Bullous Pemphigoid Does Not Cause Cysts
Bullous pemphigoid causes tense blisters (bullae) and erosions, not cysts. The disease is characterized by subepidermal blister formation due to autoantibodies targeting BP180 and BP230 proteins in the basement membrane zone, resulting in fluid-filled bullae that are fundamentally different from cysts 1, 2.
Key Distinguishing Features of Bullous Pemphigoid Lesions
Tense blisters develop on erythematous or normal-appearing skin, typically on the limbs and trunk, and may be widespread or localized 1
The lesions are bullae (fluid-filled blisters), not cysts - histopathology shows subepidermal clefting with an inflammatory infiltrate mainly consisting of eosinophils 1
Pruritus alone or associated with erythema and/or urticarial plaques may precede bullae formation by weeks or months, and in some cases bullae may not become clinically apparent 1, 3
Bullae and/or erosions may occur in oral and genital mucosa, but these are still blistering lesions, not cystic formations 1
Pathophysiological Distinction
The mechanism involves autoantibody binding at the basement membrane zone followed by complement activation, which recruits inflammatory mediators leading to separation at the dermoepidermal junction and blister formation 2, 4
Cysts are epithelial-lined sacs containing fluid or semi-solid material, which is a completely different pathological entity from the subepidermal blistering seen in bullous pemphigoid 1
Clinical Pitfall to Avoid
Do not confuse tense bullae with cysts - while both may appear as raised, fluid-filled lesions, bullae are fragile blisters that rupture easily leaving erosions, whereas cysts are deeper, more stable structures 1, 5
If cystic lesions are present in a patient with suspected bullous pemphigoid, consider an alternative or concurrent diagnosis, as this would be atypical for BP 1