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What is Retinitis Pigmentosa and early signs of RP in childhood?

A stem-cell based therapy for Retinitis Pigmentosa

What is Retinitis Pigmentosa (RP)?

Retinitis Pigmentosa is a group of genetically inherited eye disorders leading to gradual deterioration of the retina and loss of vision. Children and adults with RP experience a slow decline in vision as the photoreceptor cells in the retina degenerate.

Some of the diseases in the RP group include: Usher syndrome, Rod-Cone disease, Bardet-Biedl syndrome, Lebers congenital amaurosis and Refsum disease.

While the exact number is unknown, there are approximately 1 lakh children and adults in India with RP. RP can appear in infancy, early childhood, adolescence or adulthood. The rate of degeneration depends on the individual, however most people affected by RP are legally blind by the age of 40. In some cases like in Usher syndrome, RP also leads to deafness.

RP can be inherited as an autosomal recessive disorder (from both parents who are carriers) or as an autosomal dominant disorder (from one parent who is affected).

In some cases, RP can be an X-linked disorder where the mother carries the mutated gene on the X-chromosome. In this case, the sons have 50% chance of inheriting RP and daughters have a 50% chance of becoming a carrier.

The most common types of RPs are:
  • Usher syndrome
  • Lebers Congenital Amaurosis (LCA)
  • Rod-cone disease
  • Bardet-Biedl syndrome
  • CMV (cytomegalovirus) retinitis which is a type of retinitis which develops after a viral infection in the eye.
Symptoms of RP depend on whether the rods or cones are involved. Most types of RP involve damage to the rods. The degeneration of the rods impact peripheral and night vision. As the disease progresses, even the cones get destroyed and ultimately the person’s visual acuity, color perception and central vision deteriorate. In the later stages of degeneration, the person starts experiencing tunnel vision. In CMV retinitis, the early stages may go unnoticed. Later stage symptoms include:
  • loss of side vision
  • blurred vision
  • floaters like clouds or specks
Retinitis can be diagnosed with a number of approaches:
  • Visual field testing – can help measure side vision and detect blind spots
  • Electroretinography – measures the electrical activity in the retina and determines how well the retina responds to light
  • Optical coherence tomogrophy (OCT) – this imaging technique takes detailed photographs of the retina and it helps diagnose RP
  • Genetic testing – can enable the detection of genes involved in causing RP

Currently, no permanent cure is available for all types of RP. Gene therapy research is in progress along with other novel treatments like valproic acid. In December 2017, the FDA approved Spark Therapeutics’ gene therapy Luxturna for patients with RPE65 mutation and Leber congenital amaurosis (LCA). However, the cost remains a huge barrier and challenge.

Current treatment for all types of RP is aimed at preserving eyesight and enabling independent living. Most patients are prescribed vitamin A palmitate. Patients with low vision are usually able to use several assistive devices to enable independent living and work.

If there is a known case of RP in the family, it is absolutely essential for closest female relatives like siblings, uncles, aunts and cousins to test for carrier status.

If a woman with a carrier status is pregnant, prenatal test is essential to determine if the fetus has the disease mutation.