The Great Imitator: Latent Neurosyphilis Revealed After Initiation of the Immunosuppressive Drug Secukinumab

Syphilis is a multi-organ system bacterial infection caused by the bacterium Treponema pallidum. Syphilis can advance through four clinical stages: primary, secondary, latent, and tertiary. Once in the tertiary stage, mortality is seen in up to 58% of individuals. Here, we present a case of latent neurosyphilis manifesting after initiation of the immunosuppressive medication secukinumab, a monoclonal antibody that antagonizes interleukin-17A. A 66-year-old male with type II diabetes mellitus, hyperlipidemia, and rheumatoid arthritis presented to the emergency department for a right lower quadrant abdominal cellulitis at the site of his insulin pump. On examination, a non-blanching papular rash on the palms and soles with several scaling papules was discovered. No visible pustules, oral lesions, or perirectal lesions were seen. Neurological examination was noncontributory. His past medical history revealed initiation of secukinumab for the management of rheumatoid arthritis two months prior to presentation. The rash developed six weeks after starting secukinumab. Basic laboratory tests, including a complete blood count, thyroid panel, renal function panel, fasting blood glucose, electrolytes, and C-reactive protein, were within normal limits. A hepatic panel revealed mildly elevated alkaline phosphatase, alanine transaminase, and erythrocyte sedimentation rate Westergren level. Laboratory tests for hepatitis B, hepatitis C, HIV-1, Chlamydia trachomatis, and Neisseria gonorrhoeae all returned negative. A rapid plasma reagin (RPR) titer returned positive at 1:128, and a serum Treponema pallidum Ab returned reactive. Lumbar puncture serologies demonstrated a positive Venereal Disease Research Laboratory (VDRL) test. The patient was diagnosed with latent neurosyphilis and started on intravenous crystalline penicillin G for three weeks. A thorough history, comprehensive physical examination, and basic workup should be performed in any individual prior to immunosuppressive medication initiation. On initial presentation, our patient had an isolated rash on the palms and soles, which is classical for secondary syphilis. The specific manifestations seen in syphilis depend upon the timing, site, and immune status of the individual. Due to its ability to have a variety of presentations, syphilis should always remain on the differential for any physician caring for immunocompromised individuals. Again, initiation of immunosuppressive medications, such as the monoclonal antibody secukinumab, can result in the reactivation of previously dormant infections. As physicians, we must carefully screen our patients prior to initiating immunosuppressive agents to prevent disease reactivation.