Elbow Knee Inflammatory Mystery

HISTORY: 51 y.o. female with end-stage renal disease on hemodialysis presents with left elbow pain and swelling. Presented to urgent care with sudden onset of pain for 1 week. She was afebrile and well-appearing. X-rays revealed elbow joint effusion with abnormalities in the radial head and coronoid process. Today, pain is constant, with a sharp quality localized to the posterior lateral aspect of her elbow. Notes weakness, swelling, and exacerbation of pain during gripping, lifting, and twisting. Ice, Tylenol, and Diclofenac gel 1% provided temporary relief. Denies trauma, recent infections, fevers/chills, history of gout, or morning stiffness. PHYSICAL EXAMINATION: Left elbow tenderness and swelling without overlying erythema. She cannot extend the elbow past 90° with pain upon pronation and supination. Left wrist with decreased range of motion and bony enlargement at the left radial ulnar joint. A large right knee effusion is also noted. DIFFERENTIAL DIAGNOSIS: 1. Secondary hyperparathyroidism2. Rheumatoid arthritis3. Gout4. Amyloid arthropathy5. Idiopathic inflammatory arthropathy. TEST AND RESULTS: Elbow 3-view XR:-Large elbow joint effusion with dysplastic appearance, including degeneration of radial head and coronoid process-Step-off of radial headUpper Extremity Joint MRI:-Large elbow effusion with peripheral low signal throughout joint-Chronic bony remodeling in ulnar trochlear and radiocapitellar joints with chronic appearing deformities in the wrist and shoulder-Impaction fracture of dorsal aspect of radial head appears chronicElbow arthrocentesis:-Negative culture, crystals-Gram Stain: No organisms.-Cell count: 1,737 nucleated cells, 60% lymphocytesKnee arthrocentesis:-74 k WBC with 98% neutrophils, negative culturesLabs:-PTH and Phos: 424 & 7.2 (H)-Sed Rate: 48 (H)-ANA: Negative; RF: <3.5; CCP Ab: Negative; CRP: 9.2-SPEP: Normal, serum-free kappa 29, lambda 16, ratio 1.8 -Uric acid: 6.9. FINAL/WORKING DIAGNOSIS: Idiopathic inflammatory arthropathy. TREATMENT AND OUTCOMES: 1.Steroid injection without relief2.Knee and elbow aspirations cultures were negative3.Consult with hematology who felt light chain skewing was due to ESRD4.Rheumatology considering DMARDs given sterile inflammation of right knee and elbow suggesting migratory inflammatory arthropathy