Actinic Granuloma Complicated by Secondary Syphilis: A Case Report

Actinic granuloma (AG) is a rare skin eruption thought to result from a sun-induced inflammatory response attracting giant cells, which are large, multinucleated, and inflammatory, to form granulomas and degrade surrounding elastic material. Clinically, lesions begin on sun-exposed skin as pink papules and nodules that coalesce into demarcated annular plaques with a hypopigmented center. Histologically, actinic elastosis surrounds the outer annulus ring, with histiocytes and giant cells within the raised border, and the innermost central zone is filled with minimal to absent elastic fibers.

We present a middle-aged female with a pruritic eruption of diffuse erythematous macules and papules coalescing into plaques with mild scale involving the scalp, face, neck, torso, and upper and lower extremities, including the palms and soles, but sparing the ears, bilateral axillae, elbows, and knees. Skin biopsies revealed solar elastosis and abundant multinucleated foreign body giant cells with ingested elastic fibers. The patient's clinical presentation and histopathology were consistent with a diagnosis of AG. Furthermore, spirochete immunostaining of the specimens revealed multiple Treponema pallidum spirochetes throughout the epidermis and dermis. Secondary syphilis with primary chancre was added to the diagnosis. Treatment included oral and topical steroids followed by intravenous penicillin G. After 1 month, all lesions had resolved with post-inflammatory erythema.

Our patient differs from the typical presentation in describing intense pruritus with her eruption. This interesting collision reminds clinicians to retain a high index of suspicion for multiple diagnoses in a single patient.