In two probands with STL1, a substitution in the X-position of the Gly-XY triplet was found: c.2710C>T (p.Arg904Cys); in a proband with CD, a substitution in the Y-position was found: c.823C>T (p.Arg275Cys), and, in a proband with SED tarda, similar to the mild form of Morquio A syndrome described earlier by Girisha K.M. et al., [26] variant c.3397C>T (p.Arg1133Cys) was found. Here, COL2A1 is linked to mucopolysaccharidosis type 4A.