Type A1 (BDA1), or Farabee‐type brachydactyly, results from heterozygous missense mutations in the signaling molecule Indian Hedgehog (IHH).[6] While homozygous inactivation of IHH leads to lethal chondrodysplasia, heterozygous mutations cause hypoplastic or absent middle phalanges.[7] Type B (BDB) is caused by truncating mutations in the receptor tyrosine kinase ROR. This evidence concerns the gene IHH and brachydactyly.