Atypical behaviour of specific antitreponemal IgM in active and treated syphilis

Negative 19S (IgM) test in patients with active untreated syphilis and reactive 19S (IgM) test in a group of patients with treated syphilis are reported. The practical value of IgM test in routine serodiagnosis and monitoring of the treatment of syphilitic infection as well as the theoretical aspects of the IgM reactivity are discussed.