Retinitis pigmentosa
Retinitis pigmentosa | |
---|---|
Other names | Inherited Retinal Dystrophy/Diseases |
Vitamin A palmitate[1] | |
Frequency | 1 in 4,000 people[1] |
Retinitis pigmentosa (RP) is a
Retinitis pigmentosa is generally inherited from one or both parents.
There is currently no cure for retinitis pigmentosa.
Currently there is only one FDA-approved gene therapy that is commercially available to RP patients with Leber congenital amaurosis type 2. It replaces the miscoded RPE65 protein that is produced within the retinal pigmented epithelium. It has been found to effectively work in about 50% of the patients who receive the therapy. The earlier the child receives the RPE65 therapy the better the chances for a positive outcome. There are many other therapies being researched at this time with the goal of being approved in the next few years.
It is estimated to affect 1 in 4,000 people.[1]
Signs and symptoms
The initial retinal degenerative symptoms of retinitis pigmentosa are characterized by decreased night vision (nyctalopia) and the loss of the mid-peripheral visual field.[4] The rod photoreceptor cells, which are responsible for low-light vision and are orientated mainly in the retinal periphery, are the retinal processes affected first during non-syndromic (without other conditions) forms of this disease.[5] Visual decline progresses relatively quickly to the far peripheral field, eventually extending into the central visual field as tunnel vision increases. Visual acuity and color vision can become compromised due to accompanying loss of the cone photoreceptor cells, which are responsible for color vision, visual acuity, and sight in the central visual field.[5] The progression of disease occurs in both eyes in a similar but not identical pattern. A variety of indirect symptoms characterize retinitis pigmentosa along with the direct effects of the initial rod photoreceptor degeneration and later cone photoreceptor decline. Phenomena such as photophobia, which describes the event in which light is perceived as an intense glare, and photopsia, the presence of blinking, swirling or shimmering lights spontaneously occurring within the visual field, often manifest during the later stages of RP.
Findings related to RP have often been characterized in the fundus (back layer) of the eye as the "ophthalmic triad". This includes the development of (1) a mottled appearance of the retina and retinal pigment epithelium (RPE) that gives the same visual appearance of b one spicule patterns (but are not bone spicules), (2) a waxy yellow appearance of the
Non-syndromic RP (RP appears alone without other co-morbidities) usually presents a variety of the following symptoms:[citation needed]
- Night blindness
- Tunnel vision (due to loss of peripheral vision)
- Latticework vision[clarification needed]
(due to patchy loss of peripheral vision)
- loss of depth perception[6]
- Photopsia (Spontaneously occurring flashes/blinking/swirling/shimmering lights)
- Photophobia (aversion to bright lights)
- Development of the appearance of melanin pigment in a bone spicule pattern in the fundus (not bone tissue)
- Slow adjustment from dark to light environments and vice versa
- Blurring of vision
- Poor color separation
- Loss of central vision is the last to go, because this is a disease of the rods and not the cones which are the highest in number in the Central Vision (Macula and Fovea)
- Eventual blindness (legally defined as 20 degrees or less in the best seeing eye or visual acuity of 20/200 or worse. The majority of patients do not become totally blind, often retaining limited or non-functional vision.
Causes
RP may be: (1) non-syndromic, that is, it occurs alone, without any other clinical findings, (2) syndromic, with other neurosensory disorders,
- RP combined with deafness (congenital or progressive) is called Usher syndrome.[8]
- Alport's syndrome is associated with RP and an abnormal glomerular-basement membrane leading to nephrotic syndrome. It is inherited as X-linked dominant.
- RP combined with ophthalmoplegia, dysphagia, ataxia, and cardiac conduction defects is seen in the mitochondrial DNA disorder Kearns–Sayre syndrome (also known as Ragged Red Fiber Myopathy).
- RP combined with intellectual disability, peripheral neuropathy, acanthotic (spiked) RBCs, ataxia, steatorrhea, and absence of VLDL is seen in abetalipoproteinemia.[9]
- RP is seen clinically in association with several other rare genetic disorders (including muscular dystrophy and chronic granulomatous disease) as part of McLeod syndrome. This is an X-linked recessive phenotype characterized by a complete absence of XK cell surface proteins, and therefore markedly reduced expression of all Kell red blood cell antigens. For transfusion purposes, these patients are considered completely incompatible with all normal and K0/K0 donors.
