An Unexpected Outcome in an Adolescent With Juvenile Ankylosing Spondylitis

A 13-year-old boy presented to his pediatrician’s office with a 1-day history of left hip pain. The patient reported that he felt a sharp pain in his anterior left hip while running, causing him to limp. He had difficulty getting out of bed, stating it felt like “needles in the (left) hip when putting my foot down.”

History. He denied other joint pain, swelling, redness, numbness, fever, rash, or recent illness. He denied sexual activity and recent travel. His medical history was significant for a 7-year history of recurrent right hip pain associated with HLA-B27 juvenile ankylosing spondylitis (JAS), attention deficit hyperactivity disorder (ADHD), vitamin D deficiency, low bone density, and traumatic cervical and thoracic vertebral compression fractures at age 11.

During an annual wellness visit 5 days prior to current presentation, he was noted to have left hip pain on internal rotation. Further questioning revealed that pain onset occurred 2 weeks prior to the routine visit, after being tripped. At that time, his pain had mostly resolved and he followed up with his rheumatologist who increased his indomethacin 25 mg to 3 times daily as needed. The patient’s other medications included lisdexamfetamine 30 mg once daily, inconsistent use of over-the-counter vitamin D supplements at 2000 international units (IU) per day, and esomeprazole 20 mg once daily as needed while on prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs). He denied recent corticosteroid use. Family history was significant for arthritis, lupus, type 2 diabetes mellitus, dental decay, and scoliosis.

The patient was well-nourished in moderate discomfort with vital signs within normal limits. He was at the 49^th percentile for height and 58^th percentile for weight with a BMI of 19.58 kg/m². Dentition was within normal limits. He had difficulty bearing weight and required use of a wheelchair.  There was pain to palpation over the anterior femoral head and with internal rotation hip. There was no swelling, redness, increased warmth, bruising, gross deformity, or asymmetry of the lower extremities. His lower extremity sensation and muscle bulk were within normal limits and hips were held in neutral position. There were no skin rashes.

Diagnostic testing. Recent notable laboratory results within normal limits included parathyroid, thyroid, lipids, complete blood count, comprehensive metabolic panel, erythrocyte sedimentation rate, and phosphorus levels. His 25-OH vitamin D was low at 18 ng/mL.