Ankylosing Spondylitis Presenting with Asymmetrical Arthritis and Fever of Unknown Origin

A 19 yrs male presented with 3-4 months history of intermittent fever; 2 months history of right knee joint pain and swelling. He also had history of lower back pain and reduced lumbar mobility since last 8-10 months. Radiographs of thoracic and lumbar spine shows marginal syndesmophytes with bamboo like appearance and pelvic radiographs showed inflammation in right sacroiliac joint s/o sacroilitis. He was diagnosed with ankylosing spondylitis based on limitation in lumbar spine mobility, limitation in chest expansion, radiographic findings and HLA B27 report. This case highlights that asymmetrical arthritis and fever of unknown origin can be initial presentation of ankylosing spondylitis.