Hemarthrosis in a Pediatric Patient With Immune Thrombocytopenia and Lyme Arthritis.

The presentation of immune thrombocytopenia is dependent on the degree of thrombocytopenia, with no to mild bleeding symptoms, primarily mucocutaneous bleeding. Severe bleeding in 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 immune thrombocytopenia. 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.