocultural risks. The impacts of albinism are particularly serious in areas that associate albinism with legend and folklore, leading to stigmatisation and discrimination. In regions of Africa those with albinism may be assaulted and sometimes killed for their body parts for use in witchcraft-related rites or to make 'lucky' charms. There is a dearth of research on the psychosocial aspects of albinism and particularly on how albinism impacts on the everyday lives of people with albinism. DISCUSSION: There is a growing recognition and acceptance in Africa that people with albinism should be considered disabled. Thomas's social-relational model of disability proposes it is essential to understand both the socio-structural barriers and restrictions that exclude disabled people (barriers to doing); and the social processes and practices which can negatively affect their psycho-emotional wellbeing (barriers to being). In this article, we combine a social model of disability with discussion on human rights to address the lacuna surrounding the psychosocial and daily experiences of people with albinism. CONCLUSION: Through using this combined framework we conclude that the rights of people with albinism in some regions of Africa are not being enacted. Our debate highlights the need to develop a holistic concept of rights for children and young people with albinism which sees human rights as indivisible. We illuminate some of the specific ways in which the lives of children with albinism could be improved by addressing 'barriers to being' and 'barriers to doing', at the heart of which requires a shift in attitude and action to address discrimination.

Association study confirms the role of two OCA2 polymorphisms in normal skin pigmentation variation in East Asian populations.

OBJECTIVES: The main goal of the study was to test the association of 18 polymorphisms located within nine pigmentation candidate genes with quantitative skin pigmentation measures collected in a sample of individuals of East Asian ancestry living in Canada (N = 419). METHODS: The 18 polymorphisms are located within genes that show putative signatures of positive selection in East Asian populations. The genetic markers were selected for genotyping based on an annotation of common East Asian polymorphisms to predict potential functional effects. We restricted our attention to polymorphisms that have an allele frequency difference of at least 30% between East Asian populations and African and European populations, or have alleles that are present in East Asians, but are absent in Africans and Europeans. RESULTS: Two nonsynonymous variants selected within the OCA2 gene, rs1800414 (His615Arg) and rs74653330 (Ala481Thr), were significantly associated with melanin levels in the sample. Both single nucleotide polymorphisms (SNPs) are nonsynonymous polymorphisms located more than 30 kb apart on chromosome 15 and have very different frequencies in the East Asian sample. Additionally, both polymorphisms are predicted to have a deleterious effect on the protein. Linear regression analysis using an additive model indicate that each copy of the derived rs1800414 allele G decreases Melanin Index approximately 0.9 units and each copy of the derived rs74653330 allele A decreases Melanin Index approximately 1.9 units. CONCLUSIONS: Two nonsynonymous OCA2 polymorphisms (rs1800414 and rs74653330) are independently associated with normal skin pigmentation variation in East Asian populations and have very different frequency distributions in East Asia.

Prevalence and profile of ophthalmic disorders in oculocutaneous albinism: a field report from South-Eastern Nigeria.

To assess the burden and spectrum of refractive and non-refractive ophthalmic disorders in south-eastern Nigerians with oculocutaneous albinism. In a population-based survey in Enugu state, between August, 2011 and January, 2012, albinos were identified using the database of the Enugu state's Albino Foundation, and mass media-based mobilisation. The participants were enrolled at the Eye Clinics of the University of Nigeria Teaching Hospital and Enugu State University of Science and Technology Teaching Hospital using a defined protocol. Relevant socio-demographic and clinical data were obtained from each participant. Descriptive and comparative statistics were performed. Statistical significance was indicated by p < 0.05. The participants (n = 153; males, 70) were aged 23.5 + 10.4 SD years (range 6-60 years). Both refractive and non-refractive disorders were present in all participants. Non-refractive disorders comprised nystagmus, foveal hypoplasia, hypopigmented fundi and prominent choroidal vessels in 100.0% participants; and strabismus in 16.3% participants. Refractive disorders comprised astigmatism -73.2% eyes, myopia -23.9% and hypermetropia 2.9%. Spherical refractive errors ranged from -14.00 DS to +8.00 DS while astigmatic errors ranged from -6.00 DC to +6 DC. Mixed refractive and non-refractive disorder i.e. presenting visual impairment was present in 100.0% participants. Overall, refractive error was associated with non-possession of tertiary education (OR 0.61; 95% CI 0.38-0.96; p = 0.0374). There is high prevalence of refractive, non-refractive and mixed ophthalmic disorders among albinos in south-eastern Nigeria. This underscores the need for tailored provision of resources to address their eye care needs, and creation of needs awareness amongst them.

