Watercolor drawing illustrating the eruption seen in pemphigus vegetans. This drawing shows the earliest lesions and was drawn from an area in the scapular region, on which a fresh crop of vesicles had recently appeared. Patches of thickened, deeply pigmented skin are also seen, representing older lesions. Walter Perceval Yetts, 1903. Pemphigus is a rare group of blistering autoimmune diseases that affect the skin and mucous membranes.