MAP2K1 and melorheostosis: Patients who have sporadic melorheostosis are a distinct group and do not have germline6, 33, or as we now show, somatic mutations in LEMD3. It remains to be seen if the radiographic similarities in melorheostosis caused by LEMD3 mutations and MAP2K1 mutations are due to involvement of a common pathway with activation of SMADs, or are simply a similar clinical outcome.