DNA variations in oculocutaneous albinism: an updated mutation list and current outstanding issues in molecular diagnostics.

Oculocutaneous albinism (OCA) is a rare genetic disorder of melanin synthesis that results in hypopigmented hair, skin, and eyes. There are four types of OCA caused by mutations in TYR (OCA-1), OCA2 (OCA-2), TYRP1 (OCA-3), or SLC45A2 (OCA-4). Here we report 22 novel mutations in the OCA genes; 14 from a cohort of 61 patients seen as part of the NIH OCA Natural History Study and eight from a prior study at the University of Minnesota. We also include a comprehensive list of almost 600 previously reported OCA mutations along with ethnicity information, carrier frequencies, and in silico pathogenicity predictions as a supplement. In addition to discussing the clinical and molecular features of OCA, we address the cases of apparent missing heritability. In our cohort, 26% of patients did not have two mutations in a single OCA gene. We demonstrate the utility of multiple detection methods to reveal mutations missed by Sanger sequencing. Finally, we review the TYR p.R402Q temperature-sensitive variant and confirm its association with cases of albinism with only one identifiable TYR mutation.

Positional cloning of a gene for Hermansky-Pudlak syndrome, a disorder of cytoplasmic organelles.

Hermansky-Pudlak syndrome (HPS) is an often-fatal autosomal recessive disease in which albinism, bleeding, and lysosomal storage result from defects of diverse cytoplasmic organelles: melanosomes, platelet dense bodies, and lysosomes. HPS is the most common single-gene disorder in Puerto Rico, with an incidence of 1 in 1,800. We have identified the HPS gene by positional cloning, and found homozygous frameshifts in this gene in Puerto Rican, Swiss, Irish and Japanese HPS patients. The HPS polypeptide is a novel transmembrane protein that is likely to be a component of multiple cytoplasmic organelles and that is apparently crucial for their normal development and function. The different clinical phenotypes associated with the different HPS frameshifts we observed suggests that differentially truncated HPS polypeptides may have somewhat different consequences for subcellular function.

Determining a Worldwide Prevalence of Oculocutaneous Albinism: A Systematic Review.

Purpose: The aim of this systematic review was to investigate the available data on the epidemiology of oculocutaneous albinism (OCA) around the world, and to determine whether a generalizable, worldwide prevalence figure could be proposed. Methods: Extensive literature search strategies were conducted, interrogating PubMed, Scopus, and Web of Science, to locate relevant literature. Ultimately 34 studies reporting original data were included for analysis. Results: Findings showed that most data were outdated, and only 6 of 34 articles (18%) were published after 2010. There were few good studies with sound methodology and large, clearly defined population samples. Only a small proportion of countries worldwide (26/193 [13%]) have produced prevalence figures for OCA. By continent, African studies were disproportionately represented (15/34 [44%]). The highest prevalence rates (range, 1 in 22 to 1 in 1300; mean, 1 in 464) were reported in population isolates. The mean prevalence from four African countries was 1 in 4264 (range, 1 in 1755 to 1 in 7900). Prevalence for three countries in Europe (mean, 1 in 12,000; range, 1 in 10,000 to 1 in 15,000) may be underestimated, as the phenotype, in fair-skinned populations, may be missed or misdiagnosed as ocular albinism or isolated visual impairment. Population rates may vary depending on local cultural factors (e.g., consanguineous matings) and may change over time. Conclusions: The prevalence of OCA varies widely between continents and population groups, and it is often influenced by local factors. It was not possible, therefore, to determine a single, generalizable worldwide prevalence rate for OCA, although continental rates for Africa and Europe are useful.

Oculocutaneous albinism: epidemiology, genetics, skin manifestation, and psychosocial issues.

Oculocutaneous albinism (OCA) is a group of rare, inherited disorders associated with reduced melanin biosynthesis. Clinical manifestations of the eight known subtypes of OCA include hypopigmented skin, eyes, and hair and ocular manifestations, such as decreased visual acuity and nystagmus. OCA affects people globally but is most prevalent in African countries. Individuals with oculocutaneous albinism lack UV protection and are prone to skin damage and skin cancers. For many African albino individuals, there are significant challenges in seeking treatment for skin cancer and preventing sun damage due to psychosocial factors and poor education. This review summarizes the current understanding of the epidemiology, genetics, and clinical manifestations of OCA. We also discuss the medical and psychosocial challenges that affect individuals with OCA and the current landscape of albinism treatment modalities. The extent of the psychosocial challenges needs to be better understood and additional educational interventions may improve quality of life for people with albinism.

