Young Peter, 5 years old, strode into my office in the company of his parents sporting a wide, toothy grin. I had looked after him since birth, but after the initial flurry of visits in the first 18 months of life associated with the immunization schedule, I’d only seen him on two further occasions, both times for minor upper respiratory complaints. “What can I do for you today?” I asked Mum and Dad.

“Peter has a very unusual way of running,” Mum replied. “He tends to throw his right leg out to the side when he picks up speed.”

I must admit that diagnosing gait disturbances in children has always been a bit of a confusing topic for me. The parents had noted the problem for the last few months, the boy did not seem bothered by it in the least, and there were no other complaints. He’d hit all of his developmental milestones without delay, but had recently begun having difficulty keeping up with other five-year-olds at the playground. This was not due to any significant shortness of breath. “Well, let’s get him out into the hallway and see,” I said.

Peter did in fact have an unusual way of running. He ran with his head hunched forward and in order to get his right leg in front of him, he had to swing his right hip laterally in an exaggerated circumduction. On examination, his hips had a full range of motion but there seemed to be weakness of both glutei, the right more so than the left. The only other physical finding of note was that of an unusual, barrel-shaped chest that I hadn’t appreciated before. His weight was in the 75^th percentile and his height was in the 25^th.

Widespread abnormalities

I referred Peter to a pediatric physiotherapist with a specialty in gait disturbances. The physiotherapist found the following abnormalities:

• no lumbar lordosis but a kyphotic thoracic and lumbar spine
• an asymmetrical, enlarged rib cage
• weakness of the hip abductors, adductors and extensors
• trigger fingers in both his right and left hands.

Before proceeding with any exercises, she wondered if there was an underlying diagnosis that might account for all of the abnormalities.

I made a referral for Peter to be seen by a paediatrician. While waiting for this appointment though, I ordered x-rays of the patient’s chest, pelvis, hips and spine. The report, when I received it a couple of days later, came as a shock.

Peter’s skeleton appeared “coarsely trabeculated.” There was anterolisthesis of L1 and L2, “abnormal acetabular screws with tombstone-appearing iliac bone,” and widely-spaced ribs. The radiologist suggested a diagnosis that proved to be correct. Can you guess what it was?