Albinism

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  1. Variable inheritance (locus heterogeneity); vs ocular albinism (x-linked recessive).
  2. Congenital deficiency of either
    1. tyrosinase(can’t make melanin from tyrosine; aut-rec);
    2. defective tyrosine transporters (dec. tyrosine = dec. melanin); can also be from lack of migration of neural crest cells.
  3. Increased. risk skin cancer

Exam MCQ

A newborn has milky white skin, white hair, and redappearing eye color (see the fi gure below). This disorder most often results from a defect in which of the following enzymes?

(A) Phenylalanine hydroxylase

(B) NADPH oxidase

(C) Dihydrofolatereductase

(D) Tyrosinase

(E) Homogentisic acid oxidase

2 The answer is D:

Tyrosinase. The child has albinism, a lack of pigment in the skin cells, which is produced by melanocytes. Melanocyte tyrosinase (a different isozyme than the neuronal tyrosinase that produces DOPA for catecholamine biosynthesis) is defective in albinism. The DOPA produced is then used for pigment production. A lack of phenylalanine hydroxylase leads to PKU. A lack of dihydrofolatereductase is most likely a lethal event as there are no reported cases of a lack of this enzyme. Tetrahydrofolate is not required for the conversion of tyrosine to DOPA in melanocytes. NADPH oxidase generates superoxide, which is not part of this pathway. Homogentisic acid is part of the phenylalanine and tyrosine degradation pathways, and is not involved in albinism.

Exam MCQ

Pick out the correct statement regarding albinism:

A.         Increased tyrosinase activity will be observed in melanocytes

B.         It results in photophobia

C.         Mental retardation is the main characteristic feature in albinism

D.         Skin has high pigmentation in albinism

ANS:B. Albinism is due to defect in tyrosinase enzyme, which is required for the synthesis of melanin in melanocytes from tyrosine. Lack of melanin pigment in the eyes, albinos sensitive to sunlight (photophobia), skin has low pigmentation. Mental retardation is not observed in albinism.

 

  1. Variable inheritance (locus heterogeneity); vs ocular albinism (x-linked recessive).
  2. Congenital deficiency of either
    1. tyrosinase(can’t make melanin from tyrosine; aut-rec);
    2. defective tyrosine transporters (dec. tyrosine = dec. melanin); can also be from lack of migration of neural crest cells.
  3. Increased. risk skin cancer

Exam MCQ

A newborn has milky white skin, white hair, and redappearing eye color (see the fi gure below). This disorder most often results from a defect in which of the following enzymes?

(A) Phenylalanine hydroxylase

(B) NADPH oxidase

(C) Dihydrofolatereductase

(D) Tyrosinase

(E) Homogentisic acid oxidase

2 The answer is D:

Tyrosinase. The child has albinism, a lack of pigment in the skin cells, which is produced by melanocytes. Melanocyte tyrosinase (a different isozyme than the neuronal tyrosinase that produces DOPA for catecholamine biosynthesis) is defective in albinism. The DOPA produced is then used for pigment production. A lack of phenylalanine hydroxylase leads to PKU. A lack of dihydrofolatereductase is most likely a lethal event as there are no reported cases of a lack of this enzyme. Tetrahydrofolate is not required for the conversion of tyrosine to DOPA in melanocytes. NADPH oxidase generates superoxide, which is not part of this pathway. Homogentisic acid is part of the phenylalanine and tyrosine degradation pathways, and is not involved in albinism.

Exam MCQ

Pick out the correct statement regarding albinism:

A.         Increased tyrosinase activity will be observed in melanocytes

B.         It results in photophobia

C.         Mental retardation is the main characteristic feature in albinism

D.         Skin has high pigmentation in albinism

ANS:B. Albinism is due to defect in tyrosinase enzyme, which is required for the synthesis of melanin in melanocytes from tyrosine. Lack of melanin pigment in the eyes, albinos sensitive to sunlight (photophobia), skin has low pigmentation. Mental retardation is not observed in albinism.


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An inside look into the lives of South Africans with albinism; a story of the challenges and the triumphs of living in a country where they are largely marginalized by others who struggle to place them into the proverbial “rainbow nation”. Albinism is a medical condition, yet the social manifestations of albinism are faced on a daily basis by those affected by it. Through the stories of Sphonakaliso Mpisi and Jake Scott, the many myths and misconceptions surrounding people with albinism are tackled in an attempt to bring an end to the ignorance that persists.
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In Kenya, people with albinism say they stand out because they’re different, and they have to face discrimination as well as possible heath risks.
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