Discuss the pathogenesis of subcorneal pustular dermatosis.

The pathogenesis of subcorneal pustular dermatosis is unknown; although some cases have been associated with plasma cell dyscrasias. Even the nosology is controversial. While many authors accept this condition as a distinct entity, a few consider it to be synonymous with, or a variant of, pustular psoriasis. Histologically, both entities demonstrate a subcorneal vesicle filled with neutrophils. The strongest points against the relationship of subcorneal pustular dermatosis and psoriasis are that the former has a distinct clinical presentation, patients do not have preceding plaque-type psoriasis, and they are not likely to develop classic psoriasis during the course of their disease. Some drugs such as lithium carbonate may exacerbate subcorneal pustular dermatosis by increasing neutrophil migration into lesions.