Background: A 14-year-old boy with a 6-year history of recurrent arthritis and enthesitis, which had not responded to previous treatment with NSAIDs, sulfasalazine and methotrexate, presented with a severe flare of these symptoms as well as spinal and sacroiliac joint pain. The patient's father had mild psoriasis.
Investigations: Counts of tender and swollen joints and tender entheses; assessment of spinal mobility; assessments using the Childhood Health Assessment Questionnaire and the Bath Ankylosing Spondylitis Disease Activity and Functional Indices; measurement of erythrocyte sedimentation rate, serum C-reactive protein level and human leukocyte antigen B27 positivity; radiographs of the sacroiliac joints, hips and feet.
Diagnosis: Juvenile-onset ankylosing spondylitis according to the modified New York criteria for ankylosing spondylitis, on the basis of the presence of inflammatory back pain, reduced mobility of the spine and grade 3 bilateral radiographic sacroiliitis.
Management: Treatment with NSAIDs, sulfasalazine and methotrexate did not improve the patient's symptoms. Administration of infliximab 5 mg/kg induced a substantial and rapid improvement in all parameters of disease activity.