Your Diagnosis, Please
A previously healthy 1-year-old Hispanic female presented to her pediatrician with left wrist swelling of several days. She was afebrile and did not have any tenderness nor did the swelling limit her range of motion. A plain radiograph of the left wrist demonstrated a lytic lesion at the distal ulnar diaphysis with prominent periosteal reaction and cortical destruction. As a result, she was referred to a pediatric oncologist. At the visit, there was mild induration over the dorsal surface of left wrist without erythema or tenderness. She remained afebrile and demonstrated full range of motion of left hand and wrist.
Laboratory studies during the oncology visit were as follows. A complete blood count yielded a hematocrit of 36.4%, a white blood count of 18 × 103/mm3 with 15% neutrophils, 79% lymphocytes, 5% monocytes and 1% eosinophils and a platelet count of 442 × 103/mm3. Erythrocyte sedimentation rate was 38 mm/h. Magnetic resonance imaging of the wrist revealed an osteolytic lesion in the distal ulnar diaphysis which measured 1.0 cm × 1.2 cm × 2.1 cm. There was cortical destruction with smooth appearing periosteal reaction. The lesion demonstrated diffuse T2 hyperintensity and contrast enhancement that extended along the proximal aspect of the ulna and deep into the periosteum. Because of the concern for an oncologic process, a biopsy of the distal ulna was conducted, and the pathology findings showed reactive bone tissue with patchy chronic inflammation compatible with osteomyelitis. There were no cultures performed on the biopsy sample. Blood cultures and Coccidioides serology by enzyme immunoassay were negative. Empiric oral clindamycin was initiated. After 20 days of clindamycin, the parents noticed that the left wrist swelling had increased. Therefore, the child was hospitalized. Upon admission, she had a temperature of 36.4°C, pulse of 130 beats/min, respiratory rate of 24 breaths/min and blood pressure of 102/66 mm Hg with her weight and height at the 18th and 13th percentiles, respectively. The left wrist was edematous and mildly tender, and there was a nondraining central pustule with surrounding erythema. A complete blood count showed a hematocrit of 38.5%, a white blood count of 14.6 × 103/mm3 and a platelet count of 312 × 103/mm3. Magnetic resonance imaging revealed an increase in the size of the distal ulnar lesion, now measuring 1.6 cm × 1.7 cm × 2.5 cm, and an interval development of a bony defect within the dorsal aspect of the ulnar diaphysis. In addition, there was T2 hyperintense material extending through this defect into the adjacent soft tissues and to the level of the skin surface (Fig. 1). Debridement of the ulnar lesion was performed. Intraoperative findings showed a significant collection of purulent material within the subcutaneous region as well as a large cortical defect and an intramedullary abscess in the distal ulna. Specific laboratory tests eventually revealed the diagnosis.