Chapter 20 :: Pigmentation and Melanocyte Biology

Question 1

brown/black melanin

Answer 1

(eumelanin)

Question 2

orange/yellow melanin

Answer 2

(pheomelanin)

Question 3

Waardenburg Syndrome

Answer 3

Piebaldism, congenital deafness, heterochromia irides, synophrys, broad nasal root, dystopia canthorum

Question 4

Hermansky-Pudlak syndrome (HPS)

Answer 4

Tyrosinase-positive oculocutaneous albinism (melanosome dysfunction) Bleeding diathesis (platelet granule dysfunction) Interstitial pulmonary fibrosis (HPS 1,2,4), granulomatous colitis (HPS 1,4), renal failure (rare), cardiomyopathy (rare) (caused by ceroidal lipofuscin accumulation in lysosomes) Neutropenia and cytotoxic T-cell dysfunction (HPS2)

Question 5

Chediak-Higashi syndrome

Answer 5

Tyrosinase-positive oculocutaneous albinism (melanosome dysfunction) Bleeding diathesis (platelet granule dysfunction) Progressive neurologic dysfunction (mechanism unknown) Severe immunodeficiency (NK cell, cytotoxic T cell, neutrophil dysfunction) Lymphomalike syndrome (overwhelming infiltration of organs by defective white blood cells) Giant lysosome-related organelles (these large granules are visible within leukocytes in peripheral blood smear)

Question 6

converts tyrosine to dopaquinone and is a key enzyme regulating both eumelanogenesis and pheomelanogenesis

Answer 6

Tyrosinase

Question 7

can shield against UV radiation

Answer 7

eumelanin

Question 8

decreased shielding property against UV radiation

Answer 8

Pheomelanin

Question 9

serves as a major source of sulfhydryl groups

Answer 9

Cysteine