Retinitis Punctata Albescens

Retinitis punctata albescens (RPA) is a rare, inherited eye disorder that affects the retina, the light-sensitive tissue at the back of the eye. It is a type of rod-cone dystrophy, meaning it primarily affects the photoreceptor cells responsible for vision in low light (rods) and color vision (cones). The condition gets its name from the characteristic appearance of numerous small, white or yellowish dots scattered across the retina, which can be seen during an eye exam. Patients with RPA typically first notice symptoms in childhood or early adulthood, most commonly night blindness (nyctalopia) and difficulty adjusting to dark environments. As the disease progresses, individuals may experience a gradual loss of peripheral (side) vision, leading to "tunnel vision." While central vision is often preserved for a longer period, it can eventually be affected, especially in more severe forms of the condition. It is important for patients to know that RPA is a progressive condition, meaning it worsens over time, although the rate of progression can vary significantly from person to person. Regular monitoring by an eye care specialist is crucial to manage symptoms and track the disease's progression. While there is currently no cure, ongoing research, including gene therapy trials, offers hope for future treatments.

Condition category: Retinal Dystrophy

Prevalence: 1 in 800,000

Inheritance patterns: Autosomal Recessive

Age of onset: Childhood

Clinical overview: Retinitis punctata albescens (RPA) is a rare, progressive, autosomal recessive rod-cone dystrophy that is considered an atypical or incomplete variant of retinitis pigmentosa (RP). It is clinically characterized by the presence of numerous discrete, small, white or yellowish punctate lesions scattered throughout the fundus, typically most dense in the mid-periphery and sparing the macula in early stages. These flecks are located at the level of the retinal pigment epithelium (RPE). The condition is primarily caused by biallelic mutations in the RLBP1 gene, which encodes the cellular retinaldehyde-binding protein (CRALBP), a key component of the visual cycle. Clinically, RPA presents with early-onset nyctalopia and delayed dark adaptation, followed by progressive constriction of the visual field and eventual decline in central visual acuity. Electroretinography (ERG) typically shows reduced or absent rod responses, with subsequent cone involvement. The disease shares phenotypic similarities with fundus albipunctatus (FA), a stationary night blindness disorder caused by RDH5 mutations, but RPA is distinguished by its progressive nature and more severe photoreceptor degeneration. Two severe subtypes of RLBP1-associated retinal dystrophy are recognized: Bothnia dystrophy (BD) and Newfoundland rod-cone dystrophy (NFRCD). BD is characterized by early macular atrophy occurring in the second or third decade of life, while NFRCD presents as a rapid form of rod-cone dystrophy leading to legal blindness during the third decade. The clinical course of classic RPA is generally slower, with longer preservation of macular function.

Patient and family guide: Retinitis punctata albescens (RPA) is a rare, inherited eye disorder that affects the retina, the light-sensitive tissue at the back of the eye. It is a type of rod-cone dystrophy, meaning it primarily affects the photoreceptor cells responsible for vision in low light (rods) and color vision (cones). The condition gets its name from the characteristic appearance of numerous small, white or yellowish dots scattered across the retina, which can be seen during an eye exam. Patients with RPA typically first notice symptoms in childhood or early adulthood, most commonly night blindness (nyctalopia) and difficulty adjusting to dark environments. As the disease progresses, individuals may experience a gradual loss of peripheral (side) vision, leading to "tunnel vision." While central vision is often preserved for a longer period, it can eventually be affected, especially in more severe forms of the condition. It is important for patients to know that RPA is a progressive condition, meaning it worsens over time, although the rate of progression can vary significantly from person to person. Regular monitoring by an eye care specialist is crucial to manage symptoms and track the disease's progression. While there is currently no cure, ongoing research, including gene therapy trials, offers hope for future treatments.

Symptoms and clinical features: The hallmark symptom of retinitis punctata albescens is early-onset nyctalopia (night blindness) and significantly delayed dark adaptation, often noticed in childhood. Patients struggle to see in low-light conditions or when transitioning from bright to dim environments. As the disease progresses, individuals experience a gradual loss of peripheral vision, leading to visual field constriction and "tunnel vision." Central vision and visual acuity are typically preserved in the early and middle stages of classic RPA but eventually decline in later stages. However, in severe subtypes like Bothnia dystrophy and Newfoundland rod-cone dystrophy, macular involvement and significant visual acuity loss occur much earlier, often in the second or third decade of life. Color vision may also be affected as cone photoreceptors degenerate.

