Rupioid psoriasis: A complex, multifactorial presentation

Abstract

Introduction: Secondary syphilis, also termed the great mimicker due to its vast array of clinical presentations, is associated with skin manifestations including rupioid, macular, psoriasiform, and condylomatous lesions. On clinical examination alone, it can be difficult to differentiate between rupioid syphilis and rupioid psoriasis, especially among cases of human immunodeficiency virus (HIV) and syphilis co-infection; however, histologic examination can aid in their differentiation. Additional testing such as serum rapid plasma reagin (RPR), anti-HIV antibody, rheumatoid factor, and fungal cultures should be performed to exclude other causes of rupioid lesions. Case Report: A 19-year-old HIV-positive male developed numerous hyperkeratotic skin lesions involving the head, trunk, and extremities over a 4-week period. His RPR was positive (1:64), suggesting a diagnosis of rupioid syphilis. The patient was treated with doxycycline, given a reported history of penicillin allergy. Rapid plasma reagin titers decreased to 1:2 following treatment; however, the skin eruption did not improve. A biopsy of a lesion demonstrated psoriasiform acanthosis with confluent hyperkeratosis, clusters of intracorneal neutrophils, and negative spirochete immunostaining. Based on histopathology and clinical presentation, a diagnosis of rupioid psoriasis was favored. The patient was started on targeted anti-psoriatic therapy with apremilast and maintains close follow-up with his dermatologist every three months. Conclusion: Although the patient’s presentation was initially presumed to be secondary to syphilis, his lack of response to treatment prompted further workup to assess the etiology of the patient’s skin findings more accurately. In doing so, a diagnosis of rupioid psoriasis was favored based on the histologic findings observed.