Subtypes Of Oculocutaneous Albinism Research Articles

Identifying genetic defects in oculocutaneous albinism patients of West Bengal, Eastern India.

Oculocutaneous albinism (OCA) is a congenital heterogeneous group of autosomal recessive disorders characterized by the absence or loss of melanin in the skin, eyes and hair of the affected individuals. Based on the mutated gene, OCA has been classified into eight sub-types (OCA1-8) with overlapping clinical phenotypes. Mutations in the TYR gene cause OCA1, the most prevalent OCA worldwide including India. Mutations in OCA2 and SLC45A2, both of which regulate melanosomal pH that is critical to TYR activity, cause OCA2 and OCA4 respectively, the other common OCA subtypes in India. In the present study, we have included 54 OCA-affected cases from 41 unrelated families representing 16 different marriage/ethnic groups from 17 districts of West Bengal, India. We pursued a PCR-sequencing based approach followed by bioinformatic analysis to identify mutations in TYR, OCA2 and SLC45A2 genes. Mutations were detected in 27 of the 54 (50%) OCA patients from 18 unrelated families, representing 9 different marriage/ethnic groups from 11 districts of West Bengal. Three TYR variants: NM_000372.4: c.391 A > G, NP_000363.1: p. Lys131Glu; NM_000372.4: c.1037G > T; NP_000363.1: p. Gly346Val, NM_000372.4: c.715 C > T; NP_000363.1:p.Arg239Trp was identified for the first time in Eastern Indian OCA cases. A novel nonsense variant: NM_016180.5: c.389T > A, NP_057264.4: p. Leu130* and a novel synonymous variation NM_016180.5: c.1092 A > G; NP_057264.4: p.364E = were identified in SLC45A2. Additionally, NM_016180.5: c.904A > T; NP_057264.4: p. Thre302Ser was identified for the first time in any Eastern Indian OCA case. We identified 2 previously reported mutations in OCA2. In concordance with previous reports, NM_000372.4: c.832C > T, NP_000363.1: p. (Arg278*) was the commonest TYR mutation. The results of our study enrich the mutational spectrum of the known OCA causing genes in Eastern India, which would facilitate accurate diagnosis, familial screening, carrier detection and containment of the disease load.

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.

Pediatric patient with oculocutaneous albinism

Oculocutaneous albinism (OCA) is a heterogeneous autosomal recessive disorder characterized by a reduced or absent melanin synthesis. OCA causes a complete or partial absence of pigment in the skin, hair, and eyes. Reduction of melanin in the eyes results in reduced visual acuity, photophobia, and nystagmus. A 6-year-old boy, the first child of a related couple, was born following a normal gestation and delivery. At term, he weighed 3800 g, and his length was 50 cm. OCA was noted at birth; there was total depigmentation of the skin, hair, and iris. He presented with photophobia and bilateral strabismus. The patient had white hair, eyebrows, eyelashes, and depigmented skin (A). Ophthalmologic examination revealed characteristic iris depigmentation and translucency (B), retinal depigmentation (C), misrouting of the optic nerve fibers and reduced visual acuity (5/10). He had a normal mental development with no other congenital deformities. He did not have any abnormalities of the internal organs. The diagnosis of OCA is based on clinical findings of hypopigmentation of the skin and hair, in addition to the characteristic ocular symptoms. However, due to the clinical overlap between the OCA subtypes, molecular diagnosis is necessary in order to establish the gene defect and thus the OCA subtype. Reduced visual acuity can be helped in various ways. Glasses, possibly bifocals, may often be of sufficient help. Oculocutaneous albinism is an autosomal recessive disorder that presents with heterogeneous expressivity.

A Superpower Tree Mapping and Tracing (STMT) Algorithm for OCA Sub-types Classification and Associated Risk Factors Identification

Medical data mining supports the experts for early prediction of diseases and identifying subtypes of disease is important for prognosis, management and recommended remedy. Here we imply data mining technology for the classification of various types of oculocutaneous albinism (OCA) and its severity. We introduce a new superpower tree mapping and tracing (STMT) classification algorithm which predicts the sub type of OCA using tree tracing method in every direction. Easy Linkage software is used to find out feature linkages. STMT involves in computing the sub tree DOCSCORE which is used to classify the concern OCA-type. According to the OCA type, our Stop Watch Go model determines the severity of the disease using confidential and credential limitation values. This approach recommends the required prevention to increase the lifespan of the patient. We evaluated our algorithm with 200 OCA clinical data records collected from central hospital, Chennai and classified the types of OCA with the selected features. We used external features like hypopigmentation of hair, skin, eye color and clinical features such as nystagmus, strabismus, photophobia, poor vision and impacts of disease. The classification accuracy of proposed STMT algorithm shows that 4% more effective than traditional classifier algorithms such as KNN classifier and Naive Bayesian classifier. A comparative study is also implemented with other existing works to check the superiority of the proposed method. Hence, it is revealed from the results of the classification algorithm that the proposed method can be used as a supplementary tool for the experts to diagnose the subtypes of oculocutaneous albinism and simplify the analysis of various physiological signals of patients.

