Background: A 49-year-old man presented to a rheumatology clinic with a 2-month history of low back pain. The pain seemed to be inflammatory in origin, with nocturnal occurrence and substantial early morning stiffness. The patient was previously well, with no history of psoriasis, inflammatory bowel disease or iritis.
Investigations: Physical examination, anteroposterior X-ray of the pelvis, isotope bone scan, CT and MRI of the sacroiliac joints, measurement of serum inflammatory markers, HLA-B27 testing, routine and mycobacterial culture of the sacroiliac joint fluid aspirate, tuberculosis skin testing and chest X-ray.
Diagnosis: An HLA-B27-negative patient with chronic unilateral sacroiliitis refractory to conventional management.
Management: After unsuccessful treatment with various NSAIDs and physical therapy, local corticosteroid injections on two occasions in the affected sacroiliac joint provided transient relief. A subsequent 20 mg injection of infliximab into the affected joint resulted in clinical and radiological improvement that has been sustained for more than 2 years.