SEARCH · PubMed Health

Results for “Albinism, Oculocutaneous”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2003

Oculocutaneous albinism.

Oculocutaneous albinism represents a group of inherited skin disorders characterized by a generalized reduction of cutaneous, ocular and pilar pigmentation from the time of birth. Oculocutaneous albinism types 1 and 2 are the most common, but several other types have been described. A defect in the melanin synthesis pathway, resulting in reduced formation of melanin, is responsible for oculocutaneous albinism. Aetiology, clinical manifestations, diagnosis and management are discussed.

Albinism, Oculocutaneous↗

PubMed1996

Mutations of the tyrosinase gene in three Korean patients with type I oculocutaneous albinism.

Oculocutaneous albinism (OCA) is an inherited disorder of the melanin pigmentary system, characterized by a decrease or an absence of melanin in the skin, hair, and eyes. Type I (tyrosinase-deficient) OCA results from mutations of the tyrosinase (TYR) gene encoding tyrosinase, the enzyme that catalyzes at least the first two steps of melanin biosynthesis. We have analyzed the TYR gene in three Korean patients with severe type I OCA. Two patients were compound heterozygotes for the Arg (CGG) to Gln (CAG) mutation at position 77 and a C insertion mutation at position 310. The other was a compound heterozygote for a C insertion mutation at position 310 and the Asp (GAT) to Asn (AAT) mutation at position 383. These mutations were easily detected by restriction enzyme digestion or by SSCP analysis. Such methods of mutation analysis thus provide a basis for a screening system for the TYR gene mutations in Korean patients with type I OCA.

Albinism, Oculocutaneous↗

PubMed2000

Electron microscopic DOPA reaction test for oculocutaneous albinism.

Oculocutaneous albinism (OCA) is an autosomal recessive disorder in which the biosynthesis of melanin is reduced or absent in skin, hair and eyes. Tyrosinase-related OCA (OCA1) is caused by mutations in the tyrosinase gene. Tyrosinase-negative OCA (OCA1A) is the most severe phenotype in which tyrosinase catalytic activity is completely lost, resulting in no mature melanin pigment. Yellow OCA (OCA1B) varies from very little pigment associated with whitish-blond hair to nearly normal pigment with dark-blond hair and skin. We determined the tyrosinase activity in melanocytes by the electron microscopic dihydroxyphenylalanine (EM-DOPA) reaction test using skin samples and analyzed tyrosinase gene mutations in nine Japanese patients with OCA. In 18 alleles of nine patients, the OCA1A-associated mutations, P310insC, R77Q and R278X, were found in seven, three and one alleles, respectively. Five patients who had these mutations in both alleles showed white hair, blue eyes and white skin and demonstrated no tyrosinase activity by the EM-DOPA reaction test. Three patients who had no tyrosinase gene mutation showed tyrosinase activity and heterogeneous clinical features. One patient in whom only an R77Q OCA1A mutation was found in one allele demonstrated a reduced tyrosinase activity, indicating OCA1B. This patient had white hair at birth, but it had turned blond by the age of 1 year. These results indicate that the EM-DOPA reaction test provides clear information on the status of tyrosinase activity which is essential for the identification of the disease subtype which in turn is important for the prognosis of patients with OCA.

Adult↗

PubMed1994

African origin of an intragenic deletion of the human P gene in tyrosinase positive oculocutaneous albinism.

Oculocutaneous albinism (OCA) is a genetically heterogeneous hypopigmentation disorder. One of the two major autosomal recessive forms involves the tyrosinase gene (OCA1), while the other form (OCA2) has recently been associated with alterations of the P gene on chromosome 15. OCA2 is about twice as common as OCA1 in African and African-American populations. We now describe an interstitial deletion that removes a single exon of the P gene. In a large family from an inbred population of tri-racial origin, all individuals with OCA2 were found to be homozygous for this allele. Moreover, the same mutant P allele was detected in several unrelated African American individuals with OCA2, but not in Caucasians with OCA2. The detection of the same allele in two unrelated Africans with OCA2 indicates an African origin for this allele.

Africa↗

PubMed1994

Molecular basis of oculocutaneous albinism.

Oculocutaneous albinism (OCA) is a complex group of genetic disorders that have historically been defined by clinical and biochemical methods. Recent advances in the molecular biology of pigmentation have greatly increased our understanding of the complexity of this group of disorders. To date, two different types of OCA (OCA1 and OCA2) have been mapped to specific chromosomal regions. Mutations have been found in the tyrosinase locus associated with OCA1 and the human homologue to the murine pink-eyed dilution locus associated with OCA2. Analysis of these genes and their mutations will allow us to better define and categorize the different types of albinism. Further, the analysis of these genes and their mutations will provide information on the role of these gene products in melanin biosynthesis and the effect specific mutations have on the pathogenesis of albinism.