Genetic analysis and prenatal diagnosis of 20 Chinese families with oculocutaneous albinism.

BackgroundOculocutaneous albinism (OCA) is a group of heterogeneous genetic disorders characterized by abnormal melanin synthesis in the hair, skin, and eyes. OCA exhibits obvious genetic and phenotypic heterogeneity. Molecular diagnosis of causal genes can be of help in the classification of OCA subtypes and the study of OCA pathogenesis．MethodsIn this study, Sanger sequencing and whole exome sequencing were used to genetically diagnose 20 nonconsanguineous Chinese OCA patients. In addition, prenatal diagnosis was provided to six OCA families.ResultsVariants of TYR, OCA2, and HPS1 were detected in 85%, 10%, and 5% of affected patients, respectively. A total of 21 distinct variants of these three genes were identified. Exons 1 and 2 were the hotspot regions of the TYR variants, and c.895C > A and c.896G > A were the hotspot variants. We also found seven novel variants: c.731G > A, c.741C > A, c.867C > A, and c.1037‐2A > T in TYR, c.695dupT and c.1054A > G in OCA2, and c.9C > A in HPS1. Genetic tests on six fetuses revealed three carrier fetuses, two normal fetuses, and one affected fetus. The follow‐up results after birth were consistent with the results of prenatal diagnosis (one fetus terminated during pregnancy was not followed up).ConclusionsThis study expands our understanding of the genotypic spectrum of the Chinese OCA population. The findings indicate that prenatal diagnosis can provide important information for genetic counseling.

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.

Non-syndromic Oculocutaneous Albinism: Novel Genetic Variants and Clinical Follow Up of a Brazilian Pediatric Cohort.

Oculocutaneous albinism (OCA) is a genetic disorder characterized by skin, hair, and eye hypopigmentation due to a reduction or absence of melanin. Clinical manifestations include vision problems and a high susceptibility to skin cancer. In its non-syndromic form, OCA is associated with six genes and one chromosomal region. Because OCA subtypes are not always clinically distinguishable, molecular analysis has become an important tool for classifying types of OCA, which facilitates genetic counseling and can guide the development of new therapies. We studied eight Brazilian individuals aged 1.5–18 years old with clinical diagnosis of OCA. Assessment of ophthalmologic characteristics showed results consistent with albinism, including reduced visual acuity, nystagmus, and loss of stereoscopic vision. We also observed the appearance of the strabismus and changes in static refraction over a 2-year period. Dermatologic evaluation showed that no participants had preneoplastic skin lesions, despite half of the participants reporting insufficient knowledge about skin care in albinism. Whole-exome and Sanger sequencing revealed eight different mutations: six in the TYR gene and two in the SLC45A2 gene, of which one was novel and two were described in a population study but were not previously associated with the OCA phenotype. We performed two ophthalmological evaluations, 2 years apart; and one dermatological evaluation. To the best of our knowledge, this is the first study to perform clinical follow-up and genetic analysis of a Brazilian cohort with albinism. Here, we report three new OCA causing mutations.

Oculocutaneous Albinism with Squamous Cell Carcinoma, Bowen's Disease and Actinic Keratosis: A Case Report

Oculocutaneous Albinism with Squamous Cell Carcinoma, Bowen's Disease and Actinic Keratosis: A Case Report

Identification of Five Novel Variants in Chinese Oculocutaneous Albinism by Targeted Next-Generation Sequencing.

The diagnosis of oculocutaneous albinism (OCA) is established using clinical signs and symptoms. OCA is, however, a highly genetically heterogeneous disease with mutations identified in at least nineteen unique genes, many of which produce overlapping phenotypic traits. Thus, differentiating genetic OCA subtypes for diagnoses and genetic counseling is challenging, based on clinical presentation alone, and would benefit from a comprehensive molecular diagnostic. To develop and validate a more comprehensive, targeted, next-generation-sequencing-based diagnostic for the identification of OCA-causing variants. The genomic DNA samples from 28 OCA probands were analyzed by targeted next-generation sequencing (NGS), and the candidate variants were confirmed through Sanger sequencing. We observed mutations in the TYR, OCA2, and SLC45A2 genes in 25/28 (89%) patients with OCA. We identified 38 pathogenic variants among these three genes, including 5 novel variants: c.1970G>T (p.Gly657Val), c.1669A>C (p.Thr557Pro), c.2339-2A>C, and c.1349C>G (p.Thr450Arg) in OCA2; c.459_470delTTTTGCTGCCGA (p.Ala155_Phe158del) in SLC45A2. Our findings expand the mutational spectrum of OCA in the Chinese population, and the assay we developed should be broadly useful as a molecular diagnostic, and as an aid for genetic counseling for OCA patients.

Mutational analysis of a Chinese family with oculocutaneous albinism type 2.

