INDEX/ / / / / /

Albinism






Albinism describes a group of genetic alterations of the melanin pigment system that affect skin, hair follicles, and eyes. It principally involves the synthesis of melanin in these sites, but a normal number of melanocytes is present; also included are some alterations of the pathways of the CNS. Albinism can affect the eyes, ocular albinism (X-linked recessive or autosomal recessive), or the eyes and skin, oculocutaneous albinism (OCA). In OCA, the disorder is autosomal recessive, with dilution of normal amounts of skin, hair, and melanin pigment; nystagmus and iris translucency are always present, and there is a reduction of visual acuity, sometimes severe enough to cause severe impairment of vision.



Causes:

The defect in melanin synthesis has been shown to result from absence of the activity of the enzyme tyrosinase. Tyrosinase is a copper-containing enzyme that catalyzes the oxidation of tyrosine to dopa and the subsequent dehydrogenation of dopa to dopa-quinone. Recent cloning of complementary DNAs (cDNAs) encoding tyrosinase has made it possible to directly characterize the mutations in the tyrosinase gene responsible for deficient tyrosinase activity in several types of albinism. In type IA, two different missense mutations, one from each parent, result in amino acid substitutions within one of the two copper-binding sites.



Symptoms:

* Rapid eye movements
* Strabismus (eyes not tracking properly)
* Photophobia (avoidance of light because of discomfort)
* Decreased visual acuity or even functional blindness
* Albinismus
* BADS
* Congenital Achromia
* Hypopigmentation
* Oculocutaneous Albinism

INDEX/ / / / / /