Hemophiliac pseudotumor

Pseudotumors are an uncommon complication of hemophilia, occurring in 1%–2% of persons with severe forms of the disease. A hemophilic pseudotumor is an encapsulated, chronic, slowly expanding hematoma seen in patients with a severe coagulation disorder. Many patients recall sustaining an injury prior to development of the pseudotumor. These lesions usually occur in soft tissues (often intramuscular) but occasionally occur de novo in bone or in a subperiosteal location. Pseudotumors that occur in muscles with broad tendon insertions readily progress to cause severe pressure erosion of adjacent bone. The bones most commonly involved by pseudotumors are the femur, pelvis, tibia, and bones of the hand. Osseous pseudotumors have a variable radiographic appearance but demonstrate some common features. Osseous pseudotumors are lytic in nature and usually have a well-defined margin; however, they may become quite extensive and completely replace segments of bone, as in this case. Lesions may be intramedullary or eccentric in location and are often expansile. Osseous trabeculae frequently traverse the lesions.