Oculocutaneous albinism (OCA) is an autosomal recessive disorder characterized by hypopigmentation of the skin, hair, and eyes accompanied with ophthalmologic abnormalities. Molecular genetic test can confirm the diagnosis of the four subtypes of OCA (OCA1-4). Herein, we report a Chinese family with two patients affected by OCA. Mutations of TYR, OCA2, TYRP1, and SLC45A2 were examined by using PCR-sequencing. Large deletions or duplications of TYR and OCA2 were examined by Multiplex Ligation-dependent Probe Amplification (MLPA) assay. Compound heterozygous mutations of OCA2, (c.808-3C>G and c.2080-2A>G), were identified in both patients characterized with yellow hair and milky skin, heterochromia iridis, and nystagmus. Several computer-assisted approaches predicted that c.808-3C>G and c.2080-2A>G in OCA2 might potentially be pathogenic splicing mutations. No exon rearrangement (deletion/duplication) of TYR and OCA2 was observed in the patients by MLPA analysis. This study suggests that compound heterozygous mutations, (c.808-3C>G and c.2080-2A>G), in OCA2 may be responsible for partial clinical manifestations of OCA.

Identification of a functionally significant tri-allelic genotype in the Tyrosinase gene (TYR) causing hypomorphic oculocutaneous albinism (OCA1B)

Oculocutaneous albinism (OCA) and ocular albinism (OA) are inherited disorders of melanin biosynthesis, resulting in loss of pigment and severe visual deficits. OCA encompasses a range of subtypes with overlapping, often hypomorphic phenotypes. OCA1 is the most common cause of albinism in European populations and is inherited through autosomal recessive mutations in the Tyrosinase (TYR) gene. However, there is a high level of reported missing heritability, where only a single heterozygous mutation is found in TYR. This is also the case for other OCA subtypes including OCA2 caused by mutations in the OCA2 gene. Here we have interrogated the genetic cause of albinism in a well phenotyped, hypomorphic albinism population by sequencing a broad gene panel and performing segregation studies on phenotyped family members. Of eighteen probands we can confidently diagnose three with OA and OCA2, and one with a PAX6 mutation. Of six probands with only a single heterozygous mutation in TYR, all were found to have the two common variants S192Y and R402Q. Our results suggest that a combination of R402Q and S192Y with a deleterious mutation in a ‘tri-allelic genotype’ can account for missing heritability in some hypomorphic OCA1 albinism phenotypes.

More Than Skin Deep: Genetics, Clinical Manifestations, and Diagnosis of Albinism

Although albinism may be considered a simple diagnosis, its clinical manifestations, which include hypopigmenta- tion of the skin, hair, and eyes and ocular abnormalities such as nystagmus and reduced visual acuity, are often subtle and initially missed. In oculocutaneous albinism, there is wide phenotypic variability, which correlates with specific mutations in genes with roles in melanin biosynthesis. Additionally, syndromic forms of albinism such as Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, and Griscelli syndrome are associated with serious complications such as bleeding abnormalities, lysosomal storage defects, immunodeficient states, and progressive neurologic defects, which all can result in mortality. It is critical to confirm a suspicion of albinism and perform an appropriate workup involving molecular testing in order to establish a diagnosis. Given the various subtypes of oculocutaneous albinism and the life-threatening complications in syndromic forms of albinism, a diagnosis permits proper genetic counseling and timely implementation of necessary screenings and treatments. Recommendations regarding sun exposure and treatment of ocular abnormalities are imperative in oculocutaneous albinism, and preventive therapies should be implemented in syndromic forms. With knowledge of the differential in conjunction with the execution of simple diagnostic tests, many of these complications can be predicted and consequently ameliorated or prevented.

Refractive profile in oculocutaneous albinism and its correlation with final visual outcome

PurposeTo evaluate the prevalence of refractive errors in different subtypes of oculocutaneous albinism, and to see if there is any correlation between refractive errors and final visual outcome in this...

Tyrosinase gene analysis in Japanese patients with oculocutaneous albinism

Oculocutaneous albinism (OCA) is a heterogeneous congenital disorder. Tyrosinase is a key enzyme in melanin biosynthesis, and tyrosinase gene mutations cause the OCA1 subtype. This study was intended evaluate the frequency and details of tyrosinase gene mutations in Japanese OCA patients. We examined nine non-consanguineous OCA families, sequenced the tyrosinase gene of the patients and also confirmed a splicing site mutation using exon trapping system. Tyrosinase gene mutations were identified in five out of nine OCA families (55%). IVS2-10deltt-7t-a was present in 3 out of 18 alleles in three families (16%), P310insC was present in three alleles in three families (16%) and R278X was found in three alleles (16%), including those in one heterozygous and one compound homozygous patient. G97V (290 G-T) was found in 1 out of 18 alleles, and we could not find G97V in the mutation database. We have added this mutation as 9th mutation of Japanese OCA1 patients. In 8 of 18 alleles, four families, no tyrosinase mutations were identified. They were presumed not to be OCA1, but other subtypes of OCA. Exon trapping system demonstrated IVS2-10deltt-7t-a mutation generated the abnormal splicing site, and inserted the codon 4 bases in mRNA level resulting in premature termination codon downstream. This study provided new information about OCA1 mutations, and highlights the requirement of broader detailed search to make precise diagnosis of OCA.