Introduction:

False-positive treponemal tests can be obtained in patients with Lyme disease, but the coincidence of two spirochetal infections – early syphilis and Lyme disease – should also be considered.

Objective:

Our case illustrates that even though Lyme disease and early syphilis are frequent, their coincidence is extremely rare.

Case report:

A 27-year-old man presented with generalized erythematous rash typical of secondary syphilis, concomitant with erythema migrans. The diagnosis of early syphilis was confirmed on the basis of positive serological tests. Treatment with doxycycline 200 mg daily for 14 days was applied.

Conclusions:

Treponema pallidum and Borrelia burgdorferi, both members of the Spirochaetaceae family, are causative agents in the etiopathogenesis of syphilis and Lyme disease, respectively, with increasing rates of both infections seen in recent years. Nevertheless, the possibility of false-positive treponemal tests during Lyme infection should also be considered to avoid misdiagnosis and inappropriate treatment.