Albinism, Oculocutaneous↗

PubMed1992

[Oculocutaneous albinism].

Oculocutaneous albinism (OCA) is an inherited condition characterized by hypopigmentation of the skin, hair, and eyes. Ocular involvement is often severe with photophobia, decreased visual acuity due to foveal hypoplasia, nystagmus, and strabism secondary to defective routing of optic axons in the chiasma. Cutaneous hypopigmentation is responsible for diminished photoprotection that places patients at increased risk for skin cancers. OCA also occurs in a number of life-threatening conditions, including Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, and Griscelli-Prunieras syndrome. Most cases of OCA are inherited on an autosomal recessive basis. Several mutations have recently been identified in type I OCA or "tyrosinase-negative" OCA. Identification of other genetic abnormalities will probably occur in the future and will lead to more accurate classification of OCA syndromes.

Albinism, Oculocutaneous↗

PubMed1993

Molecular genetics of oculocutaneous albinism.

Oculocutaneous albinism (OCA) is a group of autosomal recessive disorders characterized by deficient synthesis of melanin pigment. Type I (tyrosinase-deficient) OCA results from deficient enzymatic activity of tyrosinase, which catalyzes at least three steps in the melanin biosynthetic pathway. Type II (tyrosinase-positive) OCA results from abnormalities of the "P" polypeptide. Recent application of molecular genetic techniques to the study of these disorders has led to extraordinary advances in knowledge of their molecular pathogenesis, paving the way to improved diagnosis, carrier detection, and even treatment.

Albinism, Oculocutaneous↗

PubMed2003

Oculocutaneous albinism type 1: the last 100 years.

Research on human albinism has been central to many of the major discoveries in human genetics. These include the first evidence that Mendel's rules of genetic segregation apply to humans, first published in 1903. Contrary to initial thought that albinism is caused by mutations in a single gene, we now know that the genetics of albinism are complex. The complexity of albinism was hinted at, in early publications, but has only recently been fully appreciated with the advent of molecular techniques. Currently, 12 different genes have been identified, that when mutated, result in a different type of albinism. Oculocutaneous albinism type 1 (OCA1), resulting from mutations of the tyrosinase gene, is genetically and biochemically the best understood type of albinism. Though much of the research in albinism has involved OCA1, there are many unanswered questions about OCA1 and albinism, in general. The next 100 yr should still provide many surprises as did the first 100 yr.

Albinism, Oculocutaneous↗

PubMed1996

Might the refractive state in oculocutaneous albino patients be a clue for distinguishing between tyrosinase-positive and tyrosinase-negative forms of oculocutaneous albinism?

In oculocutaneous albinism (OCA), one can distinguish between a tyrosinase-negative form (no residual activity of the enzyme tyrosinase) and a tyrosinase-positive form (with detectable residual enzymatic activity) and their respective subtypes. In infancy and early childhood the clinical discrimination between tyrosinase-positive OCA and tyrosinase-negative OCA can be very difficult. To date, only the hair-bulb L-dopa incubation test has been helpful in discriminating between the tyrosinase (ty)-negative and ty-positive forms of OCA. In 68 patients with albinism of the eye, 24 had an oculocutaneous form of albinism. We determined the ty relationship either by the L-dopa incubation test (younger patients) or by clinical appearance (older patients). We determined the full cycloplegic refraction in all patients and looked for a possible correlation of the refraction with the ty relationship. Our data suggest that an OCA patient with a hyperopic refractive error of > 4.0 D might have a ty-positive form of OCA. A patient with a moderate to high degree of myopia is more likely to have a ty-negative form of OCA. Determination of ty relationship is more reliable in patients with high degrees of hyperopia and, therefore, in patients with a ty-positive form of OCA. Statistical evaluation of the data was not possible in a sensible way due to the small number of patients involved in the present study.

Adolescent↗

PubMed2004

Tyrosinase gene analysis in Japanese patients with oculocutaneous albinism.

BACKGROUND: Oculocutaneous albinism (OCA) is a heterogeneous congenital disorder. Tyrosinase is a key enzyme in melanin biosynthesis, and tyrosinase gene mutations cause the OCA1 subtype. OBJECTIVE: This study was intended evaluate the frequency and details of tyrosinase gene mutations in Japanese OCA patients. PATIENTS AND METHODS: 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. RESULTS: 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. CONCLUSION: This study provided new information about OCA1 mutations, and highlights the requirement of broader detailed search to make precise diagnosis of OCA.

Adolescent↗

PubMed2001

Mutations in the human orthologue of the mouse underwhite gene (uw) underlie a new form of oculocutaneous albinism, OCA4.

