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Ocular System

Retinitis pigmentosa (RP)

Inherited retinal dystrophy caused by the loss of photoreceptors and characterized by retinal pigment deposits visible on fundus examination.

Inherited retinal dystrophy caused by the loss of photoreceptors and characterized by retinal pigment deposits visible on fundus examination.

  • Type of pigmentary retinopathy
  • M/C hereditary fundus dystrophy

Clinical hallmarks:

  1. Abnormal fundus with bone-spicule deposits and attenuated retinal vessels
  2. Anormal, diminished or absent a- and b-waves in the electroretinogram (ERG)
  3. Reduced visual field

Classification

Non-syndromic RP:

  • Autosomal dominant RP (adRP) (best prognosis)
  • Autosomal recessive RP (arRP) (M/C)
  • X-Linked RP (xlRP) (rarest, worst prognosis)
  • Leber congenital amaurosis 
  • Digenic RP (very rare)

Syndromic and systemic RP (20-30% cases):

Atypical RP with associated non-ocular disease
  • Usher syndrome (USH) (M/C syndromic RP, 10%): Autosomal recessive disease characterized by the association of hearing loss, retinitis pigmentosa (RP), and, in some cases, vestibular dysfunction.
  • Bardet-Biedl syndrome (BBS) (5%): Characterized by rod-cone dystrophy (>90%), truncal obesity (72%), postaxial polydactyly, cognitive impairment, male hypogonadotrophic hypogonadism, complex female genitourinary malformations, and renal abnormalities.
  • Kearn-Sayre syndrome
  • Refsum syndrome
  • Bassen-Kornzweig syndrome
  • Neuropathy, ataxia & retinitis pigmentosa (NARP)

Presentation

Loss of vision (due to photoreceptor apoptosis):

Night blindness → ↓ Visual fields → Tunnel vision → Legal blindness → Complete blindness

Case study:

Diagnosis

Functional signs:

  • Night blindness (nyctalopia) (earliest symptom)
  • Photophobia (appears later)
  • Visual acuity (preserved in early and mid stages)

Visual field:

  • Patchy losses of peripheral vision evolving to:
    • Ring shape scotoma → Tunnel vision

Fundus:

  • Classic triad:
    1. Bony-spicule retinal pigmentation
    2. Arteriolar attenuation
    3. Optic disc pallor
  • Other findings: Subscapular cataracts, macular edema
Fundus of patient with retinitis pigmentosa, early stage
Fundus of patient with retinitis pigmentosa, mid stage
Fundus of patient with retinitis pigmentosa, end stage

Electroretinogram (ERG):

  • Dramatic diminution in a- and b-wave’s amplitudes
  • Scotopic system (rods) predominates over photopic (cones) system
ERG recordings in a normal patient and one with retinitis pigmentosa
ERG recordings in a normal patient and one with retinitis pigmentosa | Creel DJ. Clinical Electrophysiology. 2005 May 1 [Updated 2007 Jul 2]. In: Kolb H, Fernandez E, Nelson R, editors. Webvision: The Organization of the Retina and Visual System [Internet]. Salt Lake City (UT): University of Utah Health Sciences Center; 1995-. Figure 13, [ERG recordings in a normal patient and one with retinitis pigmentosa.]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK11553/figure/ch36clinicalerg.F13/

Management

No standard treatments for patients with retinitis pigmentosa (RP)

High-dose Vitamin A supplementation + LFT monitoring:

Slow the rate of retinal deterioration

Voretigene

Gene therapy approved for RPE-65 gene associated RP

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