Photosensitivity and filter efficacy in albinism✰.

PURPOSE: To describe the prevalence and severity of photosensitivity in patients with albinism, and to compare with ocular features and how this correlated with use and choice of optical filters. METHODS: Cross-sectional study on 81 participants with ocular or oculocutaneous albinism. An ophthalmic evaluation including visual acuity, contrast sensitivity and evaluation of iris translucency and fundus hypopigmentation was performed. Participants were offered optical rehabilitation with testing of a wide panel of filters. The associations between ocular characteristics, subjective photosensitivity complaints, and filter choice were evaluated. RESULTS: Photosensitivity was rated as "some" to "worst imaginable" in 77.8% of participants. Severity of photosensitivity correlated significantly with fundus hypopigmentation (p = 0.04) but not with iris translucency (p = 0.14) and it was worse in those with poor visual acuity but there was no association between photosensitivity and contrast vision. Seventy-four new pairs of spectacles were prescribed in the study. All outdoor spectacles contained a filter, whereas 26.5% of new indoor spectacles did not. Relatively neutral filter colors (gray, brown or a combination of gray and brown with other colors) and low transmission were preferred. DISCUSSION: Photosensitivity is common in albinism, but research targeting treatment is limited. Color and neutral filters with a low light transmission were preferred, with participants having a large number of spectacles, presumably to meet their needs in different situations.

[A case for the inclusion of oculocutaneous albinism as a skin-related Neglected Tropical Disease]. / Plaidoyer pour une intégration de l'albinisme oculocutané au sein des Maladies tropicales négligées dermatologiques.

Oculocutaneous albinism (OCA) is genetically transmitted. In this paper we advocate for this disease to be included in the NTD list of the WHO. OCA type 2 is the most common form of albinism in sub-Saharan Africa, with a prevalence of 1 in 7900 among the Bamileke of Cameroon, 1 in 3900 in South Africa and 1 in 1100 among the Ibos of Nigeria, as compared to a prevalence of 1 in 10,000 among African Americans and 1 in 36,000 among White Americans and Europeans. The medical problems related to ophthalmological aspects (poor visual acuity, ametropia, nystagmus, photophobia) and dermatological aspects of albinism (sensitivity to UV rays from the sun and development of skin cancers) are well known. However, their management is often challenging for persons with albinism in sub-Saharan Africa because of their financial burden and the difficulty of accessing medical specialists. In many African countries, persons with albinism are also very often the subject of social, cultural, medical, moral and economic discrimination, which can limit their access to education, employment and community life. They are considered 'white Africans', intermediary and incomplete, with innate powers for good and evil. This particularity has made persons with albinism the targets of mutilations and/or ritual attacks for the purposes of using their body parts in the preparation of charms to bring good luck, health or prosperity. On 13 June 2013, as a result of lobbying by the Canadian NGO Under the Same Sun and African albinism associations, United Nations bodies including UNESCO and the WHO (World Health Organization) responded and a Resolution addressing the discrimination and attacks was voted in. The date has since become International Albinism Awareness Day and is celebrated on a different theme each year with great energy and impact, especially by French, English and Portuguese speaking albinism associations across sub-Saharan Africa. In 2015 the Human Rights Council created the position of Independent Expert on Albinism to better collect and analyse data on the rights of persons with albinism around the world, and especially in countries where ritual attacks occur. The data collected by albinism associations and the authorities thus go directly to the UN Human Rights Directorate. Despite this international attention to the attacks on persons with albinism, one of the biggest threats is skin cancer, which very often leads to early death. In 2022, the WHO launched a strategic framework for the control and management of neglected skin-related neglected tropical diseases - an additional reason to include oculocutaneous albinism as an NTD. Although the focus is currently limited to dermatoses of an infectious nature, we argue here for the integration of oculocutaneous albinism among NTDs because the deadliness of these carcinomas in sub-Saharan Africa is well-known and has been examined in a number of medical publications. Here, we propose that oculocutaneous albinism in sub-Saharan Africa be classified as an NTD to help people with albinism have access to health, economic, social and cultural rights.

The prevalence of nonmelanoma skin cancer in a population of patients with oculocutaneous albinism in Haiti.

