A 4-year-old boy with pain in his left shoulder.

Abstract

Apreviously healthy 4-year-old boy presented with left shoulder pain. Two nights prior to admission he was sleeping in bed with his grandmother and awoke complaining that his left arm hurt. Although he went to school the next day, he left early due to arm pain caused by trying to put on his jacket. That night, he couldn’t sleep due to persistent fever and pain, so he was taken to an emergency department. His past history is unremarkable. Family history and development were normal; immunizations were up-to-date. On presentation he was afebrile. His growth parameters were normal. He was alert and he was crying during the examination. His general physical examination was normal. His right arm was normal. The left arm was held flexed at the elbow and kept rigid. His clavicles were intact. He had mild fullness or edema of the left anterior shoulder compared to the right. He was tender to palpation over the left anterior shoulder without warmth or erythema. He moved his wrist and all his fingers without pain. Distal pulses were normal. Neurologic examination was normal. The initial laboratory evaluation was hemoglobin 11.8 g/dL, white blood cell count 12,000/mm3 with 72% neutrophils, and platelet count 450,000/mm3. Erythrocyte sedimentation rate (ESR) was 94 mm/hour and Creactive protein (CRP) was 4.3 mg/dL. His shoulder X-ray was normal. Ultrasonography revealed left shoulder joint effusion with internal debris with a volume of roughly 4 cm3. The joint effusion was predominantly located posteriorly. There was mild hyperemia of the surrounding tissues. Aspiration of the shoulder joint performed by interventional radiology yielded 4 cm3 of turbid fluid with white blood cell count of 200,000/mm3 with 98% neutrophils. Ultimately, both the joint culture, and subsequently a blood culture from the outside hospital, grew methicillin-sensitive Staphylococcus aureus (MSSA). Magnetic resonance imaging performed 3 days later showed findings suggestive of left septic joint with small effusion and synovitis and marrow edema with enhancement involving the epiphysis of the proximal right humerus concerning for osteomyelitis. A peripherally inserted central catheter was placed and he started receiving intravenous cefazolin every 8 hours to be given for 4 to 6 weeks. Robert Listernick, MD, moderator: Why would this child have osteomyelitis of the shoulder? This seems like an unusual location. Larry Kociolek, MD, pediatric infectious diseases physician: Hematogenous osteomyelitis usually presents in the metaphysis of long bones, in this case the humerus, because blood flow is highest at the ends of long bones. Osteomyelitis contiguous to joints in young children often ruptures into the joint leading to a secondary septic arthritis. This is much more likely the case than having a primary septic arthritis lead to secondary osteomyelitis. Dr. Listernick: OK, now I can ask a question that has been bugging me for a long time. Why does everyone seem to order both ESR and CRP when looking for inflammatory processes, one of which would be a bone or joint infection? Dr. Kociolek: Simultaneous use of both ESR and CRP is helpful for monitoring treatment response in bone and joint infections, which may not be the case in other infectious and inflammatory conditions. In bone and joint infections, CRP rises early and declines with the resolution of infection, whereas ESR tends to resolve more slowly. Normalization of CRP is an excellent marker of initial response to therapy in osteomyelitis. Some physicians use normalization of ESR to guide long-term response to Robert Listernick, MD, is an Attending Physician, Ann & Robert H. Lurie Children’s Hospital of Chicago; and a Professor of Pediatrics, Northwestern University, Feinberg School of Medicine, Division of Academic General Pediatrics. Address correspondence to Robert Listernick, MD, via email: pedann@Healio.com.