Albinism

Albinism (achromia, achromasia, achromatosis) is defined as a group of inherited disorders characterized by a deficit in the production of melanin with deficiency or absence of pigment in the skin, hair and eyes.

  • Processes: congenital
  • Incidence: 0 / 100.000

Overview

Albinism is a group of inherited disorders characterized by a deficit in the production of melanin with deficiency or absence of pigment. The disorder is also known as achromia, achromatosis, or achromasia [1]. The condition is classified in two forms, ocular albinism (OA) and oculocutaneous albinism (OCA), which are divided into several subtypes based on the location of the genetic mutation, (OCA 1, OCA 2, OCA 3) and (OA1, AROA).

Along with the loss of pigment, the condition can also be associated with vision problems including nystagmus, astigmatism, and photophobia. In relation to the skin, albinism is associated with various skin cancers and chronic sunburns.

Etiology

  • The cause of albinism type OCA 1 and AROA, lies in a defective enzyme called tyrosinase. This enzyme contains copper and is involved in the production of melanin and other pigments from tyrosine by oxidation [2]. The tyrosinase enzyme is encoded by the TYR gene with the gene location 11q14-21. 
  • Mutations in tyrosinase-related protein 1 (TRP1), coded on chromosome 9 cause OCA 3. 
  • Mutation to the P gene, enconding for P protein which plays a role in regulating the pH of melanosomes, causes OCA 2.

Epidemiology

Albinism can affect people from all ethnic backgrounds. According to reports, it occurs in about one person out of 17,000 people worldwide. A patient’s lifespan is not affected by albinism as there is no link between the condition and mortality [3]. In general, a person’s health will remain normal aside from the associated conditions. 

Pathophysiology

A congenital hypopigmentation within the systemic and ocular tissues is present [4]. Cellular pigmentation relies on the individual cell’s capability to manufacture as well as isolate the melanin pigment. This process happens inside organelles known as melanosomes. These are found in the melanocyte cells of the iris’s stroma, the ciliary body, choroid pigments, the skin, the conjunctive of the eye, and the hair. Melanin is synthesised through tyrosine inside of the melanosome.

Tyrosinase plays a dominant role in albinism and affected individuals are therefore classified as being tyrosinase-positive or tyrosinase-negative depending on the results of a hair bulb test or an electron microscopy of the skin or hair. In both cases, there is usually an autosomal recessive inheritance pattern detected. If a patient is found to be tyrosinase-negative, the enzyme is considered to be inactive. This stops the cell from using the enzyme in order to produce melanin pigment. In the opposite case, the activity level of the tyrosinase enzyme is actually normal, but the cell is unable to synthesize the melanin due to defects in other enzymes involved in the pathway.

Prognosis

While albinism has no effect on a patient’s lifespan, it can limit their activities. Due to the sensitive nature of the skin, daily activities in normal sunlight might prove to be difficult without some layer of protection. Sunlight or other bright lights might affect vision due to the eyes’ sensitivity.

Presentation

The main sign of albinism is the lack of pigment in skin, eyes, and hair. Other symptoms include vision difficulties. Common signs and symptoms are [6]:

  • Pink skin. However, skin color can vary from white to a brown and may even be seen as a normal hue. Skin can also change in children and teens as melanin production increases during the teenage years.
  • The appearance of freckles or moles on exposed skin.
  • White hair. Patients of Asian or African descent might present yellow, red, or brown hair that may darken over the years.
  • Light blue to brown eyes and translucent irises. 
  • Nystagmus, photophobia, astigmatism, strabismus, or extreme farsightedness or nearsightedness can be seen.

Workup

After a physical examination coupled with a description of pigmentation changes, and familial comparisons, albinism can usually be diagnosed [7]. The physical exam will also be paired with an eye exam. A genetic test is necessary in order to confirm albinism and detect which specific subtype of the condition is present. 

Treatment

There is no cure for albinism, only management measures that a patient is recommended to follow [9]. A patient experiencing vision problems may be prescribed glasses, bifocals, or other vision aids. If a patient is experiencing strabismus, eye patches, especially for infants, or surgery might be beneficial. Tinted glasses may be used to improve photophobia. 

Other recommendations concern the protection of the patient’s sensitive skin. Wearing a hat while in the sun, using sunblock on exposed skin, or wearing long sleeves and pants is recommended. 

Prevention

This is a genetic condition so prevention is not possible. If patients are concerned about passing down the trait to their children, they are able to seek genetic counselling for help [10].

Patient Information

Albinism is an inherited condition distinguishable by the absence of melanin pigment in the patient. This pigment is responsible for the color of a person’s hair, eyes, and skin. The condition is usually accompanied by a sensitivity to the sun and is linked to an increased risk of various skin problems including skin cancer. Vision problems are also associated with albinism.

Albinism can affect people from all ethnic background. It is genetic and can’t be caused by outside influences.

There is no cure for albinism, but there are a number of things that a person can do to manage the condition. Using protective layers including sunscreen and loose clothes is recommended to protect sensitive skin. Eyeglasses can be prescribed for vision problems and sunglasses are recommended when outdoors.

Some people may also experience nonmedical issues due to their albinism. This can include social isolation and discrimination. These issues can be handled with the help of a therapist or other counsellor who can help a patient work through these social problems.

References

  1. Summers CG. Albinism: classification, clinical characteristics, and recent findings. Optom Vis Sci. Jun 2009;86(6):659-62. 
  2. Schiaffino MV, Tacchetti C. The ocular albinism type 1 (OA1) protein and the evidence for an intracellular signal transduction system involved in melanosome biogenesis. Pigment Cell Res. Aug 2005;18(4):227-33.
  3. Innamorati G, Piccirillo R, Bagnato P, Palmisano I, Schiaffino MV. The melanosomal/lysosomal protein OA1 has properties of a G protein-coupled receptor. Pigment Cell Res. Apr 2006;19(2):125-35.
  4. Wang T, Waters CT, Jakins T, et al. Temperature sensitive oculocutaneous albinism associated with missense changes in the tyrosinase gene. Br J Ophthalmol. Oct 2005;89(10):1383-4.
  5. Ramsay M, Colman MA, Stevens G, et al. The tyrosinase-positive oculocutaneous albinism locus maps to chromosome 15q11.2-q12. Am J Hum Genet. Oct 1992;51(4):879-84. 
  6. Kaplan J, De Domenico I, Ward DM. Chediak-Higashi syndrome. Current Opinion in Hematology 2008 15 (1): 22–29.
  7. Kruijt B et al. Ocular straylight in albinism. Optom Vis Sc 2011;88:E585-E592
  8. Carden SM, Boissy RE, Schoettker PJ, Good WV. Albinism: modern molecular diagnosis. The British Journal of Ophthalmology 1998 82 (2): 189–95.
  9. Gronskov K, Ek J, Brondum-Nielsen K (2 November 2007). "Oculocutaneous albinism". Orphanet Journal of Rare Diseases 2: 43.
  10. Lee J. Surgical management of nystagmus. Journal of the Royal Society of Medicine 2002 95 (5): 238–41.

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