BACKGROUND: Multiple studies have examined the prevalence of nonmelanoma skin cancers (NMSC) in patients with oculocutaneous albinism (OCA). However, to date, no studies have examined this data in Caribbean populations. METHODS: This study is a cross-sectional study of 106 patients with OCA who were seen at the Oculocutaneous Albinism Clinic in Port-au-Prince and Gros Morne, Haiti, between the dates of February 2017 and June 2018. RESULTS: In our population, 31/106 (29%) patients were found to have NMSC, 10/31 (32%) had BCC, 12/31 (39%) had SCC, and 9/31 (29%) had both types of NMSC. The most common age groups were 31-40 years, with the overall range of ages being 18-63 years. Also, 60/106 (57%) of the patients had actinic keratoses (AK). CONCLUSIONS: Our study provides new data examining the prevalence of NMSC within a population of patients with OCA in Haiti. Overall, it shows that patients with albinism develop NMSC at an earlier age compared with the rest of the population. Therefore, appropriate skin cancer screening and surveillance should be implemented within this high-risk population group.

Current landscape of Oculocutaneous Albinism in Japan.

Oculocutaneous albinism (OCA), which is roughly divided into non-syndromic and syndromic OCA, is a group of autosomal recessive disorders caused by mutations in genes associated with pigmentation. Patients with OCA have hypopigmentation and ocular manifestations such as photophobia, amblyopia, and nystagmus. Hermansky-Pudlak syndrome (HPS), the most common syndromic OCA, is characterized by the additional features of a bleeding tendency and other critical systemic comorbidities such as pulmonary fibrosis and immunodeficiency. NGS-based gene analyses have identified several new causative genes for OCA and have detected rare subtypes of OCA with high accuracy including Japanese patients. In our survey of 190 Japanese OCA patients/families, OCA4 is the most common subtype (25.3%) followed by OCA1 (20.0%), HPS1 (14.7%), and OCA2 (8.4%). Similar to the A481T variant in OCA2, which is associated with a mild form of OCA2 and skin color variation, the c.-492_489delAATG variant located in the promoter region of SLC45A2 has been uniquely identified in Japanese patients with a mild form of OCA4. Further, rare OCA subtypes, including OCA3, HPS2, HPS3, HPS4, HPS5, HPS6, and HPS9, have also been identified in Japanese patients. The clinical characteristics and underlying molecular mechanisms of each subtype of OCA are concisely summarized in this review.

Prevalence of premalignant and malignant skin lesions in oculocutaneous albinism patients.

OBJECTIVE: Oculocutaneous albinism describes a group of pigmentary disorders that lead to skin sensitivity and predisposition to skin malignances. AIMS: To analyze clinical and epidemiological data in oculocutaneous albinism patients and to determine the prevalence of malignant skin lesions, assessing possible risk factors for skin cancer. METHODS: Cross-sectional study evaluating epidemiological data, habits of sun exposure and sun protection, and clinical examination of albino patients followed in a reference dermatology outpatient clinic in Brasil. Our primary outcome was the occurrence of malignant skin lesions in biopsied tissues. RESULTS: Of 74 patients analyzed, 11 (15%) had one or more suspicious lesions and were biopsied, of which 8 (72.7%) patients presented with basal cell carcinomas, 7 (63.3%) presented with squamous cell carcinoma, and 1 (9%) presented with melanoma. Moreover, 32(43%) patients presented with actinic keratosis. Age, female gender, previous history of sunburn, history of malignant lesions and history of sun exposure without photoprotection were associated with the presence of malignant lesions. LIMITATIONS: Unicentric, non-aleatory sample. CONCLUSIONS: There was a high prevalence of malignant and pre-malignant lesions in this population. Some potentially modifiable risk factors were associated with the occurrence of malignant skin lesions.

Evident hypopigmentation without other ocular deficits in Dutch patients with oculocutaneous albinism type 4.

To describe the phenotype of Dutch patients with oculocutaneous albinism type 4 (OCA4), we collected data on pigmentation (skin, hair, and eyes), visual acuity (VA), nystagmus, foveal hypoplasia, chiasmal misrouting, and molecular analyses of nine Dutch OCA4 patients from the Bartiméus Diagnostic Center for complex visual disorders. All patients had severely reduced pigmentation of skin, hair, and eyes with iris transillumination over 360 degrees. Three unrelated OCA4 patients had normal VA, no nystagmus, no foveal hypoplasia, and no misrouting of the visual pathways. Six patients had poor visual acuity (0.6 to 1.0 logMAR), nystagmus, severe foveal hypoplasia and misrouting. We found two novel variants in the SLC45A2 gene, c.310C > T; (p.Pro104Ser), and c.1368 + 3_1368 + 9del; (p.?). OCA4 patients of this Dutch cohort all had hypopigmentation of skin, hair, and iris translucency. However, patients were either severely affected with regard to visual acuity, foveal hypoplasia, and misrouting, or visually not affected at all. We describe for the first time OCA4 patients with an evident lack of pigmentation, but normal visual acuity, normal foveal development and absence of misrouting. This implies that absence of melanin does not invariably lead to foveal hypoplasia and abnormal routing of the visual pathways.

