Inherited Retinal Dystrophies

Question 1

Describe Retinitis Pigmentosa (RP)?

Answer 1

• NOT inflammatory disorder of retina
• Group of disorders characterised by loss of photoreceptors  primarily rods, but later affecting cones
• Many different genetic defects know to cause RP
  o Can be inherited as autosomal dominant, recessive or X-linked
• Retina alone may be affected or may be other systemic effects, e.g. deafness in Usher’s syndrome

Question 2

Symptoms and signs of RP?

Answer 2

o Night blindness
o Loss of peripheral vision – restricted VF
o Pigment in peripheral retina – abnormal “bone spicule” pigmentation –> pigmentation may be absent or not obvious
o Reduced or flat ERG (electroretinogram)

Question 3

Describe Stargardt’s disease? What are the signs & symptoms?

Answer 3

• Caused by mutation in ABCA4 gene – which codes for a protein which helps to remove products of Vitamin A metabolism in the 2 photoreceptors
• Pxs start to lose central vision in their teens or twenties
• Retina has pale spots called flecks
• RPE atrophy at macula
  o Easily detected with autofluorescence photography

Question 4

What is Best’s disease? What are the signs & symptoms?

Answer 4

• Macular dystrophy
• Initial “egg yolk” appearance at macula – caused by protein deposition under RPE
• Later there is pigment deposition & egg yolk disappears accompanied by declining vision
  o Reduced vision in 40s & 50s
• EOG (electrooculogram) is usually reduced or unrecordable

-Initial egg yolk appearance is usually compatible with good vision
-Later, as RPE atrophy sets in, vision starts to decline

Question 5

Inherited Disease Management?

Answer 5

• No treatment available at present
• Leber’s amaurosis
  o One of most severe forms of congenital RP caused by mutation in RPE65 gene
  o Luxturna has been licensed for use – gene therapy for Leber’s amaurosis
   Not a cure & will not restore normal vision
• Ensure partial sight/blind registration
• Low vision aids & mobility training
• Genetic counselling may be appropriate
• Ensure people with inherited retinal disorders are given support they need & have access to accurate info regarding their prognosis & risk of passing it on to their children