Hypopyon sign in pemphigus vulgaris

A 30-year-old lady was hospitalized with a five-month history of oral erosions and a generalized vesiculobullous eruption. Some of these blisters had a layer of pus at the bottom, sharply separated from clearer fluid on top, showing the so-called “hypopyon sign” [Figure 1]. Skin biopsy demonstrated a ‘row of tombstones’ appearance of the epidermal basal layer along with several acantholytic cells. Direct immunofluorescence examination showed epidermal intercellular IgG deposits, confirming the diagnosis of pemphigus vulgaris.

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Figure 1:

Several blisters on the abdomen with a layer of pus at the bottom and serous fluid on top (hypopyon sign)

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“Hypopyon sign” or “half-half blister” describes small vesicles that turn pustular with pus characteristically accumulating in the lower half of the vesicle. It is better appreciated when the patient stands upright. Standard texts generally mention the hypopyon sign only in the context of subcorneal pustular dermatosis.¹ However, it is important to remember that this sign may not be specific to a particular disease, but can be seen in several bullous disorders as a result of the ongoing inflammation.²