TDO syndrome (Online Mendelian Human Genetics (OMIM) database 190320) is caused by DLX3 mutations, and the c.571_574delGGGG mutation in DLX3 (MT-DLX3) is the most common etiologic mutation of TDO (Price et al., 1998a; Price et al., 1998b). Here, DLX3 is linked to tricho-dento-osseous syndrome.