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{{Albinism}} | {{Albinism}} | ||
{{CMG}}; {{AE}} {{ S.M}} | |||
==Overview== | |||
[[ Albinism]] is an inherited disease that is caused by a [[genetic mutation]]. This mutation impairs [[melanin]] synthesis; therefore, the number of [[melanocytes]] is preserved. The different types of [[albinism]] include, [[Oculocutaneous albinism]]([[OCA]]), [[Hermansky-Pudlak syndrome]] ([[HPS]]),[[Chediak-Higashi syndrome]] ([[CHS]]), and [[Ocular albinism]] ([[OA]]). Patients may present [[cutaneous]] and [[ocular]] findings. [[Cutaneous]] features include hypopigmented/ white [[hair]], [[skin]], and [[eyelashes]]. [[Ocular]] features include [[photophobia]], decreased [[visual acuity]], pink [[eyes]], and [[hypopigmentation]] of [[iris]], refractive errors, [[strabismus]], [[nystagmus]], [[foveal hypoplasia]], and [[iris]] transillumination. The management of [[cutaneous]] and [[ocular]] manifestations of [[albinism]] include avoidance of prolonged sun exposure, periodic [[dermatologist]] evaluation for [[skin cancer]], corrective lenses for refractive errors, tinted lenses/glasses for [[photophobia]], bifocal or low-vision aids in older children, eye-patching in [[infants]] for reduction of [[strabismus]], contact lenses or eye surgery in presence of [[nystagmus]]. Additionally, nitisinone can be used to improve [[pigmentation]] in OCA1. | |||
==Historical Perspective== | |||
[[Albinism]] was first discovered in 1908 by a British physician named Sir Archibald Edward Garrod. At first, it was believed that [[albinism]] is caused by a lack of [[melanocytes]]. In late 1950, it was proved that [[albinism]] is caused by [[tyrosine kinase]] inactivity. | |||
==Classification== | |||
[[Albinism]] is classified based on genetic [[mutation]]. The different types of [[albinism]] include [[Oculocutaneous albinism]]([[OCA]]), [[Hermansky-Pudlak syndrome]] ([[HPS]]),[[Chediak-Higashi syndrome]] ([[CHS]]), and [[Ocular albinism]] ([[OA]]). | |||
==Pathophysiology== | |||
[[Melanocytes]] are derived from [[neural crest]] [[ectoderm]] and are found in [[hair follicles]], [[skin]], [[eyes]], and [[inner ear]]. [[Melanocytes]] produce [[melanin]] which protects [[skin]] from [[ultraviolet]]. [[Tyrosinase]] converts [[tyrosine]] to [[DOPA]], [[dopaquinone]], and then [[melanin]]. [[Mutation]] in [[Tyrosinase]] [[enzyme]] is responsible for causing [[albinism]]. Additionally, [[melanin]] is responsible for development of the [[fovea]], [[optic nerves]], [[optic tracts]], and [[visual cortex]].Decussation of some optic nerve fibers at [[optic chiasm]] are essential for binocular vision. However, in [[albinism]], most of [[nerve fibers]] decussate at [[optic chiasm]] and cause monocluar vision presented as [[strabismus]]. In [[ocular albinism]], [[macular]] pigment is absent and [[fovea]] [[hypoplasia]] leads to decreased [[visual acuity]]. | |||
==Causes== | |||
[[Albinism]] is caused by [[genetic mutations]] that impair [[melanin]] synthesis. The number of [[melanocytes]] is preserved. | |||
==Differentiating Albinism from other Diseases== | |||
[[Oculocutaneous albinism]] and [[ocular albinism]] must be differentiated from the following rare disease: [[Hermansky-Pudlak syndrome]], [[Chediak-Higashi syndrome]], [[Griscelli syndrome]], [[Waardenburg syndrome]] type II, [[Vici syndrome]], Tietz albinism-deafness syndrome, [[Angelman syndrome]], [[Prader-Willi syndrome]], Cross-McKusick-Breen syndrome, [[Achromatopsia]], Aland Island eye disease (Forsius-Eriksson syndrome), [[Aniridia]], and [[Congenital]] [[nystagmus]]. | |||
==Epidemiology and Demographics== | |||
The [[prevalence]] of [[albinism]] is estimated to be 1:17,000 to 1: 20,000 in the general [[population]].The [[Prevalence]] of different types of [[albinism]] varies and the most prevalent form is [[Oculocutaneous albinism]] 2 ([[OCA2]]). | |||
==Risk Factors== | |||
[[Albinism]] is inherited due to [[genetic mutations]]. Individuals with positive [[familial history]] are at risk of having [[albinism]]. | |||
==Screening== | |||
There is no screening test for [[albinism]].Individuals with familial history of [[albinism]] can undergo [[genetic sequence]] analysis. | |||
==Natural History, Complications and Prognosis== | |||
The [[complications]] of [[albinism]] include [[skin cancer]], [[sunburn]], decreased [[visual]] acuity, poor self-image and self-isolation lead to [[depression]]. Patients with [[albinism]] has a normal [[life expectancy]] and do not have [[developmental delay]] or [[mental retardation]]. | |||
