Background: Overlap of bullous pemphigoid (BP) with chronic psoriatic plaques (CPP) is a common condition. However, the association of BP with pustular psoriasis (PP) is uncommon. Moreover, perilesional erythema and pustular lesions on CPP are accepted as a sign of unstable psoriasis. Unstable psoriasis could be triggered by certain irritant topical treatments against psoriasis. These chemical agents could also induce a localized pattern of generalized PP. Here, we describe BP and PP collision in unstable CPP. Objective: By this observation we suggest that BP could be a sign of active psoriasis. Presumably, psoriasis-induced BP is an inflammation activity-dependent condition. Methods: This study is a case report and literature review. Results: The dramatic response of bullo-pustular lesions to short-term methotrexate (MTX) treatment suggests the rule of ‘no psoriasis, no BP'. Presumably, MTX supressed the active inflammation of CPP and BP disappeared following CPP control. Conclusion: BP can be a sign of active psoriasis in the present case.