Identification of Three Novel Homozygous Variants in COL9A3 Causing Autosomal Recessive Stickler Syndrome

Background Stickler syndrome (STL) is a rare, clinically and molecularly heterogeneous connective tissue disorder. Pathogenic variants occurring in a variety of genes cause STL, mainly inherited in an autosomal dominant fashion. Autosomal recessive STL is ultra-rare with only four families with biallelic COL9A3 variants reported to date. Results Here, we report three unrelated families clinically diagnosed with STL carrying different novel biallelic loss of function variants in COL9A3. Further, we have collected COL9A3 genotype-phenotype associations from the literature. Conclusion Our report substantially expands the molecular genetics and clinical basis of autosomal recessive STL and provides an overview about allelic COL9A3 disorders.