Hemarthrosis in a pediatric patient with idiopathic thrombocytopenic purpura and Lyme arthritis

Presentation of idiopathic thrombocytopenic purpura (ITP) is dependent on degree of thrombocytopenia with no to mild bleeding symptoms, primarily mucocutaneous bleeding. Severe bleeding of other organ systems is a rare complication. Spontaneous hemarthrosis is rare in patients without hemophilia. We report a child presenting with oral and cutaneous petechial lesions and left knee hemarthrosis without trauma. Laboratory findings showed severe thrombocytopenia consistent with ITP. Serologic tests were consistent with Lyme disease. Hemarthrosis was presumed secondary to Lyme disease monoarticular joint inflammation with bleeding exacerbated by severe thrombocytopenia. Hemarthrosis resolved and platelet counts normalized following immunoglobulin infusion, steroid course, and antibiotics.