The Case: A 22 mo boy with acute on chronic knee pain, with normal exam and work up in the ED notable for mildly elevated inflammatory markers and normal imaging.

Here’s how you answered the questions:

Discussion:

The major dilemma in this case how much of a work up for a chronic compliant with recent worsening. More complicating is the fact that this patient is afebrile in the ED with a normal exam (despite reported acute worsening). However, the majority would obtain some lab work (CBC, ESR, CRP), given unclear history and broad differential.

For imaging, many agreed that X-rays are likely low yield, but Drs. Isbey and Zaveri mentioned that this may serve as observation time. While hip US is likely the highest yield for a swollen joint/effusion, many would not obtain in this case given lack of swelling on exam. Dr. Simpson mentioned the use of X-ray in the event that the patient returns so you have a baseline. She also suggested using Cerner Capture to augment documentation of a normal knee exam.

With an unclear history and work up that doesn’t clarify your differential, many would also phone a friend and discuss with a consultant. With normal X-rays, orthopedics would unlikely have more to add. Rheumatology may help with guiding additional work up, as well as provide and follow up for a patient who likely doesn’t meet admission criteria.

As for the differential diagnosis, infectious, rheumatolotic, or oncologic were highest on participants’ lists. Dr. Guse added that Lyme monoarthritis where the knee joint is most commonly involved and a course that fits with Lyme as well. The swelling can also come and go as it reportedly has for this patient. Dr. Shaukat raised the point that if this were Lyme, it would represent late disseminated disease, which, if this child were presenting in the spring, would mean that he was exposed in the winter which is unlikely.

Denouement:

Rheumatology was consulted given the mildly elevated inflammatory markers. Low concern for JIA given history however offered to follow patient has an outpatient concerned with the microcytic anemia, although most likely iron deficiency could point to an oncologic process. Heme/Onc was then consulted who agreed and requested additional labs including an LDH, Uric Acid, BMP and iron studies.  All were unremarkable. Patient was discharge home to be followed up with Rheumatology.

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