Oculocutaneous albinism (OCA) affects approximately 1/20,000 people worldwide. All forms of OCA exhibit generalized hypopigmentation. Reduced pigmentation during eye development results in misrouting of the optic nerves, nystagmus, alternating strabismus, and reduced visual acuity. Loss of pigmentation in the skin leads to an increased risk for skin cancer. Two common forms and one infrequent form of OCA have been described. OCA1 (MIM 203100) is associated with mutations of the TYR gene encoding tyrosinase (the rate-limiting enzyme in the production of melanin pigment) and accounts for approximately 40% of OCA worldwide. OCA2 (MIM 203200), the most common form of OCA, is associated with mutations of the P gene and accounts for approximately 50% of OCA worldwide. OCA3 (MIM 203290), a rare form of OCA and also known as "rufous/red albinism," is associated with mutations in TYRP1 (encoding tyrosinase-related protein 1). Analysis of the TYR and P genes in patients with OCA suggests that other genes may be associated with OCA. We have identified the mouse underwhite gene (uw) and its human orthologue, which underlies a new form of human OCA, termed "OCA4." The encoded protein, MATP (for "membrane-associated transporter protein") is predicted to span the membrane 12 times and likely functions as a transporter.

Adult↗

PubMed2006

[A new form of Oculocutaneous albinism, OCA4].

Oculocutaneous albinism (OCA) is a complex genetic disease with great clinical heterogeneity. Four different types of OCA have been reported to date (OCA1, OCA2, OCA3, and OCA4). OCA4 was firstly reported in a Turkish OCA patient. The gene responsible for OCA4 is the human homologue of the mouse underwhite (uw) gene, which encodes the mem-brane-associated transporter protein (MATP). MATP gene is located on chromosome 5p13.3 and is divided into 7 exons and 6 introns. MATP gene is transcriptionally modulated by MITF, and encodes a protein of 530 amino acids. There are at least 18 pathologic mutations and 8 non-pathologic polymorphisms have been found.

Albinism, Oculocutaneous↗

PubMed1993

Mutations of the tyrosinase gene in Indo-Pakistani patients with type I (tyrosinase-deficient) oculocutaneous albinism (OCA).

Oculocutaneous albinism (OCA) is a group of autosomal recessive disorders characterized by deficient synthesis of melanin pigment. Type I (tyrosinase-deficient) OCA results from mutations of the tyrosinase gene (TYR gene) encoding tyrosinase, the enzyme that catalyzes the first two steps of melanin biosynthesis. Mutations of the TYR gene have been identified in a large number of patients, most of Caucasian ethnic origin, with various forms of type I OCA. Here, we present an analysis of the TYR gene in eight Indo-Pakistani patients with type I OCA. We describe four novel TYR gene mutations and a fifth mutation previously observed in a Caucasian patient.

Adolescent↗

PubMed1994

Ophthalmic features of minimal pigment oculocutaneous albinism.

PURPOSE: The purpose of this study is to describe the heterogeneous phenotype of individuals with an unusual type of albinism--minimal pigment oculocutaneous albinism. METHODS: Nine patients with minimal pigment oculocutaneous albinism were identified and followed for up to 11 years. The criteria were the presence of oculocutaneous albinism in association with low hairbulb tyrosinase activity in the patient and disparate activity in the parents with one parent having normal activity and the other having low tyrosinase activity. Changes in skin, hair, and ocular pigment were followed as the patients matured. As a measure of ocular pigment, iris transillumination and macular transparency were graded according to a previously published scheme. RESULTS: Patients were born with white scalp hair and skin, and nystagmus developed. Visual acuity was reduced to 20/50 to 20/200 for the group, but in one patient vision improved with maturity. Irides were blue. In seven patients, iris pigment developed, which was detected by transillumination with slit-lamp biomicroscopy, including the one patient with improved visual acuity. All patients had foveal hypoplasia, and melanin pigment in the fundi could not be detected by clinical examination. Visual acuity in the group did not correlate directly with the presence or development of iris transillumination or macular transparency. The pedigrees were consistent with an autosomal recessive inheritance pattern. CONCLUSION: This unique type of oculocutaneous albinism has heterogeneous clinical features. Minimal pigment oculocutaneous albinism appears to represent a new type of tyrosinase-related oculocutaneous albinism (OCA1MP).

Adolescent↗

PubMed1990

[Eumelanin and pheomelanin contents in hairs of healthy Japanese and patients with oculocutaneous albinism, and 5-S-cysteinyldopa and 5-hydroxy-6-methoxyindole-2-carboxylic acid levels in urine of oculocutaneous albinism].

