Synovitis secondary to giardiasis in children.

Giardia lamblia, a gastrointestinal protozoan, is one of the most common disease-causing parasites in the world. Giardiasis is primarily encountered in areas with poor sanitation, but it is also seen in more developed countries. A possible sequela of Giardia infections of the bowel is reactive arthritis or synovitis. Few reports of synovitis secondary to giardiasis exist in the literature. Arthropathy secondary to giardiasis is uncommon, but may be underdiagnosed. In this study, Giardia synovitis was diagnosed in two children at a major children's hospital over a 20-year period. Both were boys, aged 7 years, 6 months and 1 year, 8 months at the time of presentation. The knee was the affected joint in both patients, and both cases were initially misdiagnosed as septic arthritis. The synovitis subsided with treatment of the giardiasis, one with cefuroxime and the other with cefuroxime and metronidazole. The diagnosis of Giardia synovitis should be suspected by the presence of Giardia cysts in the stool, similar symptoms in other family members, a synovial white count under 40,000, and an increase in the eosinophil count. Although uncommon, giardiasis can cause severe synovitis that may be confused with a septic joint.