==Diagnosis== | |||
===History and Symptoms=== | |||
Patients may present both [[cutaneous]] and [[ocular]] findings. [[Cutaneous]] features include hypopigmented/ white [[hair]], [[skin]], and [[eyelashes]]. [[Ocular]] features include [[photophobia]], decreased [[visual acuity]], pink [[eyes]], and [[hypopigmentation]] of [[iris]]. | |||
===Physical Examination=== | |||
[[Ocular]] [[physical examination]] findings include refractive errors, [[strabismus]], [[nystagmus]], [[foveal hypoplasia]], [[iris]] transillumination, decreased [[iris]] [[pigmentation]]. Cutaneous finding varies from white to hypopigmented or light brown [[skin]], [[hair]], [[eyebrow]], and [[eyelashes]]. | |||
===Laboratory Findings=== | |||
The laboratory tests for diagnosis of [[albinism]] include [[hair bulb]] assay for determination of [[tyrosinase]] activity, [[Genetic sequence]] testing which is the most definite test, bleeding tests in suspected patients with [[Hermansky-Pudlak syndrome]], and evaluation of [[polymorphonuclear leukocyte]] function in suspected patients with [[Chediak-Higashi syndrome]]. | |||
=== Electrocardiogram=== | |||
There are no electrocardiogram findings associated with [[albinism]]. | |||
=== X Ray=== | |||
There are no x-ray findings associated with [[albinism]]. | |||
===CT=== | |||
There are no CT findings associated with [[albinism]]. | |||
== | ===MRI=== | ||
There are no MRI findings associated with [[albinism]]. | |||
=== Echocardiography or ultrasound=== | |||
There are no echocardiography or ultrasound findings associated with [[albinism]]. | |||
===Other Imaging Findings=== | |||
Macular optical coherence tomography can be used in young patients with [[nystagmus]] and [[foveal]] abnormalities to determine the cause. | |||
===Other Diagnostic Studies=== | |||
[[Ophthalmology]] examination and evaluation should be done to confirm the diagnosis. Visual-evoked potential testis used for recognition acuity in children and shows misrouting of optic nerves. | |||
==Treatment== | |||
===Medical Therapy=== | |||
The management of [[cutaneous]] and [[ocular]] manifestations of [[albinism]] include avoidance of prolonged sun exposure, periodic [[dermatologist]] evaluation for [[skin cancer]], corrective lenses for refractive errors, tinted lenses/glasses for [[photophobia]], bifocal or low-vision aids in older children, eye-patching in [[infants]] for reduction of [[strabismus]], contact lenses or eye surgery in presence of [[nystagmus]]. Additionally, nitisinone can be used to improve [[pigmentation]] in OCA1. | |||
===Surgery=== | |||
Eye muscles surgery can improve ocular alignment and [[vision]] in patients with severe [[ocular]] features. However, it may not be really helpful in [[strabismus]] improvement due to lack of necessary [[ocular]] connections. | |||
===Primary Prevention=== | |||
[[Genetic]] consultation is recommended for couples diagnosed with [[albinism]], familial history of [[albinism]] or parents of albino child who consider having future [[pregnancy]]. | |||
===Secondary Prevention=== | |||
There is no secondary prevention for [[albinism]]. | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
[[Category:Endocrinology]] | |||
[[Category:Dermatology]] | |||
[[Category:Needs content]] | [[Category:Needs content]] | ||
{{WS}} | |||
{{WH}} | |||
Latest revision as of 23:22, 23 August 2021
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shadan Mehraban, M.D.[2]
Overview
Albinism is an inherited disease that is caused by a genetic mutation. This mutation impairs melanin synthesis; therefore, the number of melanocytes is preserved. The different types of albinism include, Oculocutaneous albinism(OCA), Hermansky-Pudlak syndrome (HPS),Chediak-Higashi syndrome (CHS), and Ocular albinism (OA). Patients may present cutaneous and ocular findings. Cutaneous features include hypopigmented/ white hair, skin, and eyelashes. Ocular features include photophobia, decreased visual acuity, pink eyes, and hypopigmentation of iris, refractive errors, strabismus, nystagmus, foveal hypoplasia, and iris transillumination. The management of cutaneous and ocular manifestations of albinism include avoidance of prolonged sun exposure, periodic dermatologist evaluation for skin cancer, corrective lenses for refractive errors, tinted lenses/glasses for photophobia, bifocal or low-vision aids in older children, eye-patching in infants for reduction of strabismus, contact lenses or eye surgery in presence of nystagmus. Additionally, nitisinone can be used to improve pigmentation in OCA1.
