Rare association of pyoderma gangrenosum and palmoplantar pustulosis: a case report and review of the previous works.

Pyoderma gangrenosum is a rare inflammatory, ulcerative skin disease that mainly involves the lower extremities. It frequently occurs in association with systemic diseases such as inflammatory bowel disease, myeloproliferative disorders and rheumatoid arthritis. Palmoplantar pustulosis is also an inflammatory dermatosis characterized by recurrent sterile pustules localized on the palms and soles. These two dermatoses are histologically characterized by neutrophilic infiltration into the lesional skin. Co-occurrence of pyoderma gangrenosum and palmoplantar pustulosis in a single patient is extremely rare. We report a case of pyoderma gangrenosum occurred in a patient with palmoplantar pustulosis, with a review of the previously reported cases. A 68-year-old Japanese woman with a 10-year history of palmoplantar pustulosis developed a skin ulcer on the left lower leg. The ulcer was diagnosed as pyoderma gangrenosum based on the clinical and histological findings, and rapidly improved in response to oral prednisolone. In addition to our case, five cases with palmoplantar pustulosis who developed pyoderma gangrenosum have been reported. These cases were thought to have some characteristics in common, such as marked female predominance, no association with inflammatory bowel disease and myeloproliferative disorders, and good response to less aggressive therapy. The co-occurrence of pyoderma gangrenosum and palmoplantar pustulosis in our case may have an etiological link, rather than being a coincidental complication.