Diagnostic use of MRI in the non-mobile infant.

DESCRIPTION A previously mobile 13-month-old toddler presented to the paediatric emergency department following a fall with subsequent reluctance to weight-bear. A fractured femur was strongly suspected initially, but was not confirmed on x-ray. She was followed up in fracture clinic for 10 days. She deteriorated further evidencing a reluctance to sit and screaming episodes when lying supine but not when lying prone. Inflammatory markers were raised with white cell count of 15.79×10/l, neutrophils 5.89×10/l, c reactive protein of 39 mg/l and erythrocyte sedimentation rate of 60 mm/h. An MRI performed 14 days later revealed lumbar discitis with associated vertebral osteomyelitis (figures 1–3). She received intravenous antibiotics for 4 weeks followed by oral antibiotics for 6 weeks and made a good recovery. Discitis is rare in children. Presenting symptoms include a limp or refusal to walk, and older children can present with back pain. A high index of clinical suspicion is required and therefore diagnosis is often delayed. The mean duration of symptoms can be 24 days prior to presentation and average diagnosis can be delayed by a further 12 days postpresentation.