The importance of a differential diagnosis between true hemifacial microsomia and pseudo-hemifacial microsomia in the post-surgical long-term prognosis.

Long-term results after surgical treatment of the mandibular asymmetry in growing children with hemifacial microsomia (HFM), whether with osteotomies or distraction osteogenesis, have mostly shown a tendency towards the recurrence of the asymmetry. In contrast, in the literature we find sporadic case reports where the long-term post-surgical follow-up of patients diagnosed as HFM, are surprisingly stable. All these reports refer to patients who have substantially no soft tissue involvement, but only severe mandibular ramus and condyle deformities. The phenotypes of these cases are unexpectedly similar. The authors suggest, that it is possible that all of these cases might be isolated hemimandibular hypoplasias, misdiagnosed as HFM, which present a normal functional matrix and, therefore, tend to grow towards the original symmetry. Differential diagnosis between true HFM and this HFM-like isolated hemimandibular hypoplasia (pseudo-HFM) is of great importance given the very different prognosis and it is possible through the collaboration between not only surgeons and orthodontists, but also of geneticists and dysmorphologists.