Evaluation of pustular rash

Last reviewed: June 2020

Last updated: June 2018

A pustular rash is defined as the occurrence of a rash that is composed of pustular lesions. A pustule is a vesicle or bulla containing purulent material. It varies in size and may occur at different levels within the epidermis: subcorneal, intraepidermal, or basement membrane zones.

When the pus is contained within the dermis, the lesion is called an abscess or furuncle. If it is deep and dissects through tissue planes it is called a carbuncle. The pustules may or may not be sterile and are normally filled with neutrophils.

This monograph covers purely pustular rashes as well as vesicular eruptions that develop into pustular rashes.

Differentials

Common

Impetigo
Folliculitis caused by Pseudomonas
Folliculitis caused by Staphylococcus aureus
Pityrosporum folliculitis
Herpes simplex virus
Dermatophytosis: tinea barbae
Dermatophytosis: tinea cruris
Dermatophytosis: tinea pedis
Dermatophytosis: tinea corporis
Acne vulgaris
Eosinophilic folliculitis (Ofuji syndrome/disease)
Subcorneal pustular dermatosis (Sneddon-Wilkinson disease)
Infantile acropustulosis (IA)
Fire ant bites
Acrodermatitis continua (pustular acrodermatitis, acrodermatitis continua suppurativa Hallopeau, dermatitis perstans, and dermatitis repens Crocker)
Pustular drug rash secondary to epidermal growth factor receptor (EGFR) inhibitors
Acute generalized exanthematous pustulosis (AGEP)
Generalized pustular psoriasis (von Zumbusch type)
Transient neonatal pustular melanosis
Pustulosis palmaris et plantaris (PPP)