1.7 Pustula (Pustule)

Pustule.

Superficial intraepidermal collection of cloudy or pus-laden fluid in the epidermis, follicular or acrosyringal opening.

Color: yellow.

Size: < 5 mm.

May appear anywhere on body, often associated with hair follicle.

Disseminated involvement of hair follicles = folliculitis.

Disseminated involvement of acrosyringia.

May develop crusts or erosions.

Associated with vesicles and bullae.

Sterile pustule (neutrophilic collections in pustular psoriasis), purulent contents (staphylococcal folliculitis).

• Pustular skin manifestations of viral, bacterial and fungal diseases.

• There are various forms of pustular psoriasis (see chapter on psoriasis): generalized pustular psoriasis (von Zumbusch) and its atypical forms, erythema anulare centrifugum-like psoriasis with and without pustulation (EACP); psoriasis vulgaris with pustulation; palmo-plantar pustular psoriasis (Königsbeck-Barber) and its acral variant; acrodermatitis continua suppurativa (Hallopeau), and transitional forms.

• Acute generalized exanthematous pustulosis (AGEP): severe cutaneous adverse reaction, mostly due to antibiotic drugs. It is characterized by the rapid development of nonfollicular, sterile pustules on an erythematous base. Acute onset of fever and pustulosis with leukocytosis within 24 hours. Mucous membranes and internal organs may be involved. Dermatopathology shows intracorneal, subcorneal, and/or intraepidermal pustules with papillary dermal edema containing neutrophils and eosinophils. Treatment besides cessation of the causative drug includes topical or systemic glucocorticosteroids.

• SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome is a is an autoinflammatory syndrome showing osteoarticular and dermatological manifestations, characterized by mainly by palmoplantar pustulosis and severe acne.

Treatment with nonsteroidal anti-inflammatory and antirheumatic drugs.

• Pustulosis palmaris et plantaris (PPP) is a  distinct entity of unclear pathomechanism, occurring preferentially in Japan. It shows vesicles, pustules and erythema. Its pathomechanism is not clear. Monoclonal antibody against interleukin (IL)-23 has been employed for treatment.

• Miliaria crystallina, rubra, or profunda are caused by blocked eccrine sweat glands and ducts on different levels. They result in self-limited rashes with vesicles.

• Erythema toxicum neonatorum and the transient neonatal pustular melanosis (TNPM, more common in black newborn) probably are different clinical expressions of the same entity. They are self-limiting and do not need a specific treatment.

• Diaper dermatitis (see 1.1.2.6 Napkin dermatitis).

• Various forms of pustular acne (see 4.1.1 Acne).

Loss of adhesion of epidermal keratinocytes caused by infectious agents (herpes simplex virus, Staphylococcus aureus) inflammation or autoimmune mediated reactions.