An 11-year-old girl is brought to the emergency department due to right shoulder pain. The patient first noticed the pain 4 days ago after softball practice. She has been placing cold compresses over the shoulder and taking acetaminophen with initial improvement, but the pain has awakened her from sleep the last 2 nights. Today she is unable to lift her right arm to brush her teeth. Four months ago, the patient was diagnosed with polyarticular juvenile idiopathic arthritis involving the wrists, knees, and ankles. She is taking methotrexate, and her symptoms had been gradually improving after dose adjustments. Temperature is 38.5 C (101.3 F). The patient holds her right arm at her side, and she resists attempts to move the shoulder due to pain. The overlying skin is warm. Bilateral wrists, knees, and ankles are mildly edematous. The shoulder joint is aspirated, and synovial fluid analysis reveals leukocyte count of 55,000 cells/mm³, with 80% polymorphonuclear cells and 20% lymphocytes. Which of the following is the best next step in management of this patient?

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11ec25c8_d743_e34d_bc81_177da0f273d9_MD0003_00 This patient's history and synovial fluid analysis are indicative of septic arthritis, a bacterial joint infection. Juvenile idiopathic arthritis (JIA) is a risk factor for septic arthritis because underlying joint inflammation predisposes to bacterial seeding. In addition, patients with JIA often require treatment with immunosuppressants, as in this case, thereby increasing susceptibility to unusual pathogens. JIA management may also include intra-articular injections, which potentially allow direct inoculation of the joint space. Recognition of septic arthritis is frequently delayed in patients with JIA because new onset joint swelling may be attributed to a JIA flare. However, an atypical flare of a single joint should raise suspicion for an infectious etiology. Red flags include severe, acute pain, often leading to nighttime awakening and refusal to move the affected joint, as seen in this patient. Fever is also typically present. Joint aspiration should be performed for suspected septic arthritis. Elevated synovial leukocyte count >50,000/mm³ with a neutrophil predominance (polymorphonuclear cells >80%-90%) is highly suggestive of infection, and identification of bacteria in the synovial fluid is diagnostic. Treatment includes immediate antibiotic therapy to prevent permanent joint damage. (Choices A, B, and D) Adding a biologic disease-modifying antirheumatic drug, increasing methotrexate dose, and administering intra-articular glucocorticoids are JIA treatment options. A JIA flare typically presents with insidious onset of intermittent joint pain, swelling, and morning stiffness. In addition, synovial leukocyte count during a JIA flare is typically <50,000/mm³. This patient's acute onset of severe, worsening pain causing nighttime awakening and synovial fluid analysis are concerning for septic arthritis. (Choice E) Nonsteroidal anti-inflammatory drugs and rest are treatments for musculoskeletal injuries (eg, rotator cuff tendinitis/bursitis), which typically present with pain exacerbated by shoulder movement. Severe pain with nighttime awakening, fever, and elevated synovial leukocyte count would not be expected. Educational objective: In patients with juvenile idiopathic arthritis who have an atypical flare of a single joint, such as severe pain with nighttime awakening, septic arthritis should be considered. An elevated synovial leukocyte count >50,000/mm³ with a neutrophil predominance supports the diagnosis. Treatment is immediate antibiotic therapy. References: Arthritis in children: comparison of clinical and biological characteristics of septic arthritis and juvenile idiopathic arthritis. (http://www.ncbi.nlm.nih.gov/pubmed/27655660) Complications of treatments for pediatric rheumatic diseases. (http://www.ncbi.nlm.nih.gov/pubmed/30031500)

An 11-Year-Old Girl Is Brought to the Emergency Department Due