A form of frontootopalatodigital syndrome, characterized by deafness, cleft palate, and characteristic digital anomalies. OPD syndrome is divided into two forms based on severity: the milder form designated OPD type 1 (OPD1), and the more severe and often lethal form designated OPD type 2 (OPD2). OPD is an X-linked disorder. Two other genetic disorders with features overlapping OPD, frontometaphyseal dysplasia (FMD) and osteodysplasty, Melnick-Needles type (MNS) have been described; thus OPD1, OPD2, FMD, and MNS are allelic disorders.