Unusual location of eosinophilic granuloma

Eosinophilic granuloma EG is a benign self-limiting disease, which belongs to the spectrum of Langerhans' cell histiocytosis LCH. The etiology of LCH remains unknown, although the evidence indicates that it is a clonal proliferative disorder of Langerhans cells, it has also been characterized as reactive disorder, neoplastic process and a berrant immune response. Eosinophilic granuloma is characterized by single or multiple skeletal lesions occurring predominately in children, adolescents and young adults, it accounts for 70% of LCH. It is more common in males, and the common sites are the skull, mandible, ribs, spines and long bones particularly the femur and the humerus. The estimated incidence of EG is 3-4 per million of the population. Vertebral bone involvement is rarely seen and usually affects the vertebral body. We are reporting an unusual case of EG in a female child presented with a solitary lesion at posterior element of lumbar vertebra.