Subcorneal pustular dermatosis: 50 years on

We review the key developments in our understanding of subcorneal pustular dermatosis (SCPD, also known as Sneddon-Wilkinson disease) over the past 50 years. SCPD is a rare, chronic, sterile pustular eruption that was first described by Sneddon and Wilkinson in 1956. The primary lesions are pea-sized pustules classically described as half-pustular, half-clear flaccid fluid blisters. Histologically the salient feature is a subcorneal accumulation of neutrophils, suggesting the presence of chemoattractants such as tumour necrosis factor (TNF)alpha in the uppermost epidermis. However, to date its exact pathophysiology is unknown. Cases in association with pyoderma gangrenosum, benign monoclonal IgA gammopathy and multiple myeloma are well documented. There are anecdotal reports of SCPD associated with other internal malignancies such as chronic lymphocytic leukaemia, thymoma, apudoma and epidermoid carcinoma of the lung. The treatment of choice is dapsone. Therapeutic alternatives include retinoids, phototreatment with psoralen ultraviolet (UV) A, broadband or narrow band UVB and corticosteroids. Anecdotal uses of tacalcitol, ketoconazole, azithromycin, tetracycline, minocycline, vitamin E, ciclosporin, colchicine, mizoribine, mebhydrolin, infliximab and adalimumab with mycophenolate mofetil have all been reported.