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Disease Profile

Oculocutaneous albinism type 1B

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.
1-9 / 100 000

3,310 - 29,790

US Estimated

1-9 / 100 000

5,135 - 46,215

Europe Estimated

Age of onset

Infancy

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ICD-10

E70.3

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

Albinism, yellow mutant type; OCA1B; Yellow albinism;

Categories

Congenital and Genetic Diseases; Eye diseases; Metabolic disorders;

Summary

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.
orphanet

Orpha Number: 79434

Definition
Oculocutaneous albinism type 1B (OCA1B) is a type of OCA1 (see this term) characterized by skin and hair hypopigmentation, nystagmus, reduced iris and retinal pigment and misrouting of the optic nerves.

Epidemiology
The worldwide prevalence of OCA1 is estimated at 1/40,000. OCA1B is considered to account for about half of all overall OCA1 cases among non-Hispanic Caucasian patients.

Clinical description
Newborns have white or very light yellow hair but with age the hair can darken to blond or light brown. Eyelash hair can be darker than scalp and eyebrow hair. Skin remains creamy white but a minimal amount of tanning is possible along with freckles and pigmented nevi. Nytagmus is sometimes visible at birth but in others not until 3 to 4 months of age. It continues throughout life but becomes less rapid with age and is usually more noticeable in times of stress, anger or tiredness. Iris color is blue at birth and can change to brownish tan or greenish hazel or remain unchanged. Visual acuity ranges from 20/100 to 20/200. With time, skin can become rough, coarse and thickened if sun protection procedures are not followed. Patients have an increased risk of developing basal and squamous cell carcinomas but melanomas are rare.

Etiology
OCA1B is caused by a mutation in the TYR gene located on chromosome 11q14.2 encoding tyrosinase. The mutation causes the production of a partially active or hypomorphic tyrosinase enzyme that leads to minimal melanin formation in melanocytes.

Diagnostic methods
The characteristic clinical findings along with confirmatory genetic testing are used to diagnose OCA1B. Ophthalmologic examination reveals visualization of the choroidal blood vessels, reduced retinal pigment and foveal hypoplasia. Alternating strabismus, reduced stereoscopic vision, and an altered visual evoked potential (VEP) are associated with the characteristic misrouting of the optic nerves at the chiasm. Molecular genetic testing is necessary to obtain a definitive diagnosis, as some OCA1B patients have a certain degree of phenotypical variation which may lead to confusion in distinguishing it from other OCAs. This overlap of clinical symptoms emphasizes the importance of genetic analysis in the diagnosis of albinism.

Differential diagnosis
Differential diagnoses include the other forms of OCA and X-linked recessive ocular albinism (XLOA) as well as syndromes with albinism as a feature such as Hermansky-Pudlak syndromes 1-9, Chediak-Higashi syndrome, Griscelli syndromes 1-3, and Waardenburg syndrome type II (see these terms).

Antenatal diagnosis
Prenatal testing is theoretically possible for at risk pregnancies by molecular genetic testing although there are no reports of it having been performed.

Genetic counseling
This disorder is inherited autosomal recessively and genetic counseling is available.

Management and treatment
Annual ophthalmologic examination is necessary and corrective lenses or glasses are given to improve visual acuity. Dark glasses may be needed to relieve photophobia. Strabismus surgery can be performed for functional or cosmetic reasons. Protection from sunlight is imperative and patients should wear clothing and sunscreen on exposed skin to prevent burning and reduce the risk of skin cancer. Annual skin examinations should also be performed to identify any pre-cancerous or cancerous lesions.

Prognosis
OCA1B is not life threatening and remains stable after childhood. The medical and social consequences can however have major impacts on a patient's daily life.

Visit the Orphanet disease page for more resources.

Symptoms

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Abnormality of retinal pigmentation
0007703
Albinism
0001022
Freckling
0001480
Iris hypopigmentation
Light eye color
0007730
Strabismus
Cross-eyed
Squint
Squint eyes

[ more ]

0000486
30%-79% of people have these symptoms
Abnormality of the optic nerve
Optic nerve issue
0000587
Hypoplasia of the fovea
0007750
Melanocytic nevus
Beauty mark
0000995
Nystagmus
Involuntary, rapid, rhythmic eye movements
0000639
Photophobia
Extreme sensitivity of the eyes to light
Light hypersensitivity

[ more ]

0000613
Visual impairment
Impaired vision
Loss of eyesight
Poor vision

[ more ]

0000505
5%-29% of people have these symptoms
Basal cell carcinoma
0002671
Melanoma
0002861
Squamous cell carcinoma of the skin
0006739
Thickened skin
Thick skin
0001072
Percent of people who have these symptoms is not available through HPO
Autosomal recessive inheritance
0000007
Hypopigmentation of hair
Loss of hair color
0005599
Hypopigmentation of the fundus
0007894
Hypopigmentation of the skin
Patchy lightened skin
0001010

Diagnosis

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

    Organizations

    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Organizations Providing General Support

        Learn more

        These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

        In-Depth Information

        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Oculocutaneous albinism type 1B. Click on the link to view a sample search on this topic.