Molecular pathology: Retinitis punctata albescens is primarily caused by biallelic mutations in the RLBP1 gene, located on chromosome 15q26.1. This gene encodes the cellular retinaldehyde-binding protein (CRALBP), a 36-kDa water-soluble protein expressed in the retinal pigment epithelium (RPE) and Müller glial cells. CRALBP plays a crucial role in the visual cycle, the biochemical pathway responsible for regenerating visual pigments after light exposure. In the RPE, CRALBP acts as a carrier protein for 11-cis-retinol and 11-cis-retinal. It binds to 11-cis-retinol, facilitating its oxidation to 11-cis-retinal by 11-cis-retinol dehydrogenase (RDH5), and protects these retinoids from isomerization. In Müller cells, CRALBP is involved in the cone-specific visual cycle, which is essential for maintaining cone photoreceptor function under daylight conditions. Mutations in RLBP1 lead to a deficiency or dysfunction of CRALBP, disrupting the visual cycle and impairing the regeneration of 11-cis-retinal. This results in delayed dark adaptation and night blindness. The accumulation of retinoid byproducts and the chronic stress on photoreceptors and RPE cells eventually lead to progressive retinal degeneration. The characteristic white dots seen in RPA are thought to represent accumulations of these retinoid byproducts or lipid deposits in the RPE.

Genetics: Retinitis punctata albescens is inherited in an autosomal recessive manner. This means that an affected individual must inherit two mutated copies of the causative gene, typically RLBP1, one from each parent. The parents of an affected individual are obligate carriers (heterozygotes) and are usually asymptomatic, although some carriers may exhibit subtle fundus changes or mild dark adaptation delays. Genetic counseling is essential for affected individuals and their families. The recurrence risk for siblings of an affected individual is 25%. Carrier testing for at-risk family members and prenatal diagnosis for pregnancies at increased risk are possible if the disease-causing mutations in the family have been identified. While RLBP1 is the primary gene associated with RPA, mutations in other genes, such as PRPH2, RHO, and RDH5, have occasionally been reported to cause similar flecked retina phenotypes, highlighting the genetic heterogeneity of these disorders. The penetrance of RLBP1 mutations is generally complete, but expressivity can vary significantly, even within the same family, ranging from classic RPA to the more severe Bothnia or Newfoundland rod-cone dystrophies.

Diagnostic evaluation: The diagnosis of retinitis punctata albescens is based on a combination of clinical findings, electrophysiology, imaging, and genetic testing. A comprehensive dilated fundus examination reveals the characteristic numerous, discrete, white or yellowish punctate lesions scattered across the retina, often sparing the macula initially. Full-field electroretinography (ERG) is crucial and typically demonstrates markedly reduced or absent rod responses, with cone responses becoming progressively attenuated over time. Dark adaptometry shows significantly delayed recovery of rod sensitivity. Optical coherence tomography (OCT) can reveal thinning of the outer retinal layers, loss of the ellipsoid zone, and sometimes cystic macular edema. Fundus autofluorescence (FAF) may show hyperautofluorescent spots corresponding to the white dots and areas of hypoautofluorescence indicating RPE atrophy. The diagnosis is confirmed by molecular genetic testing identifying biallelic pathogenic variants in the RLBP1 gene.

Differential diagnosis: Fundus Albipunctatus, Retinitis Pigmentosa, Bietti Crystalline Corneoretinal Dystrophy, Stargardt Disease, Familial Drusen, Vitamin A Deficiency

Natural history: The natural history of retinitis punctata albescens is characterized by a progressive decline in visual function. The disease typically begins with night blindness in childhood. During the first two decades of life, the fundus develops the characteristic white dots, and peripheral visual field loss begins. In classic RPA, central vision is often maintained into middle age, but progressive RPE and photoreceptor atrophy eventually lead to significant visual impairment. The white dots may fade or disappear in advanced stages, replaced by widespread chorioretinal atrophy and pigmentary changes typical of retinitis pigmentosa. In the more severe Bothnia and Newfoundland subtypes, the progression is accelerated, with early macular atrophy leading to legal blindness by the third or fourth decade of life.

