Non-reactive VDRL in secondary syphilis: a clinical case of prozone phenomenon?

Abstract

Introduction: Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. Syphilis is preventable and treatable and can present several manifestations, depending on its stage – primary, secondary, or latent. The prozone phenomenon is a rare situation in which, due to an excess of antibodies in secondary syphilis, the VDRL presents a false-negative qualitative result. This clinical case aims to raise awareness of the existence of this phenomenon and the importance of clinical sense.

Case description: A 44-year-old male patient, with no relevant history, went to an acute illness appointment due to cutaneous lesions spread over the face, chest, back, and upper limbs with one month of evolution, associated with systemic arthralgias, myalgias, weight loss sensation, axillary adenopathy and frontal headaches, bilateral tearing and tinnitus. In the anamnesis, the patient refers to an episode in the emergency department, about five months ago, due to the appearance of a painless penile lesion, which has been medicated with antibiotic therapy with subsequent resolution. It also mentions the practice of unprotected sex. In front of the suspicion of syphilis, in the secondary phase, blood tests were requested, which surprisingly revealed non-reactive VDRL and, in addition, significant liver changes. Given the unpredictable evolution of the diagnostic procedure, the patient was sent to the emergency department, where the diagnosis of secondary syphilis was confirmed by VDRL, TPHA reactivity, and anti-Treponema pallidum antibodies.

Comment: This case demonstrates the importance of prioritizing clinical sense over-diagnose examinations which, due to its contradictory result, could have altered the medical conduct and, ultimately, the latency in the diagnosis and orientation of the patient, with potentially long-term complications, namely the development of tertiary syphilis.