Psoriasiform Sarcoidosis in a Caucasian Male With a History of Psoriasis

Sarcoidosis is a multisystem inflammatory disease characterized histologically by noncaseating granulomas. Cutaneous sarcoidosis has diverse clinical manifestations, including plaques, subcutaneous nodules, maculopapular eruptions, scar lesions, lupus pernio, and, rarely, psoriasiform plaques (Yanardağ et al., 2003). Psoriasiform sarcoidosis is an uncommon presentation. Among patients with sarcoidosis, only 0.9 percent develop psoriasis sarcoidosis, particularly this presentation is more prevalent in patients with darker skin tones (Vega et al., 2016). Although psoriasis and sarcoidosis may occur in the same patient, their coexistence is uncommon (Burgoyne & Wood, 1972). A 66-year-old Caucasian man with a history of psoriasis, psoriatic arthritis, and sarcoidosis presented with a 5.5-cm pink, thickly scaling plaque on the frontal scalp (Figure 1). An initial biopsy demonstrated granulomatous inflammation, which was unexpected given the clinical appearance and history of psoriasis, prompting repeat biopsy for further clinicopathologic correlation. Punch biopsy of the psoriasiform plaque demonstrated psoriasiform dermatitis with dermal noncaseating granulomatous inflammation. The epidermis exhibited hyperkeratosis with neutrophilic parakeratosis, while noncaseating granulomas with accompanying lymphocytic inflammation were present within the dermis (Figure 2). Periodic acid-Schiff (PAS) staining and tissue fungal culture were negative for fungal organisms, and polarization did not reveal foreign material. Laboratory evaluation demonstrated an elevated C-reactive protein of 2.6 mg/dL and elevated angiotensin-converting enzyme level. Chest radiography was unremarkable. Histopathologically, sarcoidosis classically demonstrates noncaseating granulomas, whereas psoriasis is characterized by psoriasiform epidermal hyperplasia, parakeratosis, hypogranulosis, and intraepidermal neutrophils. The simultaneous presence of psoriasiform epidermal changes and dermal noncaseating granulomas in this lesion raised consideration of infection, granulomatous inflammation secondary to a nearby ruptured cyst or follicle, foreign-body reaction, and psoriasiform sarcoidosis. Negative PAS staining and fungal culture argued against fungal infection, while the absence of polarizable foreign material made a foreign-body reaction less likely. In the setting of known psoriasis and sarcoidosis, the combination of a clinically psoriasiform plaque with histopathologic features of psoriasiform dermatitis and dermal noncaseating granulomas, without identifiable infection or foreign material, supported a diagnosis of psoriasiform cutaneous sarcoidosis with overlapping psoriatic features. This case highlights a rare cutaneous presentation of sarcoidosis and demonstrates the importance of clinicopathologic correlation and consideration of sarcoidosis in the evaluation of atypical psoriasiform lesions.