Inheritance of a novel mutated allele of the OCA2 gene associated with high incidence of oculocutaneous albinism in a Polynesian community.

Oculocutaneous albinism type 2 (OCA2) is a human autosomal-recessive hypopigmentation disorder associated with pathological mutations of the OCA2 gene. In this study, we investigated a form of OCA in a Polynesian population with an observed phenotype characterized by fair skin, some brown nevi present in the sun-exposed areas and green or blue eyes. Hair presented with a unique red coloration since birth, with tones ranging across individuals from Yellow-Red to Brown-Red, or Auburn. We genetically screened for mutations in the OCA2 and MC1R genes as their products have previously been shown to be associated with red hair/fair skin and OCA2. The SLC45A2 gene was also screened to identify any possible relation to skin color variation. We have identified a novel missense substitution in the OCA2 gene (Gly775Asp) responsible for OCA2 in individuals of Polynesian heritage from Tuvalu. The estimated incidence of this form of OCA2 in the primary study community is believed to occur at one of the highest recorded rates of albinism at approximately 1 per 669 individuals. In addition, we have analyzed four unrelated individuals with albinism who have Polynesian heritage from three other separate communities and found they carry the same OCA2 mutation. We also analyzed an out-group comprising three unrelated individuals with albinism of Melanesian ancestries from two separate communities, one Australian Aboriginal and three Australian Caucasians, and did not detect this mutation. We hypothesize that this mutation may be Polynesian specific and that it originated from a common founder.

Albinism and its implications with vision.

Albinism is an inherited disorder characterized by a reduction or absence of melanin in the hair, skin, and/or eyes. Tyrosinase, a major enzyme required in the production of melanin, is deficient to varying degrees in albinism. Albinism can be divided into one of two broad categories, oculocutaneous and ocular albinism, based on the involvement of hair, skin and the eyes versus only the eyes, respectively. Common ocular findings include reduced visual acuity, refractive errors, iris transillumination, nystagmus, foveal hypoplasia, fundus hypopigmentation and misrouting of optic nerve fibres at the chiasm. Eye care professionals can play an important role when tending to patients with albinism. This article will provide the reader with an overview of the etiology of albinism, the prevalence, clinical manifestations and management options.

Recent advances in genetic analyses of oculocutaneous albinism types 2 and 4.

Patients with OCA are characterized by reduced skin and hair pigmentation and consequent photosensitivity, actinic damage and risk of skin cancer, and by reduced visual acuity and nystagmus. Our survey of Japanese patients revealed that OCA1 was the most frequent type at 34%, while type 2 was present at less than 10%. OCA3 was absent. OCA4, which is a rare type worldwide, was the second most frequent type at 27%. Unexpectedly 10% of the patients turned out to be Hermansky-Pudlak syndrome type 1. Furthermore, the pathogenic p.A481T allele for OCA2, which has 70% melanogenesis activity, was found in approximately 12% of normally pigmented people, indicating that sub-clinical OCA2 might be more frequent in the Japanese than currently thought. And OCA4 is one of the most common types in Japanese patients, despite being rare worldwide.

Oculocutaneous albinism type 1A: a case report.

The term, oculocutaneous albinism (OCA), describes a group of inherited disorders of melanin biosynthesis that exhibits congenital hypopigmentation of ocular and cutaneous tissues. The clinical spectrum of OCA ranges from a complete lack of melanin pigmentation to mildly hypopigmented forms. OCA1A is the most severe type with a complete lack of melanin production throughout life; 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 and refractive errors, color vision impairment, and prominent photophobia. 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. Herein we present a case with OCA1A.

GABA(A) receptor alpha5 subunit as a candidate gene for autism and bipolar disorder: a proposed endophenotype with parent-of-origin and gain-of-function features,with or without oculocutaneous albinism.

Our earlier family history studies of individuals with autism found a high incidence of major affective disorder, especially bipolar disorder, and unusual talents or intellectual abilities among family members. We now describe a subgroup of such families, selected from a large clinical experience, illustrating specific features of major affective disorder, special talents or intellectual ability, and familial patterns of trait transmission, with the additional feature of oculocutaneous albinism in some cases. These observations, suggesting parent-of-origin and gain-of-function effects, considered together with recent genetic findings in the literature, suggest a genetic hypothesis possibly unifying disparate observations found in families of individuals with autism.