Retinitis Pigmentosa

  • Post author:Mohaimen Al-Zubaidy, Mustafa Al-Zubaidy
  • DOIDOI:10.48089/jfo7868029
  • Reader Impact RatingImpact Rating: 7.13 / 10 from 207 reader votes.

Dr Mohaimen Al-Zubaidy – MBBS BSC (Hons) – F2 Newcastle University Healthcare Trust

Mr Mustafa Al-Zubaidy – Medical Student at Imperial College London

Introduction

Retinitis pigmentosa (RP) is defined as a spectrum of hereditary disorders affecting the photoreceptors and retinal pigment epithelium, leading to progressive peripheral visual loss and night blindness. Retinitis pigmentosa is a leading cause of blindness worldwide and currently, many therapeutic challenges stand in the way of an approved therapy to stop degeneration and restore vision (1).

The condition is commonly known as progressive pigmentary retinopathy and rod-cone dystrophy and is typically classified into non-syndromic and syndromic retinitis pigmentosa (2).

Here we will further discuss the presentations of retinitis pigmentosa, its underlying pathophysiology and the diagnostic steps taken by clinicians to recognise RP as well as the management of these patients.

Epidemiology

With a prevalence of 1 in 5000 worldwide, retinitis pigmentosa is the most common inherited disease of the retina (3) and on average is diagnosed around the age of 35 years (4).

Risk Factors

Family history is the strongest known predisposing factor for development of retinitis pigmentosa with multiple modes of inheritance encountered. Similarly, the presence of other associated syndromes such as Usher’s syndrome has been found to predispose patients to developing the condition (5).

Pathophysiology

Retinitis pigmentosa is caused by the loss of photoreceptors (rod and cone cells) and deposition of pigment in the peripheral retina, sparing the central retina (6). Inheritance patterns of the condition can commonly be autosomal dominant, X-linked or autosomal recessive, with rare cases reporting mitochondrial inheritance (5).

Within the retina, cone photoreceptors are organised centrally and rod photoreceptors peripherally each with a respective function (7). Cone depletion affects visual fields under photopic conditions and leads to reduced visual acuity, loss of colour vision and light sensitivity (8). Rod depletion affects visual fields under scotopic conditions, reduces visual acuity as well as hindering light to dark adaptation (8).

In some cases, isolated cone dystrophy may occur. Rod photoreceptors are the first to degenerate commonly, followed by the cone photoreceptors (rod-cone dystrophy), but various genes may lead to the degeneration of cones first followed by rods (cone-rod dystrophy) (9).

Clinical Presentation

Various ocular symptoms are the main presentations of retinitis pigmentosa, with visual loss being gradual and progressive. Symptoms typically depend on the type of photoreceptor affected initially.

Some of the earliest symptoms include difficulty driving due to poor night vision and poor adaptation to dark environments. Patients may report bumping into furniture or doors due to loss of peripheral vision which is a feature that is only commonly noticed as the disease progresses (10).

In different cone-rod types of retinitis pigmentosa, patients may complain of difficulty reading or seeing detail due to central vision loss. As the macula continues to function, most patients will maintain light perception to an extent, even in the later disease stages (11).

Investigations

In all suspected cases of retinitis pigmentosa, patients should undergo a full ophthalmologic examination consisting of fundoscopy, retinal function assessment and visual field examination.

A full field electroretinography (ERG) is usually performed to measure the electrical activity of photoreceptors in the retina, it is essential for diagnosis and monitoring progression. Abnormal ERG with a decrease in amplitude and latency is characteristically seen in retinitis pigmentosa (12).

Patients with RP may present with the clinical triad of arteriolar attenuation, retinal pigmentary changes and waxy disc pallor.

Management

Whilst there is ongoing research into treatment for RP including gene therapy, there are currently no standard definitive treatments for patients affected. Some studies have shown Vitamin A supplementation to slow the rate of retinal deterioration and thus this has been the most recommended treatment at present (13).

Conclusion

To conclude, RP is a hereditary condition characterized by progressive degeneration of the retina secondary to the dysfunction of the retinal pigment epithelium. It is important for us as clinicians to be able to recognise the clinical features associated with RP early and continue to monitor the latest research for any future breakthroughs in management.

References

  1. Sahni JN, Angi M, Irigoyen C, Semeraro F, Romano MR, Parmeggiani F. Therapeutic challenges to retinitis pigmentosa: from neuroprotection to gene therapy. Curr Genomics. 2011 Jun;12(4):276-84. doi: 10.2174/138920211795860062. PMID: 22131873; PMCID: PMC3131735.
  2. Ferrari S, Di Iorio E, Barbaro V, Ponzin D, Sorrentino FS, Parmeggiani F. Retinitis pigmentosa: genes and disease mechanisms. Curr Genomics. 2011 Jun;12(4):238-49. doi: 10.2174/138920211795860107. PMID: 22131869; PMCID: PMC3131731.
  3. O’Neal TB, Luther EE. Retinitis Pigmentosa. 2020 Sep 5. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30137803.
  4. Tsujikawa M, Wada Y, Sukegawa M, Sawa M, Gomi F, Nishida K, Tano Y. Age at onset curves of retinitis pigmentosa. Arch Ophthalmol. 2008 Mar;126(3):337-40. doi: 10.1001/archopht.126.3.337. PMID: 18332312.
  5. Daiger SP, Bowne SJ, Sullivan LS. Genes and Mutations Causing Autosomal Dominant Retinitis Pigmentosa. Cold Spring Harb Perspect Med. 2014 Oct 10;5(10):a017129. doi: 10.1101/cshperspect.a017129. PMID: 25304133; PMCID: PMC4588133.
  6. Hartong DT, Berson EL, Dryja TP. Retinitis pigmentosa. Lancet. 2006 Nov 18;368(9549):1795-809. doi: 10.1016/S0140-6736(06)69740-7. PMID: 17113430.
  7. Molday RS, Moritz OL. Photoreceptors at a glance. J Cell Sci. 2015 Nov 15;128(22):4039-45. doi: 10.1242/jcs.175687. PMID: 26574505; PMCID: PMC4712787.
  8. Hamel C. Retinitis pigmentosa. Orphanet J Rare Dis. 2006 Oct 11;1:40. doi: 10.1186/1750-1172-1-40. PMID: 17032466; PMCID: PMC1621055.
  9. Hamel CP. Cone rod dystrophies. Orphanet J Rare Dis. 2007 Feb 1;2:7. doi: 10.1186/1750-1172-2-7. PMID: 17270046; PMCID: PMC1808442.
  10. Hartong DT, Berson EL, Dryja TP. Retinitis pigmentosa. Lancet. 2006 Nov 18;368(9549):1795-809. doi: 10.1016/S0140-6736(06)69740-7. PMID: 17113430.
  11. O’Neal TB, Luther EE. Retinitis Pigmentosa. 2020 Sep 5. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30137803.
  12. Verbakel SK, van Huet RAC, Boon CJF, den Hollander AI, Collin RWJ, Klaver CCW, Hoyng CB, Roepman R, Klevering BJ. Non-syndromic retinitis pigmentosa. Prog Retin Eye Res. 2018 Sep;66:157-186. doi: 10.1016/j.preteyeres.2018.03.005. Epub 2018 Mar 27. PMID: 29597005.
  13. Shintani K, Shechtman DL, Gurwood AS. Review and update: current treatment trends for patients with retinitis pigmentosa. Optometry. 2009 Jul;80(7):384-401. doi: 10.1016/j.optm.2008.01.026. PMID: 19545852.
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