A case study of a subcorneal pustular dermatosis in a 27-years-old female patient is reported. Here we provide historical information and describe current understanding of the etiology, pathogenesis, clinical presentation, treatment, as well as the differential diagnosis of a rare dermatosis, Sneddon—Wilkinson disease. The results of histological examination of biopsy sample, which revealed formation of subcorneal pustules containing neutrophils, lymphocytes, and fibrin, are reported. The bottom of pustules is formed by granular layer. Edema, perivascular infiltration with lymphocytes, histiocytes, and small amounts of neutrophils infiltrating the epidermis were observed in the upper dermal layers. Immunofluorescence studies revealed no IgA antibodies to epidermal cells. It was shown that comprehensive treatment of the disease with diaminodiphenylsulfones and topical corticosteroids led to regression of cutaneous process. Modern histopathological and immunofluorescence studies (direct and indirect method) aimed at detecting IgA antibodies to epidermal cells play a key role in formulation of correct diagnosis.