Albinism

Question 1

Where is melanin in the eye

Answer 1

• RPE (retinal pigmented epithelium) (originates from neuroectoderm)
• uveal melanocytes (originate from neural crest cells)

Question 2

underdevelopment of fovea in Albinism

Answer 2

need pigment for fovea to form induction did not happen b/c no pigment to reduce formation of fovea

Question 3

eumelanin

Answer 3

browns, blacks, tanning

Question 4

phtomelanin

Answer 4

red
poor tanning

Question 5

First step in making pigment (eumelanogenesis) is the conversion of ? to ? by enzyme ?

Answer 5

• tyrosine to DOPA
• tyrosinase

tyrosinase function is implicated in albinism

Question 6

Type 1 OCA
* inheritance pattern
* gene

Answer 6

• AR
• TYR

truly tyrosinase negative, no melanin, severe

Question 7

Type IB OCA
* presentation/type of variant
* amount of tyrosinase activity

Answer 7

• “yellow variant” (yy or y/t-)
• white at birth
• white tipped hair (sandy blonde)
• moderate pigment later (pheomelanin) (pheo compensating for eu)
• 7& tyrosinase activity

Question 8

Tyrosinase is temperature sensitive so can result in

Answer 8

no tyrosinase in warm areas - so no pigment

Question 9

Type I OCAs are all…

Answer 9

tyrosinase negative or very low

Question 10

less tyrosinase =

Answer 10

less pigment

Question 11

Type II OCA relation to tyrosinase

Answer 11

• “tyrosinase positive”
• unrelated to tyrosinase
• variants in the p gene
• maintenance and health of melanosomes affected

Question 12

Hermansky-Pudlak Syndrome

Answer 12

• macromelanosomes (hold pigment)
• bleed easily
  *

Question 13

Chediak-Higashi
* tyrosinase activity
* pigment
* age of onset
* gene

Answer 13

• “tyrosinase positive” OCA
• metallic grey sheen to hair and slate grey patches on skin
• death in childhood
• CHS

Question 14

Most common form of albinism

Answer 14

XLr ocular albinism

Question 15

melanocytes originate from…

Answer 15

neural crest cells