XYLT2 and retinal detachment: Joint contractures are only reported in B3GALT6 and B3GAT3 mutations, whereas multiple fractures due to bone fragility are commonly found in patients harbouring B3GALT6 and XYLT2 mutations and to a lesser extent in mutations in B3GAT3, B3GALT7 and B4GALT7. Cardiac defects, including septal defects and valve defects, are associated with mutations in XYLT2, B3GAT3 and, to a lesser extend, B3GALT6. Ocular involvement is present in most reported patients with XYLT2(cataract and retinal detachment) and B4GALT7 mutations and is a rare and variable finding in B3GAT3 mutations.