Pustular skin conditions

What are pustules?

Pustules are smaller than 5–10 mm, and filled with pus, that is, purulent material composed of inflammatory cells (neutrophils).

• Pus can indicate bacterial, fungal or viral infection
• Some pustules are sterile and are due to inflammatory skin disease

This topic provides a differential diagnosis of pustular skin conditions.

• Acute mainly pustular generalised eruptions
• Acute mainly pustular localised eruptions
• Chronic mainly pustular eruptions

Acute mainly pustular generalised eruptions

Generalised pustular psoriasis

• Febrile illness
• Annular plaques studded with pustules

Acute generalised exanthematous pustulosis

• Febrile illness
• Drug eruption
• Diffuse superficial pustules

Acute mainly pustular localised eruptions

Impetigo

• Rapidly enlarging plaque
• Swab Staphylococcus aureus +/- Streptococcus pyogenes

Furunculosis/boil

• Based on hair follicle
• May lead to abscess formation
• Swab Staphylococcus aureus

Folliculitis

• Itchy or painful follicular pustules
• Various types

Dermatophyte infection

• Kerion: abscess formation
• Due to zoophilic fungus, eg Microsporum canis

Thrush

• Intertrigo, oral mucosa
• Superficial pustules that dry out easily
• Swab Candida albicans

Miliaria

• Sweat rash

Chronic mainly pustular eruptions

Acne

• Face, neck, upper trunk
• Comedones + inflammatory lesions

Acneform eruptions

• Rosacea
• Periorificial dermatitis
• Chronic folliculitis

Rosacea

Perioral dermatitis

Spa pool folliculitis

Scabies

• Irregular pustules on hands and feet
• Burrows between fingers, volar wrists
• Papules axillae, groin
• Generalised itchy rash

Dermatophyte infection

• Irregular annular plaque with peripheral scale
• Pustules on feet due to Trichophyton interdigitale

Localised pustulosis

• Hands, feet
• Sterile tender, itchy, pustules

Erosive pustular dermatosis

• Sun damaged scalp
• Often, underlying squamous cell carcinoma
• Greenish pus
• Culture Staphylococcus aureus