623 - Chasing an Elusive and Complex Presentation of Severe Inflammatory Polyarthropathy.

Case Diagnosis: Pseudoseptic Arthritis and Transient Multifocal Tenosynovitis with extreme CRP and ESR Elevations Secondary to Seronegative Rheumatoid Arthritis.

Case Description: A 38-year-old male with a BMI of 46.0 and prior left knee meniscectomy presented with subacute painful right wrist swelling with elevated ESR (99 mm/h) and CRP (66 mm/L). MRI showed chronic tenosynovitis with peritendinous calcifications. Symptoms resolved without treatment. He presented months later with similar subacute painful left ankle swelling and MRI evidence of severe tenosynovitis of peroneus longus and brevis tendons. Within weeks, he developed painful right knee effusion, then left knee effusion, without constitutional symptoms. Laboratory workup showed persistently elevated ESR and CRP, thrombocythemia, mild anemia, and a positive Quantiferon testing. Knee joint aspirations to rule out septic or crystal arthritis were abnormal three times, with leukocytosis of 37000 and 75% polymorphonuclear cells. Aerobic, anaerobic, fungal and acid-fast bacilli cultures were negative. Left knee MRI revealed severe chronic synovitis with erosive disease. He was diagnosed with seronegative rheumatoid arthritis with eventual improvement in symptoms with Naproxen.

Discussions: Joint effusions with elevated CRP and ESR should raise concern for septic arthritis, with studies showing over 90% sensitivity with cutoff values of ≥15 mm/h for ESR and ≥20 mg/L for CRP. Extreme elevations of ESR and CRP with nonspecific clinical findings present a diagnostic challenge and have been correlated with malignancy (9%), infection (25%) and new onset rheumatological disorders (52%). In this case, the unusual imaging findings, severely elevated inflammatory markers, abnormal joint fluid analysis with otherwise unremarkable examination and negative rheumatological workup drove an extensive workup before the patient was successfully treated.

Conclusions: Extreme elevations of ESR and CRP should prompt evaluation for underlying malignancy or infection, especially in cases of seronegative rheumatological disease, which should be treated as diagnosis of exclusion.