Management and treatment research: ### Current Management There is currently no cure for retinitis punctata albescens (RPA). Care focuses on monitoring retinal health, treating complications when possible, and supporting independence and quality of life. - **Regular retinal follow-up:** An inherited retinal disease specialist may monitor vision and retinal changes with visual acuity and visual field testing, optical coherence tomography (OCT), and retinal photographs or other imaging. OCT uses light waves to create detailed images of the retina. - **Genetic testing and counseling:** RPA is commonly associated with disease-causing variants in visual-cycle genes, including *RLBP1* and *RDH5*. Genetic testing can help confirm the diagnosis, clarify inheritance in a family, and identify appropriate research or registry opportunities. - **Low-vision rehabilitation:** Magnifiers, electronic reading devices, glare-control lenses, improved lighting, orientation and mobility training, and school or workplace accommodations may help people make the best use of remaining vision. - **Management of complications:** Some people with inherited retinal degeneration develop cystoid macular edema (CME), a buildup of fluid in the macula, the central area of the retina used for detailed vision. When CME is present, carbonic anhydrase inhibitors, such as topical dorzolamide or oral acetazolamide, may be considered. Cataracts and other eye conditions should also be evaluated and treated as appropriate. Night blindness and slow dark adaptation are common in RPA. Allowing extra time for the eyes to adjust when moving between bright and dim settings, using appropriate lighting, and planning for low-light environments may be helpful. ### Approved Therapies There are no FDA-approved treatments specifically for retinitis punctata albescens, including RPA caused by *RLBP1* or *RDH5* variants. ### Investigational Therapies There are no condition-specific interventional therapies currently listed in the treatment pipeline for retinitis punctata albescens. Research in inherited retinal diseases includes gene-based approaches, medicines intended to support retinal function, and cell-based therapies. However, treatments studied for other inherited retinal diseases should not be assumed to be appropriate or effective for RPA. Future research eligibility may depend on the disease-causing gene, retinal disease stage, and a study’s specific enrollment criteria. ### Clinical Trial Participation People with RPA may be eligible for observational research studies or patient registries. The **Inherited Retinal Degenerative Disease Registry** (**NCT02435940**) is recruiting and is sponsored by the Foundation Fighting Blindness. Registries collect clinical, genetic, and vision information to help researchers better understand inherited retinal diseases and how they change over time. Participation may also help individuals learn about future research opportunities. An inherited retinal disease specialist or genetic counselor can help patients and families discuss genetic testing and research participation.

Outlook: The visual prognosis for retinitis punctata albescens varies depending on the specific genetic mutation and subtype. Classic RPA generally has a slower progression, with patients often retaining useful central vision into middle age or later. However, the severe Bothnia and Newfoundland subtypes carry a much poorer prognosis, with early macular involvement leading to legal blindness by the second or third decade of life. Overall quality of life is impacted by the progressive loss of night and peripheral vision.

Epidemiology: Retinitis punctata albescens is a very rare disorder. It accounts for approximately 1% of all patients with autosomal recessive rod-cone dystrophies. The condition occurs worldwide, but certain severe subtypes have specific geographic concentrations due to founder effects. Bothnia dystrophy is highly prevalent in the Bothnia region of northern Sweden, while Newfoundland rod-cone dystrophy is concentrated in Newfoundland, Canada.

Selected references: 1. Bocquet B, et al. Retinitis Punctata Albescens and RLBP1-Allied Phenotypes: Phenotype-Genotype Correlation and Natural History in the Aim of Gene Therapy. Ophthalmol Sci. 2021;1(3):100052. 2. Burstedt M, et al. Retinal dystrophy associated with RLBP1 retinitis pigmentosa: A 5-year prospective natural history study. Invest Ophthalmol Vis Sci. 2023;64:42. 3. Choi VW, et al. AAV-mediated RLBP1 gene therapy improves the rate of dark adaptation in Rlbp1 knockout mice. Mol Ther Methods Clin Dev. 2015;2:15022. 4. Espinosa-Barberi G, et al. A multimodal study and management of retinitis punctata albescens. Rom J Ophthalmol. 2020;64(2):213-216. 5. Interim safety and efficacy of gene therapy for RLBP1-associated retinitis punctata albescens. Nat Commun. 2024;15:7915.