抄録
A case of focal osteoporotic bone marrow defects (FOBMDs) with a simple bone cyst-like change arising in the bilateral anterior maxilla of a 9-year-old Japanese boy is reported. Two FOBMD lesions were simultaneously found by chance as small oval-shaped unilocular radiolucencies symmetrically located between the canines and lateral incisors on a panorama radiograph during dental treatment of the patient's right maxillary canine, which erupted obliquely as the canine tooth roots were laterally displaced by the lesions. The lesions were surgically extirpated under a clinical diagnosis of developmental jaw cysts. However, they were shown at surgery not to be cysts but instead bone-marrow-like tissues, though the right lesion contained a cavity space within it. Histopathologically, they were fatty marrow without hematopoiesis, and irregularly-shaped bony trabeculae and blood clots were seen scattered throughout the marrow. They were diagnosed as FOBMD (left) or FOBMD with simple bone cyst (right), although they did not contain hematopoietic marrows. Thus, their fully fatty change with some blood pools suggests that they were in the initial stage of developing into simple bone cysts. Based on these histological observations, we propose a new hypothesis of FOBMD as one of the histopathogenetic precursors of simple bone cyst.
