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It’s a busy winter evening and the Pediatric ED is hopping. Lots of acute illness and  fever. At the moment, there’s a new kid in room 1 with the chief complaint of “not walking.” OK, this one could be interesting. You go down the hall to see what gives.

The child is 20 months old. The parents say that their doctor told them to make an appointment to see a neurologist for a work-up but they were worried and the appointment line said it would be a few weeks before he could be seen. The child has been intermittently refusing to walk for 6 weeks and they want some answers.

About six weeks ago he seemed to be in his usual state of good health. He was playing and was struck in the right shin by a toy wagon. He cried and stopped bearing weight on the right leg. Since that time he’s seen his pediatrician several times and an orthopedist as well. Sometimes he’ll begin to bear weight again but then he stops. Over the time period he had a cold, lost some weight, ran a fever, but nothing that has persisted. Four days ago he began to refuse to crawl. Back to the orthopedist, where labs were sent including a CBC, ESR, CRP, ANA and Rheumatoid factor. The CRP came back mildly elevated at 2.2. The ANA and Rheumatoid factor were negative. However, the CBC and ESR clotted and the patient was sent home before the test results were known or could be repeated. The orthopedic note ended with a plan to do a bone scan in the near future. The pediatrician felt that the on-again, off-again weight bearing might be a neurologic problem and said he would refer for a work-up.

On examination, you don’t find much. The vital signs are unremarkable. The child is sitting up on the gurney, looking at a picture book. He begins to cry and fuss when you try to examine him. He has no redness, swelling or deformity anywhere along the right leg, no obvious point tenderness, and you are able to put all joints through passive range of motion without any more fussing then he was already exhibiting when you first approached him. His neuro exam seems nonfocal, as best you can tell given his age and limited cooperation. He certainly doesn’t appear to have any weakness in the right leg but when his mother stands him he draws it up and refuses to put weight on it.

So, struck in the leg 6 weeks ago with a history of refusal to walk on and off again ever since. Two sets of negative plain films. What could this be?

Trauma: The mother clearly feels that the wagon bumping into him corresponded with the onset of his symptoms. Frequent traumatic injuries in children under 4 yrs of age include toddler’s fracture, stress fracture, or child abuse. Sometimes fractures are subtle and don’t show up on initial plain films. But over the course of six weeks you’d think he would have had time to develop subperiosteal new bone formation. That isn’t generally hard to spot on plain films.

Infection: Common causes of infectious limp in a toddler include septic arthritis, transient synovitis and osteomyelitis. The exam doesn’t really point to a particular joint and the course is a bit long for septic arthritis. You’d think an experienced Orthopedist who’s been following this kid would of picked it up by now. Transient synovitis of the hip is also usually of fairly brief duration. But osteomyelitis is a thought. At this point a bone scan might be a nice way to look for this. Of course, it’s after hours and Radiology isn’t going to do it tonight.

Rounding out the list of frequently etiologies of limping in very young children are the congenital causes (think developmental dysplasia of the hip) and neuromuscular problems, such as cerebral palsy. Neither should suddenly appear in a previously normal toddler, should they?

OK, time to consider less common causes. People limp for three reasons: pain, weakness, and deformity. The child has good muscle tone and strength; maybe weakness is less likely. If the child had a congenital deformity, it should have shown up before this. You decide to focus your differential on pain.

Six weeks of painful limp? Think fracture, inflammation, infection. At this point you definitely want to pursue blood work. And what else could cause bone pain? Maybe this is a bit more sinister. You also heard the mother mention fever and weight loss over this time period. She attributed it to a URI and sinus infection. But maybe there is a malignancy. Too bad that CBC clotted a few days ago. Time to repeat it.

You grab an order sheet. Although plain films have been done already, they remain the highest-yielding screening test in a child with limp. You order X-rays from the hip on down. The bone scan you want you can’t have, so save that thought for now. A CBC, ESR, and CRP are also excellent screens for inflammation, infection, and hematologic malignancy.

********
 
A while later the labs are back and you’re glad you got them. The child is pancytopenic with a CRP of 3.4 and ESR of 140. You call the oncologist who comes in and admits the child and you aren’t very surprised later to learn that the child has pre-B cell leukemia.

There’s a rule in medicine: If you don’t think of it, you can’t diagnose it. Don’t forget to add acute leukemia to your differential diagnosis of limping in a child. A reasonable work-up for a limp you just cannot figure out or localize is a set of plain films, CBC, ESR, and CRP. This won’t always find the cause but is a great way to get started and will pick up most of what you’re looking for.

Amy Levine, MD, is an associate professor of pediatric emergency medicine at UNC Chapel Hill
 

Comments   

# limping todlermariam 2011-08-23 13:41
thanks for this article
my baby start limping after fever she is only one year and half -am waiting for her labs and am v worry
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# Agree with your rule: If you don't think of it, you can't diagnose it"Nguyen H. Nguyen, MD 2012-02-23 07:15
Very helpful article, to keep us Pediatricians in the front line on our toes. May I repeat your point that what this child had is an uncommon cause of limping in a child, so that parents don't get unnecessarily alarmed when there is a much more likely reason for their child to limp at this age (one of them is transient synovitis of the hip), but that lasts only a few days, not months.
Thanks for the article.
Reply
# On and off limping toddler Lou 2012-03-21 08:04
My little girl is now 23 months, three and a half months ago she had her mmr shots and six days later had an awful limp not even able to stand. This went on for a couple days and went away, a week and a half later came back. This went on for about ten weeks. She has had three blood tests with raised crp and she has never been a great sleeper.
In and out of Dr's, one Dr said he had seen it before, doesn't know what it is, but it will go away....so I turned to google spending countless hours searching and her symptoms always matched JRA. The pediatrician treating her never sent her for testing so did not find out if that may be it...and then I came across a I site that said dairy allergy can cause raised crp and arthritis...I took her off dairy and she now sleeps better, crys less, and the limp has not come back. The pediatrician said dairy has nothing to do with it and was annoyed I took my daughter off of it.
Her crp was still slightly elevated after two weeks of being mostly dairy free, grandparents seem to have a hard time listening to what I feel is right for my child.
I am still waiting to see an allergist and for results of stool sample...loosin g faith in system wondering who else I can go to for answers.
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# 6mth old went limp both legs 1day after 6mth immunisations for 12 daysAinslie 2012-11-08 01:54
Lou, we have had simaler situation to you have you gotten any answers? 3 weeks on and we are still searching for answers?
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# 19 month year old, going through the same thing.Heather 2014-07-24 13:06
I have a happy healthy 19 month year old, who is displaying the same symptoms. She had surgery for hip dysplasia a year ago and appart from the angle on her being being higher at 28 degree instead of the 20 we hoped for she has been running around and developing like a 'normal' child.

3 weeks ago, we noticed that she was having trouble walking , which turned into an intermittent limp. We have been back and forth to the hospital as she has been diagnosed with Snapping tendon?! Perthe's disease and irritable hip, all in the space of a week. The doctors are not interested and not helping the situation. Finally i demanded blood work, where her ESR can back as 84, however her CPR was normal, but she is still intermittedly limping, with nobody trying to find the cause or help with a diagnosis! She has had x-ray to see if her hip was dislocated - it wasn't but we keep getting ignored as medically, except for the pain / discomfort and ESR there is nothing wrong with her to look at.
Whilst in hospital her ESR lowered but her white blood count raised before we were discharged - but we still have found no reason. If you are a private consultant, please help me with this matter. As on my own and with the help of the internet, i have come to two conclusions of what it could be: juvenile arthritus or leukemia!
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