The contents of eumelanin and pheomelanin in the scalp hairs of 4 Japanese patients with total albinism (3 tyrosinase-positive and one negative) and 100 healthy Japanese were measured by the melanin microquantitation method of Ito and Fujita. The urinary 5-S-Cysteinyldopa (5-S-CD) and 5-Hydroxy-6-Methoxyindole-2-Carboxylic acid (5H6MI2C) contents in the 4 albino subjects were also determined. Our findings included that (1) Regardless of ge, black hairs of all the healthy subjects contained phemelanin at a level of about 5% of the total melanin contents. The hair color of the 3 tyrosinase-positive subjects was pale-yellow, and their hairs contained only pheomelanin. The hair color of the one tyrosinase-negative subject was white, and neither eumalanin nor pheomelanin could be detected. (2) Urinary 5H6M12C, an indicator of eumelanin production in the body, could not be detected in either the tyrosinase-positive or tyrosinase-negative subjects, while the urinary 5-S-CD content of the tyrosinase-negative subject was much lower than that of the tyrosinase-positive subjects. These results suggested that the yellow hair color of patients with tyrosinase-positive albinism is attributable to the production of only pheomelanin and that the urinary 5-S-CD content does not necessarily reflect the ability to produce melanin.

Adolescent↗

PubMed2004

Mutations in the MATP gene in five German patients affected by oculocutaneous albinism type 4.

Oculocutaneous albinism (OCA) is caused by a deficiency of melanin synthesis and characterized by generalized hypopigmentation of skin, hair, and eyes. Due to the hypopigmentation of the retinal pigment epithelium, OCA is usually associated with congenital visual impairment, in addition to an increased risk of skin cancer. OCA is a genetically heterogeneous disease with distinct types resulting from mutations in different genes involved in the pathway which results in pigmentation. OCA1 is associated with mutations in the TYR gene encoding tyrosinase. OCA2 results from mutations in the P gene encoding the P protein and is the most common form of OCA. OCA3, also known as rufous/red albinism, is caused by mutations in the TYRP1 gene, which encodes the tyrosinase-related protein 1. Recently, OCA4 was described as a new form of OCA in a single patient with a splice site mutation in the MATP gene (or AIM1), the human ortholog of the murine underwhite gene. The similarity of MATP to transporter proteins suggests its involvement in transport functions, although its actual substrate is still unclear. We screened 176 German patients with albinism for mutations within the MATP gene and identified five individuals with OCA4. In this first report on West European patients, we describe 10 so far unpublished mutations, as well as two intronic variations, in addition to two known polymorphisms.

Adult↗

PubMed1992

Molecular analysis of type I-A (tyrosinase negative) oculocutaneous albinism.

Type I oculocutaneous albinism (OCA) is caused by the reduction in or absence of activity of tyrosinase in melanocytes in skin, hair, and the eyes, the result of mutations of the tyrosinase gene. To date, a total of 22 unique mutations in the coding region of tyrosinase have been described in the literature. In this report we present 5 additional mutations of the tyrosinase gene associated with type I-A OCA in four individuals, including 2 missense, 1 frameshift and 2 nonsense mutations, and review the relevant literature on all published mutations. Analysis of the distribution of all identified missense mutations (n = 17) shows that most cluster in three areas of the gene and involve amino acids conserved between humans and the mouse. Two clusters involve the copper A and copper B binding sites and may disrupt the metal ion-protein interaction necessary for enzyme function. The third cluster in exon I could represent a functional domain important in enzyme function such as the tyrosine or the dihydroxyphenylalanine (DOPA) binding site of the enzyme. Small deletions or insertions resulting in frameshift mutations and nonsense mutations are distributed throughout the coding region and do not appear to cluster.

Albinism, Oculocutaneous↗

PubMed2004

Oculocutaneous albinism type 4 is one of the most common types of albinism in Japan.

Oculocutaneous albinism (OCA) is a complex genetic disease with great clinical heterogeneity. Four different types of OCA have been reported to date (OCA1, OCA2, OCA3, and OCA4). MATP was recently reported in a single Turkish OCA patient as the fourth pathological gene, but no other patients with OCA4 have been reported. Here, we report the mutational profile of OCA4, determined by genetic analysis of the MATP gene in a large Japanese population with OCA. Of 75 unrelated patients that were screened, 18 individuals (24%) were identified as having OCA4; they harbored seven novel mutations, including four missense mutations (P58S, D157N, G188V, and V507L) and three frameshift mutations (S90CGGCCA-->GC, V144insAAGT, and V469delG), showing that MATP is the most frequent locus for tyrosinase-positive OCA in Japanese patients. We discuss the functional melanogenic activity of each mutant allele, judging from the relationship between the phenotypes and genotypes of the patients. This is the first report on a large group of patients with OCA4.

Adolescent↗