Hypopyon sign: a half full or half empty scenario

The term "half-half blister" or the "hypopyon sign" refers to small vesicles that evolve into pustules, with the pus typically concentrating in the lower half of the vesicle. There is typically a transverse fluid level with purulent material at the bottom. This sign is usually not exclusive to a particular dermatological condition as it is seen in cases of subcorneal pustular dermatosis (Sneddon-Wilkinson disease), pyodermas and secondary infected vesicobullous disorders (such as pemphigus, bullous pemphigoid, and linear IgA dermatosis).