COL2A1 and metabolic disease: Among these, Stickler syndromes (14.8%: COL2A1 (5.6%), COL2A1-associated Kniest dysplasia (3.7%), COL11A1 (5.6%)) were the most prevalent entities, underlying metabolic diseases were found in 9.4% (OAT, HADHA, MMACHD, PMM2), 5.3% had syndromic features of phenotypic albinism (HPS5, HPS6, LYS), and 3.8% were mitochondriopathies.