nur 350 HEALTH ASSESSMENT
BYSTANDER
Albinism.pptxALBINISM
ALBINISM
Albinism is inherited
Consist of several abnormalities of melanin synthesis
Can have reduced or absent melanin production
The effects of hypopigmentation can affect the eyes as well
Different combinations of gene mutations effect the severity of the hypopigmentation
Melanin production is impaired due to a defect in the ability to make melanin from tyrosine (Bashour, 2020).
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PATHOPHYSIOLOGY
Melanin has functions in the brain and the eyes, but these functions are not well understood
When melanin is not present during development the fovea does not develop properly; The retina will develop normally
The effects of albinism on the eyes causes predominantly monocular vision and a decrease in binocular depth perception
The scattering of light often causes photophobia and a decrease in visual acuity
Foveal hypoplasia most commonly is the main reason for decreased visual acuity
Melanocytes are present in the hair follicles, eyes, and the skin
Melanin pathways exist to convert tyrosine into the 2 forms of melanin
Black-brown eumelanin and red-blond pheomelanin
Mutations on the melanin pathways inhibit or impair this conversion causing reduction or absence of melanin
Enzymes that normally function in this pathway are
Tyrosinase (converts tyrosine to DOPA and then to dopaquinone)
Dopaquinone (converts to eumelanin or pheomelanin)
Tyrosinase-related protein 1 (TRP1) and Tyrosinase-related protein 2 (TRP2)
P protein aids in the transport of tyrosine (Bashour, 2020).
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Melanin is necessary for ocular development
Mutation to the tyrosinase enzyme produces either OCA 1 or AROA.
Mutation to the TRP1 gene causes OCA 3. Mutation to the TRP2 gene does not produce albinism.
Mutation to this P gene produces OCA 2.
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DIAGNOSIS
Genetic sequence analysis reveals a diagnosis
Helpful in families with known albinism
Not a screening tool
Hair bulb assays can help to reveal the status of the tyrosinase activity
Severe albinism is relatively easy to diagnose
Difficulty arises when diagnosing milder subtypes of albinism
Macular optical coherence tomography
(Bashour, 2020; Campell et al., 2019)
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Signs & Symptoms
Begin examining the hair, and skin for sign of hypopigmentation
Comprehensive eye exam
Silt-lamp evaluation
Dilated fundus exam
May detect a refractive error, astigmatism, nystagmus, strabismus, fovea hypoplasia
Assess for iris depigmentation
Decreased sense of depth perception
Assess phenotype
Complete lack of pigmentation in the hair or skin is indicative of OCA 1A
White hair at birth is always indicative OCA 1
Minimal melanin may indicate OCA 1B, OCA 2, or OCA 3
To differentiate these gene sequencing must be done (Bashour, 2020).
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Epidemiology
The frequency worldwide is approximately one in 17,000
There are 18,000 people in the U.S. with albinism.
Albinism can occur in any race.
Albinism, in all its subtypes are usually congenital
With X-linked inheritance it is much more common to see albinism in boy s than in girls.
Around the world 1 in 40,000 have OCA 1 albinism.
OCA 2 is most prevalent and most commonly affects African Americans and Africans at a rate of 1 in 10,000;
This albinism occurs in 1 in 36,000 whites.
Hermansky-Pudlak syndrome (HPS) is most prevalent in patients in Puerto Rico occurring in 1 in 2,700.
HPS is not common in other parts of the world. (Bashour, 2020: Jaurgeui et al, 2018).
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Patient & Family Education
Melanin protects the skin from the sun
Lack of melanin causes skin to burn easily
Instruct patient to avoid sun exposure
Encourage patient/family to see genetic counseling
Exposure to light can cause retinal damage which can worsen visual acuity
Consultation with a hematologist if Chediak-Higashi syndrome (CHS) or Hermansky-Pudlak syndrome (HPS) are present
Rawf8 / Getty Images
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References
Bashour, M. (2020). Albinism. https://emedicine.medscape.com/article/1200472-overview#a4 Campbell, P., Ellingford, J. M., Parry, N. R. A., Fletcher, T., Ramsden, S. C., Gale, T., Hall, G., Smith, K., Kasperaviciute, D., Thomas, E., Lloyd, I. C., Douzgou, S., Clayton-Smith, J., Biswas, S., Ashworth, J. L., Black, G. C. M., & Sergouniotis, P. I. (2019). Clinical and genetic variability in children with partial albinism. Scientific Reports (Nature Publisher Group), 9, 1–10. http://dx.doi.org/10.1038/s41598-019-51768-8 Jauregui, R., Huryn, L. A., & Brooks, B. P. (2018). Comprehensive review of the genetics of albinism. Journal of Visual Impairment & Blindness (Online), 112(6). https://search.proquest.com/central/docview/2166315220/abstract/A684F1488D404013PQ/1
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