Summary

Brown tumours are classic bony lesions that arise as a result of the effect of parathyroid hormone on bone tissue in some patients with hyperparathyroidism. They are erosive bony lesions caused by rapid osteolysis and peritrabecular fibrosis, resulting in a local destructive phenomenon. Facial skeleton is involved in about 2% of all cases of which the mandible is frequently affected. A 35-year-old female who was diagnosed with osteomalacia and brown tumour in posterior mandible as the sign of secondary hyperparathyroidism secondary to vitamin D deficiency is presented.