Pseudoseptic Arthritis: An Initial Presentation of Underlying Psoriatic Arthritis.

Pseudoseptic arthritis is an acute inflammatory monoarthritis that clinically mimics septic arthritis. We encountered an 86-year-old male with a past medical history of hypertension, type 2 diabetes mellitus, and chronic kidney disease (CKD) stage 3 who presented in the emergency department with acute onset of severe left knee joint pain and was started on antibiotics for suspected septic arthritis. Septic arthritis was ruled out with negative synovial fluid culture. Timely initiation of steroids rapidly improved his condition, and he was discharged in stable condition on the 7th day of admission. Though pseudoseptic arthritis has been reported in a variety of settings including rheumatoid arthritis, ankylosing spondylitis, and medication such as intraarticular hyaluronic acid injection, our case report presents a case of pseudoseptic arthritis as the initial presentation of undiagnosed psoriatic arthritis.