BMPR1B and Acromesomelic dysplasia, Grebe type: While the number of affected individuals with ACD due to BMPR1B mutations is small, our previous [9] and present results indicate a possible genotype-phenotype correlation according to which BMPR1B mutations with a strong functional effect would cause Grebe syndrome, while milder mutations would result in the clinically and radiologically milder du Pan dysplasia.