Serologies in Lyme disease can be deceiving: a rare case of mycoplasma-induced figurate erythema with persistent IgM Lyme antibodies

We present the case of a 65-year-old woman who came to our clinic with a pruriginous annular skin eruption suggestive of erythema migrans. She reported a previous mild respiratory syndrome. Given the suspicion, the patient was empirically given doxycycline 100 mg q12h for two weeks, which led to a resolution of the dermatosis. Initially, laboratory tests revealed positive IgM for Lyme disease, however these IgM persisted for several months of longitudinal follow-up and IgG was never positive. Seroconversion occurred, however, for Mycoplasma pneumoniae over the course of three weeks. M. pneumoniae is known to cause mucositis, but to our knowledge this is the first reported case of Mycoplasma-induced figurate erythema. She maintained longitudinal follow-up at our clinic and showed no signs of recurrence during this period.