Three cases of subcorneal pustular dermatosis with immunohistochemical examinations

Abstract Subcorneal pustular dermatosis, a rare, benign skin disease, is a type of neutrophilic dermatosis. The authors reported three cases of subcorneal pustular dermatosis. In case 1, a 9‐year‐old girl developed a skin rash with blisters following a mycoplasma infection and had a flare‐up due to a common cold. She was successfully treated with a topical corticosteroid. In case 2, a 70‐year‐old woman who had been treated for rheumatoid arthritis with adalimumab, salazosulfapyridine, and leflunomide developed 3‐ to 5‐mm pustules on her trunk and thighs 4 days after flu vaccination. The rash disappeared with drug withdrawal and treatment with diaminodiphenyl sulfone. In case 3, an 81‐year‐old man, who was diagnosed with pyoderma gangrenosum at 61 years old, developed multiple small flaccid pustules on his trunk and extremities due to an infection in the arteriovenous shunt area on the forearm. The pustule disappeared with intravenous antibiotic therapy; however, the pustules subsequently flared up along with ulcers typical of pyoderma gangrenosum. He was given oral prednisolone therapy, which was effective for the small pustules and some ulcers. Immunohistochemical examination of the three cases revealed neutrophilic infiltration in the subcorneal layer of the epidermis. The pustules contained neutrophils as well as some CD68 + and a few CD1a + cells. The epidermis and dermis were more predominantly infiltrated by CD4 + cells than by CD8 + cells. Positive stainings for interleukin 8, interleukin 36γ, and phospho‐extracellular signal‐regulated kinases 1 and 2 were observed in the upper layers of the epidermis below the pustules. Although the pathogenesis of subcorneal pustular dermatosis has not been clarified, the current results suggest that a variety of inflammatory cells, including those responsible for both innate and acquired immunity, are involved in the accumulation of neutrophils in subcorneal pustular dermatosis.