A 36 year old male with history of psoriasis was staed on systemic steroids. After stopping treatment, the patient developed pustules in a generalized distribution. Gram stain from pustule showed only pus cells. The cause is most likely to be:

Generalized Pustular psoriasis is a rare and serious form of Psoriasis characterized by the sudden eruption of a large number of sterile pustules associated with fever. It is usually precipitated by infections, sudden withdrawal of steroids and pregnancy. The drug of choice is Methotrexate except in pregnancy where it is systemic steroids. Generalized pustular psoriasis in pregnancy is called Impetigo herpetiformis. Ref: Textbook of Dermatology By Rook, Volume 1, Page 19.34