False-positive TPPA and TRUST syphilis test results in a patient with antiphospholipid syndrome and monoclonal immunoglobulinaemia

A 56-year-old woman presented to our hospital service with headache and neck and shoulder pain. She was eventually diagnosed with antiphospholipid syndrome and monoclonal immunoglobulinaemia of unknown significance (MGUS). The Treponema pallidum (TP) particle agglutination assay (TPPA) and syphilis toluidine red unheated serum test (TRUST) were positive with TPPA 1:20 480 and TRUST 1:131 072. HIV and hepatitis tests were negative. Previous medical history included four miscarriages for unknown causes. No skin rash or other abnormalities suggestive of syphilis were observed. Her spouse was healthy and showed negative syphilis serology. There were no other partners. Based on a diagnosis of latent syphilis, she was given the recommended penicillin therapy. However, after three courses of treatment, the TRUST titre was 1:32 768, and the TPPA titre remained unchanged with 1:20 480. TP IgM was positive by immunoblotting, whereas ELISA IgG anti-TP assays (TP-ELISA) and the fluorescent treponemal antibody absorbed test (FTA-ABS)...
Source: Sexually Transmitted Infections - Category: Sexual Medicine Authors: Tags: Open access PostScript Source Type: research