False Positive Babesia microti Result in New-Onset Systemic Lupus Erythematosus Manifesting With Febrile Illness.

False positive serologic results are common in systemic lupus erythematosus (SLE) due to the presence of autoantibodies. We present a case of a young patient initially suspected of having a tick-borne disease with a false positive Babesia microti antibody result, and later diagnosed with SLE. Acute babesiosis was excluded after additional laboratory tests such as Babesia polymerase chain reaction (PCR) and blood smear for parasites. The patient's symptoms were then thought to be a new manifestation of SLE and prompted the initiation of systemic steroids with subsequent improvement. False positive serologic Babesia microti test result was attributed to SLE autoantibodies.