Historical Perspective
Albinism was first discovered in 1908 by a British physician named Sir Archibald Edward Garrod. At first, it was believed that albinism is caused by a lack of melanocytes. In late 1950, it was proved that albinism is caused by tyrosine kinase inactivity.
Classification
Albinism is classified based on genetic mutation. The different types of albinism include Oculocutaneous albinism(OCA), Hermansky-Pudlak syndrome (HPS),Chediak-Higashi syndrome (CHS), and Ocular albinism (OA).
Pathophysiology
Melanocytes are derived from neural crest ectoderm and are found in hair follicles, skin, eyes, and inner ear. Melanocytes produce melanin which protects skin from ultraviolet. Tyrosinase converts tyrosine to DOPA, dopaquinone, and then melanin. Mutation in Tyrosinase enzyme is responsible for causing albinism. Additionally, melanin is responsible for development of the fovea, optic nerves, optic tracts, and visual cortex.Decussation of some optic nerve fibers at optic chiasm are essential for binocular vision. However, in albinism, most of nerve fibers decussate at optic chiasm and cause monocluar vision presented as strabismus. In ocular albinism, macular pigment is absent and fovea hypoplasia leads to decreased visual acuity.
Causes
Albinism is caused by genetic mutations that impair melanin synthesis. The number of melanocytes is preserved.
Differentiating Albinism from other Diseases
Oculocutaneous albinism and ocular albinism must be differentiated from the following rare disease: Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, Griscelli syndrome, Waardenburg syndrome type II, Vici syndrome, Tietz albinism-deafness syndrome, Angelman syndrome, Prader-Willi syndrome, Cross-McKusick-Breen syndrome, Achromatopsia, Aland Island eye disease (Forsius-Eriksson syndrome), Aniridia, and Congenital nystagmus.
Epidemiology and Demographics
The prevalence of albinism is estimated to be 1:17,000 to 1: 20,000 in the general population.The Prevalence of different types of albinism varies and the most prevalent form is Oculocutaneous albinism 2 (OCA2).
Risk Factors
Albinism is inherited due to genetic mutations. Individuals with positive familial history are at risk of having albinism.
Screening
There is no screening test for albinism.Individuals with familial history of albinism can undergo genetic sequence analysis.
Natural History, Complications and Prognosis
The complications of albinism include skin cancer, sunburn, decreased visual acuity, poor self-image and self-isolation lead to depression. Patients with albinism has a normal life expectancy and do not have developmental delay or mental retardation.
Diagnosis
History and Symptoms
Patients may present both cutaneous and ocular findings. Cutaneous features include hypopigmented/ white hair, skin, and eyelashes. Ocular features include photophobia, decreased visual acuity, pink eyes, and hypopigmentation of iris.
Physical Examination
Ocular physical examination findings include refractive errors, strabismus, nystagmus, foveal hypoplasia, iris transillumination, decreased iris pigmentation. Cutaneous finding varies from white to hypopigmented or light brown skin, hair, eyebrow, and eyelashes.
Laboratory Findings
The laboratory tests for diagnosis of albinism include hair bulb assay for determination of tyrosinase activity, Genetic sequence testing which is the most definite test, bleeding tests in suspected patients with Hermansky-Pudlak syndrome, and evaluation of polymorphonuclear leukocyte function in suspected patients with Chediak-Higashi syndrome.
Electrocardiogram
There are no electrocardiogram findings associated with albinism.
X Ray
There are no x-ray findings associated with albinism.
CT
There are no CT findings associated with albinism.
MRI
There are no MRI findings associated with albinism.
Echocardiography or ultrasound
There are no echocardiography or ultrasound findings associated with albinism.
Other Imaging Findings
Macular optical coherence tomography can be used in young patients with nystagmus and foveal abnormalities to determine the cause.
Other Diagnostic Studies
Ophthalmology examination and evaluation should be done to confirm the diagnosis. Visual-evoked potential testis used for recognition acuity in children and shows misrouting of optic nerves.
Treatment
Medical Therapy
The management of cutaneous and ocular manifestations of albinism include avoidance of prolonged sun exposure, periodic dermatologist evaluation for skin cancer, corrective lenses for refractive errors, tinted lenses/glasses for photophobia, bifocal or low-vision aids in older children, eye-patching in infants for reduction of strabismus, contact lenses or eye surgery in presence of nystagmus. Additionally, nitisinone can be used to improve pigmentation in OCA1.
Surgery
Eye muscles surgery can improve ocular alignment and vision in patients with severe ocular features. However, it may not be really helpful in strabismus improvement due to lack of necessary ocular connections.
Primary Prevention
Genetic consultation is recommended for couples diagnosed with albinism, familial history of albinism or parents of albino child who consider having future pregnancy.
Secondary Prevention
There is no secondary prevention for albinism.