A brachydactyly characterized by autosomal dominant inheritance of malformations of the middle phalanx of the index finger and anomalies of the second toe that has_material_basis_in heterozygous mutation in the BMPR1B gene on chromosome 4q or in the GDF5 gene on chromosome 20q11 or heterozygous duplication in a regulatory element of BMP2 on chromosome 20p12. [ http://purl.obolibrary.org/obo/ECO_0007645 ]