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Knee Problems in Children Can Be Difficult to Diagnose
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Posted on: 09/15/2011
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Sometimes one disease mimics another one so closely, it is difficult to tell them apart. That's the case with two separate knee problems that look very similar. One is a problem called venous malformation. The other is juvenile idiopathic arthritis (JIA).
This article was written by physicians from Children's Hospital of Boston. The information is intended to help other physicians become more familiar with the problem of misdiagnosis of knee venous malformation. Mistaking it as juvenile idiopathic arthritis can delay proper treatment.
Juvenile idiopathic arthritis is a chronic condition of joint swelling and inflammation. The term 'idiopathic' tells us there's no known cause. Venous malformation is as the name describes.
Venous refers to the veins (blood vessels that return blood to the heart). The malformation is a jumble of veins often forming a clump or circle of veins. The effect of the malformation is to slow the blood down and keep it from moving through the area as it should.
Both conditions present with joint pain and swelling. When venous malformation causes these symptoms in a child, the natural diagnostic suspicion is for the more common juvenile idiopathic condition. Knee venous malformation is so rare, it is not easily recognized.
So how often does this problem get misdiagnosed? And how can the physician sort this out? The authors reviewed their records for an 11 year period of time and found 56 children who had venous malformations of the knee. Six of those children were treated as if they had juvenile idiopathic arthritis before the accurate diagnosis was made.
By taking a look back, it's possible to identify some characteristics of knee venous malformation that might be the tip off that it's not arthritis. Of course, as the old saying goes: "Hindsight is 20-20." In other words, it's much easier to look back at what was really going on but difficult to understand at the time it was happening.
Even when the malformation creates a mass that is removed, the jumble of blood vessels can look so much like a hemangioma (benign blood tumor) the diagnosis remains clouded. Sometimes it's not until the mass grows back or the family seeks a second opinion that the real diagnosis is made.
MRIs and ultrasound studes are very helpful. These tests show blood filling in spaces within the muscles. This is a characteristic sign of venous malformation. Combining the results of imaging studies with biopsy of the tissue mass helps make the differentiation of venous malformation from juvenile idiopathic arthritis.
Sometimes the diagnosis isn't made until the child is treated for arthritis without success. The more difficult cases are when the symptoms improve with antiinflammatories used for arthritis so it looks like the right diagnosis was made. It isn't until the child is taken off the medication and the symptoms come back that a second (or third) look help reveal the true problem.
Other differentiating factors are very subtle. For example, juvenile idiopathic arthritis often affects all the large joints (knees, ankles, wrists, and elbows). Venous malformation presents at the knee most of the time. Lab tests may show some differences that can be helpful but this is not 100 per cent accurate.
Most of the time it's the imaging studies that help define the problem. And because knee venous malformation is congenital (present at birth), the earlier MRIs are used the sooner the problem is identified correctly. Early recognition doesn't always happen because symptoms don't develop right away at birth. Some children don't develop visible problems until years later.
There's one other important clinical finding that can help tell these two conditions apart. Although both conditions cause joint pain and swelling, with knee venous malformations, there are often some skin changes that can be seen. The veins become more prominent on that side. There may be swelling above the kneecap. And the skin around the knee looks blue in color.
The authors provide a summary of the six case reports of patients with knee venous malformation who were misdiagnosed with arthritis. Each one had a unique presentation that made the diagnosis particularly difficult. Reading each case along with the authors' analysis may help other physicians when faced with complex or unusual knee problems in children.
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References:
Andy Tsai, MD, PhD, et al. Misdiagnosis of Knee Venous Malformation as Juvenile Idiopathic Arthritis. In Journal of Pediatric Orthopaedics. September 2011. Vol. 31. No. 6. Pp. 683-690.
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*Disclaimer:*The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic. |
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