GD14: An unusual case of secondary syphilis masquerading as pemphigus vulgaris

Paula Beatty, Geraldine Quinn and Muireann Roche

Beaumont Hospital, Dublin, Ireland

Syphilis is a sexually transmitted disease caused by the spirochaete Treponema pallidum. Once a rare disease, its incidence is increasing, with the World Health Organization reporting approximately 6 million new cases occurring annually in people aged 15–64 years. Known as the great masquerader, it can mimic numerous other conditions, often resulting in delayed diagnosis. We report the case of a white female with secondary syphilis presenting with an erosive eruption reminiscent of pemphigus vulgaris. Rarely reported in the literature, our case highlights the potential systemic sequelae of this diagnosis. A 37-year-old woman presented to the dermatology clinic with a 6-week history of a mildly pruritic, generalized erosive eruption. On examination, she had diffuse erosions affecting the face, neck, upper limbs, abdomen, lower limbs and vulva. Our working diagnosis was pemphigus vulgaris, given the patient’s age and the absence of intact bullae. Investigations, including skin autoantibodies, antinuclear antibody, HIV, hepatitis B, hepatitis C and Venereal Disease Research Laboratory test, were performed, in addition to a skin biopsy. Treatment was commenced with oral prednisolone and aciclovir to cover for a likely superimposed herpes simplex infection, due to the well-circumscribed appearance of the erosions. One week later our patient presented to the emergency department with unilateral weakness and slurred speech. An urgent computed tomography (CT) of the brain demonstrated an acute middle cerebral artery infarction, and thrombectomy was performed. Her cutaneous findings had also progressed with new erosions having developed in the intervening days. She was commenced on intravenous (IV) steroids, doxycycline and nicotinamide. Skin biopsies returned an intraepidermal vesicle with extravasated red blood cells, abundant polymorphs and plasma cells. Direct immunofluorescence (DIF) was negative. Our working differential diagnosis at this point included Sneddon Wilkinson subcorneal pustular dermatosis, IgA dermatosis or a paraneoplastic phenomenon. However, negative DIF and skin autoantibodies and a normal CT of the thorax, abdomen and pelvis led us to pursue further investigations. Remaining outstanding investigations eventually led us to the unifying diagnosis. Syphilis serology returned a positive result with a ratio of 1 : 20 480 and positive T. pallidum IgM, suggestive of secondary syphilis. Treatment was commenced with IV benzylpenicillin and her cutaneous symptoms resolved over the subsequent days. Syphilis continues to represent a diagnostic challenge for clinicians owing primarily to the diversity in clinical presentation. Secondary syphilis presenting with pemphigus-like erosions is a rare phenomenon in immunocompetent adults. As our case illustrates, syphilis is also associated with a multitude of complications that may further impede or delay diagnosis and recovery for our patients. It is imperative that clinicians continue to have a high index of suspicion for the diagnosis of syphilis in unusual dermatological presentations that are slow to respond to standard treatment.