Pediatric Medical Mystery I

A 6 year old girl presents with one day of progressing left hip and back pain. She woke up in the morning complaining of minor pain of her hip and left leg. Mom gave tylenol and sent her to school. At school, the pain got worse and she began favoring her right side. She described the pain as extending from back to hip to ankle, difficult to characterize, difficult to identify radiation. Otherwise, she was healthy. She had an upper respiratory tract infection a week ago with a resolving cough. A complete review of systems (including travel, tick bites, animal encounters, and trauma) was negative.

By evening, she was inconsolable, crying and screaming because of the pain. Her parents brought her into the emergency department in South Bay. She was afebrile, bearing weight, non-toxic, but clearly uncomfortable. Labs were significant for normal ESR (14), CRP (4.5), CBC (WBC 11 with 63% neutrophils), chemistries, LFTs, U/A. A CT of the hip showed "no osseous abnormality, no fracture or dislocation, no soft tissue abnormalities or mass." Despite these reassuring labs, the emergency department decided to send her here.

That turned out to be the right decision.

They were worried about a septic arthritis of the hip, one of the few pediatric orthopedic emergencies. When I evaluated her, she did not look sick and she was still afebrile. Her range of motion of the hip seemed to be limited by pain. She had external and internal rotation, limited flexion, limited extension. Her knees were fine. On examination of her back, she had exquisite paraspinal tenderness 1-2cm left of the lumbar spine. She did not want to stand. Her exam was otherwise unremarkable.

Our differential diagnosis was broad, encompassing toxic or transient synovitis, osteomyelitis, joint or peri-vertebral abscess, diskitis, lyme disease, Legg-Calves-Perthes, musculoskeletal injury or strain, slipped capital femoral epiphysis, stress fractures, rheumatologic diseases, abdominal etiologies, kidney stone, pyelonephritis. We decided to be conservative. We gave ibuprofen and consulted orthopedic surgery to rule out a septic hip. They didn't think it was a septic hip but suggested a bone scan or MRI of the spine to rule out diskitis or other infection. A bone scan would be easiest but would not show soft tissue well (which we were worried about because of the paraspinal tenderness). An MRI is expensive and requires sedation for a 6 year old. We managed to schedule an MRI for the following morning.

The next morning, I went to examine her at 0740. She was walking to the bathroom with her mother. Although she favored her right side, she was able to bear weight. She looked good; she was afebrile, talking, interacting appropriately. Her pain was better, and we decided it must have been a transient synovitis (a benign inflammatory condition following a URI).

At 0830, in the middle of Grand Rounds, we were paged to bedside. She was lying still on her back, looking very uncomfortable. She had a 10/10 headache, photophobia, and nausea; she had vomited three times and was unwilling to move her neck, back, or lower limbs. Her mental status was fine. We were immediately concerned for meningitis. But do we do a lumbar puncture? We were afraid that she had an infection of the soft tissues of her lumbar back, and sticking a needle through that would not be safe.

We sent off labs and cultures and consulted infectious disease. Over the day, her exam changed, and she was able to move her neck more (though extension was still limited). The nausea and vomiting stopped after ondansetron (Zofran). However, she did start having fevers and neck pain. When ID came to see her, they did not think she had bacterial meningitis, but they were worried about some sort of infection.

Her labs came back late in the afternoon. Her ESR had gone up to 56 and her CRP was sky high, 208, even though they were normal two days prior. Her white count was 25.8 with 95% neutrophils. A U/A was negative. We wanted a stat MRI; the residents stayed late trying to get everything organized. With a bit of sedation, we got a look at the lumbar spine.

I love this stuff. The exciting conclusion of this case will come tomorrow.