Clinical Characterization of Retinitis Pigmentosa Associated With Variants in SNRNP200.
Yusuf IH., Birtel J., Shanks ME., Clouston P., Downes SM., Charbel Issa P., MacLaren RE.
Importance: SNRNP200 is a recently identified genetic cause of autosomal dominant retinitis pigmentosa (RP). However, the associated retinal phenotype is not well characterized. Objective: To describe the retinal phenotype in patients with RP secondary to variants in SNRNP200. Design, Setting, and Participants: This retrospective, case-series study was performed at 2 tertiary referral centers for inherited retinal diseases. Participants included 9 consecutive patients from 8 families with RP attributed to variants in SNRNP200. Data were collected from August 2017 to March 2018 and analyzed from May to July 2018. Main Outcomes and Measures: Results of clinical evaluation, multimodal retinal imaging, and molecular genetic testing using targeted next-generation sequencing. Results: Of the 9 patients included in the analysis (4 female and 5 male; mean [SD] age at presentation, 19  years), each presented with nyctalopia, typically in the first 2 decades of life, although 2 patients experienced symptom onset in middle age. None had any consistent systemic features suggestive of syndromic RP. Retinal imaging studies and electroretinography findings were typical of a rod-predominant dystrophy with later involvement of cone photoreceptors. Phenotypic heterogeneity was typified by 4 unrelated patients with the common c.2041C>T SNRNP200 variant who demonstrated a variable age of disease onset (middle teenage years to the fourth decade of life). Disease progression was slow, with all but 1 patient maintaining visual acuity of better than 20/40 in the better-seeing eye in the fifth and sixth decades of life. Conclusions and Relevance: These data suggest that variants in SNRNP200 result in nonsyndromic RP with a typical phenotype of a rod-predominant dystrophy. Significant phenotypic heterogeneity and nonpenetrance were noted within some affected families. Symptom onset was typically within the first 2 decades of life, with slow progression and well-preserved visual acuities into the fifth and sixth decades.