- RP associated with autosomal recessive inheritance pattern is seen with Bardet–Biedl syndrome.[10]
Other conditions include
Acquired conditions resulting in ophthalmoscopic findings resembling RP include eye inflammation associated with infection in early age (rubella, syphilis, toxoplasmosis, herpesvirus), autoimmune paraneoplastic retinopathy, drug toxicity (phenothiazines and chloroquine, less commonly with Thioridazine and Hydroxychloroquine), diffuse unilateral subacute neuroretinitis and eye trauma. Acquired conditions may be unilateral or bilateral, and static or progressive.[11][12]
Genetics
Retinitis pigmentosa (RP) is one of the most common forms of inherited retinal degeneration.[13]
There are multiple
Over 100 mutations have been reported to date in the
Autosomal recessive inheritance patterns of RP have been identified in at least 45 genes.[15] This means that two unaffected individuals who are carriers of the same RP-inducing gene mutation in diallelic form can produce offspring with the RP phenotype. A mutation on the USH2A gene is known to cause 10-15% of a syndromic form of RP known as Usher's Syndrome when inherited in an autosomal recessive fashion.[23]
Mutations in four
The somatic, or X-linked inheritance patterns of RP are currently identified with the mutations of six genes, the most common occurring at specific loci in the RPGR and RP2 genes.[23]
Types include:
OMIM
|
Gene | Type |
---|---|---|
400004 | RPY | Retinitis pigmentosa Y-linked |
180100 | RP1 | Retinitis pigmentosa-1 |
312600 | RP2 | Retinitis pigmentosa-2 |
300029 | RPGR
|
Retinitis pigmentosa-3 |
608133 | PRPH2
|
Retinitis pigmentosa-7 |
180104 | RP9 | Retinitis pigmentosa-9 |
180105 | IMPDH1 | Retinitis pigmentosa-10 |
600138 | PRPF31 Inheritance can be either phenotypic or genotypic. | Retinitis pigmentosa-11 Autosomal Dominant |
600105 | CRB1 | Retinitis pigmentosa-12, autosomal recessive |
600059 | PRPF8 | Retinitis pigmentosa-13 |
600132 | TULP1 | Retinitis pigmentosa-14 |
600852 | CA4 | Retinitis pigmentosa-17 |
601414 | HPRPF3 | Retinitis pigmentosa-18 |
601718 | ABCA4 | Retinitis pigmentosa-19 |
602772 | EYS
|
Retinitis pigmentosa-25 |
608380 | CERKL | Retinitis pigmentosa-26 |
606068 | FAM161A | Retinitis pigmentosa-28 |
607921 | FSCN2 | Retinitis pigmentosa-30 |
609923 | TOPORS | Retinitis pigmentosa-31 |
610359 | SNRNP200
|
Retinitis pigmentosa 33 |
610282 | SEMA4A | Retinitis pigmentosa-35 |
610599 | PRCD | Retinitis pigmentosa-36 |
611131 | NR2E3
|
Retinitis pigmentosa-37 |
268000 | MERTK | Retinitis pigmentosa-38 |
268000 | USH2A | Retinitis pigmentosa-39 |
612095 | PROM1
|
Retinitis pigmentosa-41 |
612943 | KLHL7
|
Retinitis pigmentosa-42 |
268000 | CNGB1 | Retinitis pigmentosa-45 |
613194 | BEST1
|
Retinitis pigmentosa-50 |
613464 | TTC8 | Retinitis pigmentosa 51 |
613428 | C2orf71 | Retinitis pigmentosa 54 |
613575 | ARL6 | Retinitis pigmentosa 55 |
613617 | ZNF513 | Retinitis pigmentosa 58 |
613861 | DHDDS
|
Retinitis pigmentosa 59 |
613194 | BEST1
|
Retinitis pigmentosa, concentric |
608133 | PRPH2
|
Retinitis pigmentosa, digenic |
613341 | LRAT | Retinitis pigmentosa, juvenile |
268000 | SPATA7 | Retinitis pigmentosa, juvenile, autosomal recessive |
268000 | CRX | Retinitis pigmentosa, late-onset dominant |
300455 | RPGR
|
Retinitis pigmentosa, X-linked, and sinorespiratory infections, with or without deafness |
Pathophysiology
A variety of retinal molecular pathway defects have been matched to multiple known RP gene
Additionally, animal models suggest that the
Oxidative damage associated with lipid peroxidation is a potential cause of cone cell death in retinitis pigmentosa.[26]
Diagnosis
An accurate diagnosis of retinitis pigmentosa relies on the documentation of the progressive loss of photoreceptor cell function, confirmed by a combination of visual field and visual acuity tests, fundus and optical coherence imagery, and electroretinography (ERG).[27]
Visual field and acuity tests measure and compare the size of the patient's field of vision and the clarity of their visual perception with the standard visual measurements associated with healthy 20/20 vision. Clinical diagnostic features indicative of retinitis pigmentosa include a substantially small and progressively decreasing visual area in the visual field test, and compromised levels of clarity measured during the visual acuity test.[28] Additionally, optical tomography such as fundus and retinal (optical coherence) imagery provide further diagnostic tools when determining an RP diagnosis. Photographing the back of the dilated eye allows the confirmation of bone spicule accumulation in the fundus, which presents during the later stages of RP retinal degeneration. Combined with cross-sectional imagery of optical coherence tomography, which provides clues into photoreceptor thickness, retinal layer morphology, and retinal pigment epithelium physiology, fundus imagery can help determine the state of RP progression.[29]
While visual field and acuity test results combined with retinal imagery support the diagnosis of retinitis pigmentosa, additional testing is necessary to confirm other pathological features of this disease. Electroretinography (ERG) confirms the RP diagnosis by evaluating functional aspects associated with photoreceptor degeneration, and can detect physiological abnormalities before the initial manifestation of symptoms. An electrode lens is applied to the eye as photoreceptor response to varying degrees of quick light pulses is measured. Patients exhibiting the retinitis pigmentosa phenotype would show decreased or delayed electrical response in the rod photoreceptors, as well as possibly compromised cone photoreceptor cell response.
