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AOS1 - Week 8 > Albinism and its Ocular Manifestations > Flashcards

Albinism and its Ocular Manifestations Flashcards

1
Q

What is Albinism?

A

The result of reduced or absent melanin biosynthesis

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2
Q

What are the two classification groups of Albinism?

A
  • Oculocutaneous albinism (OCA)
  • Ocular albinism (OA)
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3
Q

What is melanin?

A

melanin is produced and contained within melanosomes which is an organelle within melanocytes and retinal pigment epithelium

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4
Q

What is the classification of oculocutaneous?

A
  • hypopigmentation of the skin, hair and eyes
    due to a reduction in, or a complete lack of production of melanin
  • high degree of heterogeneity in pigmentation presentation
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5
Q

What is the classification of ocular albinism?

A

hypopigmentation primarily affecting the retinal pigment epithelial cells
- hair and skin remain pigmented

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6
Q

What are the 7 genetics of oculocutaneous?

A
  • OCA1 : TYR
  • OCA2 : OCA2
  • OCA3 : TYPRP1
  • OCA4 : SLC45A2
  • OCA5 : chromosome location known but gene not defined
  • OCA6 : SLC24A5
  • OCA7 : C10orf11
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7
Q

What is an AR mutation?

A

Androgen receptor

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8
Q

What is the OCA1 gene?

A

two subtypes OCA1A (^severe) and OCA1B
TYR encodes tyrosinase the most important enzyme in melanin biosynthesis

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9
Q

What is the OCA2 gene?

A

OCA2 encodes P-protein, a melansome membrane protein

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10
Q

What is the OCA3 gene?

A

Also known as known as Rufous oculocutaneous albinism
TYRP1 encodes tyrosinase-related protein 1

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11
Q

What is the OCA4 gene?

A
  • it encodes a melanosome membrane protein
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12
Q

What is the OCA5 gene?

A

A non-syndromic AR cause of OCA

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13
Q

What is the OCA6 gene?

A
  • it encodes for the NCKX5 protein
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14
Q

What is the OCA7 gene?

A

encodes a 198 amino acid protein with 3 leucine-rich repeats and its associated with melanocyte differentiation

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15
Q

What are the signs and symptoms?

A
  • Visual disturbances
  • High degree of heterogeneity in pigmentation presentation depending upon the gene
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16
Q

What is the colouration of OCA1A?

A
  • hair, eyelashes and eyebrows are white
  • skin is white and does not tan
  • pigment does not develop through life
17
Q

What is the colouration of OCA1B?

A
  • typically born with white hair, eyelashes, eyebrows and pale skin
  • develop some melanin pigment in hair and lashes over time
  • skin may tan - freckles
18
Q

What is the colouration of OCA2?

A
  • degree of skin pigmentation varies, pale at birth
  • nearly always have pigmented hair at birth often blonde or red
19
Q

What is the colouration of OCA3?

A

Red hair and reddish-brown skin

20
Q

What is the colouration of OCA5?

A

golden-coloured hair and white skin

21
Q

What is the coloration of OCA6?

A
  • Hair colour varies from white to blonde or dark brown
  • hair darkens with age
22
Q

What is the colouration of OCA7?

A

pigmentation varies
- present with lighter pigmentation than unaffected relatives

23
Q

What is the iris colour for OCA1A?

A

light blue to almost pink, fully translucent

24
Q

What is the iris colour of OCA1B?

A

blue irides that may change to green/brown with age

25
Q

What is the iris colour of OCA2?

A

Variable iris colour
- blue eyes may become light brown

26
Q

What is the iris colour of OCA3?

A

hazel to brown eyes

27
Q

What is the iris colour for OCA4?

A

Variable iris colour
- blue eyes may become light brown

28
Q

What is the iris colour for OCA5?

A

described as depigmented

29
Q

What is the iris colour of OCA6?

A

heterogenous, ranging from no pigmentation and full transillumination to blue or brown

30
Q

What is the iris colour of OCA7?

A

lighter pigmentation than normal relatives

31
Q

What happens with the retina and albinism?

A
  • delayed retinal development occurs
  • foveal pit typically absent
  • overall reduction in rod numbers
32
Q

What happens with albinism and the macular?

A
  • macula region remains underdeveloped
  • thinning of the macula inner and outer nuclear layers
33
Q

Why do albinos experience glare?

A

OCA1A results in severe photophobia and glare due to complete lack of iris pigmentation

AOS1 - Week 8 (3 decks)

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