29th April 2024

A 30-year-old man presents with a 2-year history of lower back pain, which is worse in the morning and improves with exercise.

A 30-year-old man presents with a 2-year history of lower back pain, which is worse in the morning and improves with exercise. He also reports occasional stiffness in his hips and shoulders. There is no history of trauma or injury. Over-the-counter painkillers provide minimal relief. He denies any family history of similar symptoms.

Investigations:

HLA-B27 positive

Erythrocyte sedimentation rate (ESR): Elevated

C-reactive protein (CRP): Elevated

X-ray of the pelvis: Sacroiliac joint fusion

MRI of the spine: Inflammation of the sacroiliac joints

Which is the most likely diagnosis?