Spondylo-Megaepiphyseal-Metaphyseal Dysplasia, also known as smmd, is related to metaphyseal dysplasia and cleidocranial dysplasia 1. An important gene associated with Spondylo-Megaepiphyseal-Metaphyseal Dysplasia is NKX3-2 (NK3 Homeobox 2). Affiliated tissues include bone, and related phenotypes are short neck and disproportionate short-trunk short stature