A novel single-base deletion in ROR2 causes atypical brachydactyly type B1 with cutaneous syndactyly in a large Chinese family.

Mutations in ROR2, encoding the receptor tyrosine kinase-like orphan receptor 2, cause two distinct skeletal diseases: autosomal dominant brachydactyly type B1 (BDB1) and autosomal recessive Robinow syndrome. In a large Chinese family with a limb phenotype, consisting of atypical BDB1 and cutaneous syndactyly of varying degrees, we performed a two-point linkage analysis using microsatellite markers on 2q33-q37 and 9q22.31, and found a significant linkage to the ROR2 locus. We identified a novel single-base deletion in ROR2, c.2243delC (p.W749fsX24), and confirmed its segregation with the limb phenotype in the family. This deletion is predicted to produce a truncated ROR2 protein with an additional C-terminal polypeptide of 24 amino-acid residues. To the best of our knowledge, the deletion represents the second ROR2 mutation associated with a BDB1-syndactyly phenotype.