COL9A2 and Stickler syndrome: Stickler syndrome is also inherited in an autosomal recessive manner caused by pathogenic variants in COL9A1, COL9A2, or COL9A3. The symptoms of Stickler syndrome include retinal detachment, auditory dysfunction, hypermobile tympanic membrane, and joint laxity (McAlinden et al., 2008; Acke et al., 2012).