Non‐malignant lytic lesions of bone

Dear Editor, We report on the case of an 80-year-old woman with widespread lytic lesions throughout her skeleton which despite initial appearances were found to be non-malignant. The patient was admitted to the Rheumatology Department, Royal Derby Hospital, UK, with a 1month history of left knee pain and swelling which had become worse the previous day following a fall. For the preceding 3 years she had been undergoing monthly transfusions for myelofibrosis. Calcium pyrophosphate crystals were visualised on microscopy of knee aspirate. Pelvic X-ray, taken to exclude hip fracture, showed widespread small lytic lesions as well as two large cystic areas within the left proximal femur with cortical scalloping, although no fracture was present. The appearances were considered to be consistent with myeloma or metastases. Routine blood tests including calcium and alkaline phosphatase were unremarkable, protein electrophoresis and free light chain ratio were normal and chest X-ray showed no abnormality. All standard tumor markers were negative and a mammogram was normal. A computed tomography scan of chest, abdomen and pelvis was performed which detected focal discrete lytic lesions throughout the skeleton, on a background of osteosclerosis in keeping with her diagnosis of myelofibrosis (Fig. 1). A nuclear medicine bone scan demonstrated linear focal increased uptake in both the proximal left femoral diaphysis and the proximal right humerus, consistent with pathological fractures. Plain X-ray showed no fracture at either site. Following hematology review she underwent bone marrow aspiration and trephine. Histological examination of this demonstrated only grade IV myelofibrosis. There was no evidence of metastases. Given the severity of myelofibrosis demonstrated it was felt this could explain her widespread skeletal lucencies. The patient underwent prophylactic gamma nailing of a large lucency in her left femur. Bone biopsy of the site confirmed the absence of metastases. She was discharged with hematological follow-up. Myelofibrosis is a myeloproliferative disorder resulting in fibrotic replacement of the bone marrow, and the finding of discrete lytic lesions in patients with this as a sole diagnosis is extremely uncommon. Two studies published in the late 1950s to early 1960s documented the clinical and pathological findings in patients with myelofibrosis. The first looked at 110 patients with a primary diagnosis of myelofibrosis, excluding those with known malignancy. The X-ray films of these patients revealed mainly focal osteosclerotic changes, although normal findings or those of generalised increased density were also seen. The second, published in 1959, looked at 25 patients seen Figure 1 X-ray and computed tomography images of the patient’s pelvis. Arrows indicate multiple lytic lesions. International Journal of Rheumatic Diseases 2012; 15: e10–e11