• Pemphigus vulgaris is vulgar in that the blisters rupture and it's gross. + Nikolsky sign. (Its also more vulgar to use your mouth which is why only vulgaris has oral blisters.) Desmosomes are shot.

• bullous pemphigus is therefore not vulgar and doesn't pop = - Nikolsky sign. Hemidesmosomes are shot.

• lets rule everything else out for completeness

• Collagen type VII (i know wtf) = basement membrane btwn epidermis & dermis. NBME language synonyms = Basal Lamina, Reticular Lamina, Extracellular Matrix. Hemidesmosomes, which are made of integrin, fibronectin/laminin, bind to this collagen so it is close to correct but still wrong.

• cytokeratin is that intracellular intermediate filament in epithelial cells used in stains to distinguish cancers.

• Desmoplakin is apparently a part of desmosomes, which makes etymological sense. They are going for paraneoplastic pemphigus here. Sucks for them cuz we never learned that one haha. Gottem.

• Aside here--FA 2020 just mentions desmosomes are made from desmoglein I and III. Antibodies against desmoglein I and III are seen in pemphigus vulgaris and against I is seen in scalded skin syndrome from Staph aureus via exfoliative toxin AKA exfolitoxin. That is why both diseases are + Nikolsky. Good old nikolsky

• plakoglobin? nobody cares.

https://en.wikipedia.org/wiki/Nikolsky%27s_sign https://en.wikipedia.org/wiki/Desmoplakin https://en.wikipedia.org/wiki/Exfoliatin https://en.wikipedia.org/wiki/Plakoglobin

Bullous pemphigoid antigen must be hemidesmosome. FA: bulla are "bullow" the dermis (subepidermal blister). BP also yield "tense" bulla.

Bullous pemphigoid "Bull House" bulls are tough (BP do not rupture easily) and house reminds us of hemidesmosomes

Pemphigus vulgaris "Demphigus" for desmosomes

In bullous pemphigoid, autoantibodies are made against BPAg1 and BPAg2 found on hemidesmosomes.

"clear-fluid-filled, tense blisters" and "subepthelial blister" with "autoantibodies" scream bullous pemphigoid, but I thought BP blisters were itchy>>painful. Contrast with pemphigus vulgaris in which pain>>itch.