Erythromycin failure in the treatment of syphilis in a pregnant woman.

A pregnant woman with a history of allergy to penicillin was diagnosed as having primary syphilis. Two successive courses of erythromycin therapy failed to cure the infection. Penicillin desensitization and therapy were initiated and were successful. The newborn was diagnosed as having probable congenital syphilis. This case emphasizes the need for close follow-up of pregnant women after erythromycin treatment for early syphilis.