Unilateral knee swelling in a child due to Lyme disease


In their case report, “Pediatric unilateral knee swelling: a case report of a complicated differential diagnosis and often overlooked cause,” Guardado et al. describe a 3-year-old girl who presented to a hospital in Pennsylvania after two weeks of limping from a swollen right knee.¹

According to the authors, “The mother initially denied history of a tick bite, yet after focused questioning, the mother stated that the child had ticks on her approximately 9 months ago.

Unfortunately, the child was not taken to her clinician because she did not develop any skin rashes which could indicate Lyme disease.

The child demonstrated right knee effusion with signs of crepitus and decreased range of motion secondary to swelling, the authors explain. “In addition, she had an unsteady gait without joint tenderness, crepitus, or overlying skin pathology.”

A Western blot test for Lyme disease was positive.

“Lyme arthritis is a diagnosis that is often missed, even in children, who are the population with the highest incidence of Lyme disease,” the authors point out.

“When this diagnosis is missed, it can result in long-term morbidity, which is generally refractory to intravenous antibiotic therapy, oftentimes requiring synovectomy.”

The child had a complete resolution of symptoms following a 2-day treatment with IV Rocephin and 21 days of oral amoxicillin.

“This case demonstrates the importance of including Lyme arthritis as part of the differential diagnosis of joint swelling regardless of the recollection of a tick bite,” the authors suggest.

Furthermore, the case raises awareness of mono- or oligoarticular arthritis as one of the signs of Lyme disease.

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