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Case Reports

Abstract

A 72-year-old man with a history of squamous cell carcinoma of the lung in remission after undergoing adjuvant chemotherapy with carboplatin and paclitaxel followed by immunotherapy with pembrolizumab presented with thickening of the palms and soles for 5 months. The patient noted the cutaneous changes developed while receiving immunotherapy and were characterized by thickening and peeling of his palms and soles with associated pain and pruritus, as well as thickening of his fingernails and toenails. Physical exam was notable for hyperkeratotic plaques of the palms and soles, along with thickened yellow nails with onycholysis and subungual debris of all toenails and fingernails. A toenail clipping obtained was negative for fungal organisms. Treatment with oral terbinafine was deferred due to concern for hepatotoxicity. He was advised to start 12% lactic acid lotion for his palms and soles without improvement. A punch biopsy of the palm was performed for further workup. Histologic sections revealed a stratum corneum with intracorneal serum and parakeratosis alternating with compact hyperorthokeratosis. The underlying epidermis demonstrated papillomatosis, acanthosis, hypergranulosis, spongiosis and dyskeratosis. The dermis demonstrated a dense superficial perivascular interstitial lymphohistiocytic infiltrate without eosinophils. Given the clinical context, the findings were consistent with palmoplantar keratoderma (PPK) as an adverse effect of pembrolizumab. PPK is characterized by hyperkeratosis of the palms and soles, and can manifest as either an acquired or inherited condition. It is important for dermatologists to be aware of PPK as a paraneoplastic phenomenon and possible adverse effect associated with immune checkpoint inhibitors.