The patient's family history is also considered when determining a diagnosis due to the genetic mode of inheritance of retinitis pigmentosa. At least 35 different
- RLBP1 (autosomal recessive, Bothnia type RP)
- RP1 (autosomal dominant, RP1)
- RHO (autosomal dominant, RP4)
- RDS (autosomal dominant, RP7)
- PRPF8 (autosomal dominant, RP13)
- PRPF3 (autosomal dominant, RP18)
- CRB1 (autosomal recessive, RP12)
- ABCA4 (autosomal recessive, RP19)
- RPE65 (autosomal recessive, RP20)[30]
For all other genes (e.g. DHDDS), molecular genetic testing is available on a research basis only.
RP can be inherited in an
Genetic counseling depends on an accurate diagnosis, determination of the mode of inheritance in each family, and results of molecular genetic testing.
Treatment
There is currently no cure for retinitis pigmentosa, but the efficacy and safety of various prospective treatments are currently being evaluated. The efficiency of various supplements, such as vitamin A, DHA, NAC, and lutein, in delaying disease progression remains an unresolved, yet prospective treatment option.[32][33] Clinical trials investigating optic prosthetic devices, gene therapy mechanisms, and retinal sheet transplantations are active areas of study in the partial restoration of vision in retinitis pigmentosa patients.[34]
Stalling of disease
Studies have demonstrated the delay of rod photoreceptor degeneration by the daily intake of 15000
Bone marrow derived stem cells (BMSC)
MD Stem Cells, a clinical research company using autologous bone marrow derived stem cells (BMSC) in the treatment of retinal and optic nerve disease, published results from the Retinitis Pigmentosa cohort within their ongoing NIH registered Stem Cell Ophthalmology Study II (SCOTS2) clinical trial (NCT 03011541).[37] Outcomes were encouraging with 45.5% of eyes showing an average of 7.9 lines of improvement (40.9% LogMAR improvement over baseline) and 45.5% of eyes showing stable acuity over the follow-up. Results were statistically significant(p=0.016).[38] Retinitis Pigmentosa continues to be treated and evaluated in the study.
Argus retinal prosthesis
The Argus retinal prosthesis became the first approved treatment for the disease in February 2011, and is currently available in Germany, France, Italy, and the UK.[39] Interim results on 30 patients long term trials were published in 2012.[40] The Argus II retinal implant has also received market approval in the US.[41] The device may help adults with RP who have lost the ability to perceive shapes and movement to be more mobile and to perform day-to-day activities. In June 2013, twelve hospitals in the US announced they would soon accept consultation for patients with RP in preparation for the launch of Argus II later that year.[42][unreliable medical source?] The Alpha-IMS is a subretinal implant involving the surgical implantation of a small image-recording chip beneath the optic fovea. Measures of visual improvements from Alpha-IMS studies require the demonstration of the device's safety before proceeding with clinical trials and granting market approval.[43]
Gene therapy
The goal of
Drugs
This section needs expansion. You can help by adding to it. Find sources: "Retinitis pigmentosa Disulfiram" – news · newspapers · books · scholar · JSTOR (April 2022) |
One study at UC Berkeley found that disulfiram, a drug used to treat alcoholism in humans, had potential to partially restore vision loss in rats with retinitis pigmentosa, even during late stages of the disease.[46][47][48] Efforts to continue research in humans is ongoing.
