Retinal detachment in Type IX collagen recessive Stickler syndrome.

Objective: Stickler Syndrome (SS) is associated with eye, joint and orofacial abnormalities. Most cases are dominantly inherited through COL2A1/COL11A1 variants encoding type-II/XI collagen, with patients having up to 78% retinal detachment (RD) risk. Rarer cases of recessive SS have also been identified, associated with pathogenic variants of genes including COL9A1, COL9A2 & COL9A3 encoding type-IX collagen, but there is limited published data on patients' phenotype or RD risk. Our study aimed to investigate RD risk in type-IX recessive SS, determining whether patients would benefit from prophylactic retinopexy. A secondary objective was to explore patient phenotypes, identifying key features which clinicians should identify, leading to earlier diagnosis.

Methods: We report 13 cases from 11 families with Type-IX recessive SS, identified from the cohort attending the NHS England Highly Specialised Stickler Syndrome Service (1/1/15-31/12/22). Patients underwent multidisciplinary assessment by ophthalmology, rheumatology and audiology.

Results: 6/11 families exhibited previously undescribed genetic variants, and 7 had consanguineous parents. Clinical findings included abnormal vitreous architecture and high myopia. 15.4% of patients developed RD secondary to horseshoe retinal tears, with no cases of bilateral RD or giant retinal tears (GRTs). No patients had cleft palate, and 30.8% had midfacial hypoplasia. Hearing loss was more prevalent (91.7%) than in dominant SS. Arthropathy was uncommon but variable in manifestation.

Conclusions: Ours results do not point to high RD nor GRT incidence in recessive SS, although given the rarity, our numbers are small. Prophylactic retinopexy should only be offered case-by-case for fellow eyes of patients presenting with GRT detachments in their first eye.