An unusual cause for a psoriasiform dermatosis

A 79-year-old woman presented with a 5-month history of a painful dermatosis affecting her hands and feet. This developed into inflammation with fissuring, affecting the fingers and toes. The patient was a current smoker with a 65-pack-year history. She had no other medical conditions, no respiratory symptoms and was otherwise systemically well. On physical examination, striking nail changes were seen. There was marked subungual hyperkeratosis on the hands and brown discolouration of the nails, with detachment from the nail bed and loss of the cuticle (Fig. 1a), as well as significant involvement of the toes (Fig. 1b). Examination of the soles revealed marked confluent hyperkeratosis (Fig. 1c). Although the primary site of involvement was acral, there was also a diffuse macular erythema of the legs. Laboratory investigations showed erythrocyte sedimen-tation rate of 49 mm/h (normal range 0–30 mm/h), but were otherwise unremarkable. Chest radiography revealed a subtle lesion projected over the seventh posterior rib. The patient subsequently underwent computed tomography (CT) of the chest followed by positron emission tomography (PET)-CT, which showed a metabolically active nodule in the right upper lobe (Fig. 2a) that was highly suspicious for lung malignancy. The patient went on to have a right upper lobec-tomy of the lung, making a full postoperative recovery. Following tumour resection, the dermatosis significantly improved (Fig. 2b). Histological findings Following lung resection, an incisional biopsy taken from the sole of the foot showed parakeratosis and lymphocyte exocytosis, with a psoriasiform spongiotic dermatitis (Fig. 3). Histology from the lung lesion confirmed an underlying diagnosis of squamous cell carci-noma (SCC). What is your diagnosis? (a) (b) (c) Figure 1 (a) Striking changes of the fingernails and (b) toenails, and (c) marked confluent hyperkeratosis of the soles.