RESUMO
Masseter traumatic myositis chondro-ossificans (TMCO) is a rare pathological condition that causes severe mandibular function restriction. The aim of the present study is to report a TMCO case after direct masseter muscle injury and correlate it to bone and cartilage biomarkers up-regulation. Caucasian male patient, 38 years old, seeks treatment nine days after trauma with severe mouth opening limitation. Physical examination revealed a circumscribed hardened area connected to masseter muscle on the left side. Cone beam tomography and ultrasonography of masseter region were requested. There was incomplete fracture between the posterior board of inferior jaw and coronoid process as well as calcification within masseter muscle. The proposed treatment was excisional biopsy of calcification, coronoid process removal to enhance mouth opening as well as incomplete condyle fracture monitoring. Material removed was sent for histological analysis in order to confirm diagnosis. Immuhistochemistry was conducted and it was found that chondro-ossification biomarkers such as TGF-b1, Indian Hegdehog (IHH), BMP2, osteopontin (OP) and osteocalcin (OC) were up-regulated. One-year follow-up showed that the patient is stable with increased mouth opening and satisfactory jaw movements. Pathologists and maxillofacial surgeons must be aware of differential diagnosis of TMCO. Understanding cellular mechanisms of muscle tissue after trauma is also important once cellular pathway modifications leads to clinical features that differ from previously described in literature.