The case of a 17-month-old boy with symmetric involvement of both femora in chronic recurrent multifocal osteomyelitis (CRMO) is presented. Imaging showed an extraordinary involvement of both femoral diaphyses and distal metaphyses with extensive lamellar-like periosteal reactions. Diagnosis was based upon laboratory tests, bone scintigraphy, and MRI findings and was proved by open bone biopsy. SYMMETRIC INVOLVEMENT of extremity bones in chronic recurrent multifocal osteomyelitis (CRMO) is rare and is documented in the literature in several case reports (1-3). The first case was published by Giedion et al (1) in 1972. Both femoral metaphyses were involved in a nine-year-old girl. In 1974, Gustavson and Wilbrand (3) published another case of symmetric chronic osteomyelitis of the distal femora in a seven-year-old girl. Two further cases of bilateral symmetric CRMO of the femoral metaphyses, in a four-year-old girl and in an eight-year-old boy, were published by Brown and Wilkinson in 1988 (13). Whereas periosteal changes were mild in these cases, Schenk et al (4) reported progressive hyperostosis with osteolytic areas in another case of CRMO with unilateral femoral involvement. We describe the imaging findings of a symmetric involvement of both femora in CRMO with extensive periosteal changes and osteolyses.
CASE REPORTA 17-month-old boy was admitted to hospital after a four week episode of weakness, inappetence, and weight loss. Eventually, he refused to walk. Ultrasonography of the hip and knee joints was normal. Laboratory tests showed a white blood cell count of 16,800/ mm 3 , a C-reactive protein of 99 mg/liter, and an erythrocyte sedimentation rate (ESR) of 75 mm, indicating an inflammatory process. Elevated serum alkaline phosphatase of 435 U/liter pointed to a process at the skeletal system. Bone scintigraphy with 99m Technetium-labeled methylene diphosphonate showed multiple abnormal foci of increased calcium turnover. The main finding was a symmetrically increased radiotracer uptake in the diaphyses of both femora (Fig. 1a). In addition, several ribs showed a mildly increased activity (Fig. 1b). Radiographs were obtained and extensive concentric solid periosteal new bone formation at both femoral diaphyses with a few small osteolytic zones were discovered (Fig. 2a). The third to sixth rib on the right side were deformed and sclerotic (Fig. 2b). Based on these findings, multifocal chronic osteomyelitis was presumed.As differential diagnoses, neoplastic diseases such as histiocytosis X or leukemia, and metastatic disease from Ewing sarcoma or neuroblastoma were considered. Ultrasonography of the abdomen and bone marrow biopsy gave no further evidence of malignant disease.For further assessment of the femoral lesions, MRI was performed on a 1.5-Tesla scanner (Magnetom Symphony; Siemens, Erlangen, Germany).Transverse T2-weighted (TR ϭ 3800 msec, TE ϭ 90 msec), T1-weighted (TR ϭ 560 msec, TE ϭ 12 msec), and T1-weighted images after intravenous (i.v.) injection of 0.1 mmol/kg of gadodiamide (Omniscan; Nycome...