A case of conversion disorder presenting as chronic trismus.

Trismus can be the symptom of several diseases. For the most part, the inability to open the mouth is due to an articular disorder but occasionally, the cause may be extra-articular. In this case, being reported, non-articular hysterical trismus caused the jaw to lock in an 11-year-old boy for 3 months. During this period the jaw was completely locked and the locking was associated with moderate to severe pain. After three sessions of therapy the patient was able to open his mouth 33 mm and his eating was back to normal. Conversion disorders often present with dramatic physical presentation including trismus and jaw lock. This report highlights the importance of complete history taking and a thorough clinical examination to make a correct diagnosis in a patient with trismus.