Lyme pseudothrombophlebitis in a young child

This case report, featuring an 8-year-old boy, illustrates, once again, the unusual presentation that can occur with Lyme disease. [1] The child was admitted to the emergency department at Jefferson University Hospital in Philadelphia with swelling and pain in his knee and calf.

The pain had been ongoing for one week. “He described the pain as throbbing, worse with movement, and improved with rest,” writes Sandelich and colleagues.  Three days earlier, the boy had visited a different emergency department and was diagnosed with a muscle sprain following results from an X-ray.

The boy’s pain, however, continued, and an ultrasound of the lower extremity was obtained. It revealed “a 13 x 6 x 2.7-cm heterogeneous mass with solid and cystic components in the left calf,” writes Sandelich.

An MRI revealed several findings that were consistent with a large collection in the left gastrocnemius muscle with surrounding myositis involving the gastrocnemius muscle.

A Lyme Western blot test was positive, and the child was diagnosed with Lyme pseudothrombophlebitis. He was treated successfully with intravenous cefazolin, followed by 4 weeks of amoxicillin.

“A known complication of a ruptured popliteal cyst is a pseudothrombophlebitis,” explains Sandelich. A popliteal cyst, also known as a Baker’s cyst, has been reported in Lyme disease.

The authors caution, “The clinical presentation in this case is similar to that of a DVT [deep venous thrombosis), and obtaining an ultrasound of the deep leg veins is imperative.”