Prognosis
The progressive nature of and lack of a definitive cure for retinitis pigmentosa contribute to the inevitably discouraging outlook for patients with this disease. While complete blindness is rare, the person's visual acuity and visual field will continue to decline as initial rod photoreceptor and later cone photoreceptor degradation proceeds.[49]
Studies indicate that children carrying the disease genotype benefit from presymptomatic counseling in order to prepare for the physical and social implications associated with progressive vision loss. While the psychological prognosis can be slightly alleviated with active counseling[50] the physical implications and progression of the disease depend largely on the age of initial symptom manifestation and the rate of photoreceptor degradation, rather than access to prospective treatments. Corrective visual aids and personalized vision therapy provided by Low Vision Specialists may help patients correct slight disturbances in visual acuity and optimize their remaining visual field. Support groups, vision insurance, and lifestyle therapy are additional useful tools for those managing progressive visual decline.[27]
Epidemiology
Retinitis pigmentosa is the leading cause of inherited blindness,[51] with approximately 1/4,000 individuals experiencing the non-syndromic form of their disease within their lifetime.[52] It is estimated that 1.5 million people worldwide are currently affected. Early onset RP occurs within the first few years of life and is typically associated with syndromic disease forms, while late onset RP emerges from early to mid-adulthood.
Autosomal dominant and recessive forms of retinitis pigmentosa affect both male and female populations equally; however, the less frequent X-linked form of the disease affects male recipients of the X-linked mutation, while females usually remain unaffected carriers of the RP trait. The X-linked forms of the disease are considered severe, and typically lead to complete blindness during later stages. In rare occasions, a dominant form of the X-linked gene mutation will affect both males and females equally.[53]
Due to the genetic inheritance patterns of RP, many isolate populations exhibit higher disease frequencies or increased prevalence of a specific RP mutation. Pre-existing or emerging mutations that contribute to rod photoreceptor degeneration in retinitis pigmentosa are passed down through familial lines; thus, allowing certain RP cases to be concentrated to specific geographical regions with an ancestral history of the disease. Several hereditary studies have been performed to determine the varying prevalence rates in Maine (USA), Birmingham (England), Switzerland (affects 1/7000), Denmark (affects 1/2500), and Norway.[54] Navajo Indians display an elevated rate of RP inheritance as well, which is estimated as affecting 1 in 1878 individuals. Despite the increased frequency of RP within specific familial lines, the disease is considered non-discriminatory and tends to equally affect all world populations.
Research
Future treatments may involve retinal
2012: Scientists at the University of Miami
2015: A study by Bakondi et al. at
2016: RetroSense Therapeutics aimed to inject viruses with DNA from light-sensitive algae into the eyes of several blind people (who have retinitis pigmentosa). If successful, they will be able to see in black and white.[63][64]
In 2017 the FDA approved the gene therapy voretigene neparvovec to treat people with biallelic RPE65 mutation-associated retinal dystrophy.[65]
In 2020, a literature review estimated the experimental therapeutic technique called transcorneal electrical stimulation as "probably effective" (level B) in retinitis pigmentosa, based on the evidence available at that time.[66]
In 2021 an optogenetics application of the protein Channelrhodopsin in a human patient was reported with partial recovery of non-functional vision in a series of one patient only. They did not use standard protocol to measure visual improvement, but created their own criteria.[67] The serendipitous discovery of the novel algal channelrhodopsin used came out of the 1000 Plant Genomes Project.[68]
Notable cases
- Jennifer L. Armentrout, American author of YA paranormal and Science Fiction
- Walt Bodine. American broadcaster, Kansas City
- Willie Brown, 41st Mayor of San Francisco, California
- Alex Bulmer, Canadian playwright[69]
- Molly Burke, Canadian YouTuber and motivational speaker
- Mark Erelli, American singer/songwriter, guitarist for Lori McKenna[70]
- Neil Fachie, British paralympic cyclist[71]
- William (Bill) Fulton, urban planner, author, and former Mayor of Ventura, California
- Gordon Gund, American businessman and professional sports team owner
- Rigo Tovar, Mexican musician, singer and actor
- Lindy Hou, Australian tandem cyclist and triathlete[72]
- Amar Latif, entrepreneur, television personality and professional traveller
- Rachael Leahcar, Australian singer/songwriter, actress and motivational speaker
- Steve Lonegan, Mayor of Bogota, New Jersey; Republican candidate for U.S. Senate[73]
- Chris McCausland, British stand-up comedian and actor
- Robin Millar, English record producer, musician and businessman[74]
- Woody Shaw, American jazz trumpeter[75]
- Regina Sorenson, Australian television personality[76]
- Shel Talmy, American record producer, songwriter and arranger[77]
- Sabriye Tenberken, German Tibetologist and developer of Tibetan Braille
- Dancing with the Stars contestant[78]
- Jon Wellner, American actor[79]
- Steve Wynn, American business magnate and Las Vegas casino developer[80]
- Sheena Iyengar, S.T. Lee Professor of Business in the Management Department at Columbia Business School[81]
See also
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