Tennis racquets in the jaw: eosinophilic granuloma

A healthy 4-year-old boy presented with a 4 month history of episodic pain and swelling of his left jaw which appeared to respond to antibiotics. An ultrasound, orthopantomogram (OPG), CT scan and MRI revealed a 3 cm well circumscribed lesion in the left mandible near, but not related to, his posterior molar teeth. The radiological differential diagnosis included a mandibular abscess or neoplasm such as Ewing's sarcoma, or Langerhans cell histiocytosis (LCH). A fine needle aspirate (FNA) was performed. The cytology, in conjunction with the immunohistochemistry (S100 protein and CD1a expression by the histiocyte-like cells) and electron microscopy (demonstrating Birbeck bodies) showed features characteristic of LCH. The boy was treated with an intra-lesional injection of methyl prednisolone with radiological and clinical evidence of regression of the lesion. Localised LCH is also known as eosinophilic granuloma (EG). Its pathogenesis is unknown, although recent studies suggest it is a disease that results from mononuclear phagocyte dysregulation that may be infective, autoimmune or neoplastic in origin. EG is rare, usually affecting children 5-15 years. The jaws are affected in 10-20% of cases with mandible involvement more common in adults. No consensus exists for the optimal therapy which includes curettage, intra-lesional prednisolone and chemotherapy.