SOX9 and Stickler syndrome: The three main genetic causes of syndromic PRS are SOX9 variants, chromosome 22q11 deletion and Stickler syndrome.7 Stickler syndrome is commonly caused by variants in the COL2A1 or COL11A1 genes, where ophthalmic complications, such as retinal detachment and blindness, may be seen; the retinal detachment can be prevented by retinopexy in those with a fragile retina.