Gout as a differential diagnosis for os trigonum syndrome in adolescent patients
Posterior ankle pain in the adolescent patient population is a relatively uncommon complaint. What is the differential diagnosis for posterior ankle pain in the adolescent population? Most clinicians would not consider gout in the differential diagnosis for posterior heel pain in the adolescent population.
The differential diagnosis specific to adolescent patients may include;
- Os trigonum syndrome
- Achilles tendonitis
- Flexor tendinitis
- Calcaneal stress fracture
- Transchondral talar dome fracture
Gout is caused by the accumulation of purines consumed in our daily diet. Purines are a chemical found in many foods that are typically eliminated through the kidneys as the end product known as uric acid. In some case, and for reasons that are unknown, uric acid is deposited in joints causing acute pain and disability. This painful syndrome is called gout. High levels of uric acid, called hyperuricemia, is a contribuing factor to gout. Hyperuricemia may be caused by a diet concentrated in the foods described below, use of medications that limit the excretion of uric acid in the kidney and dehydration.
Foods that contribute to hyperuricemia include;
- Red meat, particularly heart, liver and kidney
- Dairy products including milk, ice cream and cottage cheese
- Fish and shellfish, particularly herring, anchovies, sardines, mussels and scallops
Drugs that contribute to hyperuricemia include;
- nicotinic acid
- cytotoxic agents.
A 16 y/o active male presented to my office with pain in the posterior right ankle. The patient described daily pain in the posterior ankle that intensified when load was applied to the leg in weight lifting and gym class.
History noted a 16 y/o male with no history of developmental problems. He took no medications, had no allergies to medications and no remarkable past medical history. Physical exam noted palpable pain in the posterior ankle. No edema or erythema was found. No crepitus or pain was found with range of motion of the ankle.
Plain x-rays of the ankle showed separation of the os trigonum with no overt sign of fracture of the posterior process of the talus. MRI (shown above) noted inflammatory changes of the interface of the os trigonum and talus.
In the course of conversation with the patient and his mom, his mom noted an injury to the right little finger two months ago that swelled upon injury and persisted as swollen and painful. No treatment had been sought for the finger injury.
Labs noted CBC normal. Uric acid was elevated at 8.2 mg/dl suggestive of gout.
Treatment was initiated with allopurinal 100mg/day to lower uric acid levels with pending re-evaluation of uric acid planned in 3 weeks.
This is the second case that I have seen in the past two years of adolescent posterior ankle pain that was initially diagnosed as os trigonum syndrome only to be determined to be gout. What is causing hyperuricemia in these cases? Well, like every doc that has a question I turn to the literature for answers. I found a whopping two citations for os trigonum syndrome that was actually secondary to hyperuricemia. (1,2) My hope is that this blog post is the start of a research project that helps to understand why this disease called gout, often viewed as the disease of kings, is now found in children. I don’t have any answers but I’m determined to find a common link in my two patients.
- Rosemol Xaviour , Girijamony V K. Os trigonum – a case report. International Journal of Science and Research, India Edition. Volume 2 Issue 3, March 2013.
- Ersin, E Mehmet, G Serdar A, Intraosseus Tophi Deposit in the O Trigonum. Orthopedics 35(1):e120-3 · January 2012