An Infant with Widespread Pustules
A 3-week-old girl is brought with a 5-day history of crops of small pustules on the trunk, limbs and scalp, with some erythematous papules. She is otherwise well, feeding normally, afebrile, and gaining weight. There is no mucosal involvement and no palmoplantar lesions. Mother had no rash during pregnancy. A Gram stain of pustule contents shows neutrophils but no organisms; bacterial culture is sterile. You are asked to see her in the outpatient clinic and to decide whether she needs admission, antibiotics, or investigation for immunodeficiency.
1. What is the differential diagnosis and how would you distinguish the likely entities clinically?
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Differential of neonatal pustular eruption in a well infant:
- Erythema toxicum neonatorum - usually first 48–72 h, blotchy erythema with central yellow-white papule/pustule, eosinophils on smear; this infant is 3 weeks old, so less likely.
- Transient neonatal pustular melanosis - present at birth, pustules that rupture leaving collarettes of scale and hyperpigmented macules; not this history.
- Neonatal acne - inflammatory papules/pustules on face and upper trunk, usually from 2–4 weeks; no organisms.
- Miliaria pustulosa - heat-related, in skin folds, obstructed eccrine ducts.
- Candidal pustulosis - usually with oral thrush and nappy rash; KOH shows pseudohyphae.
- Staphylococcal pustulosis/impetigo - Gram stain/culture usually positive; infant may be unwell.
- Eosinophilic pustular folliculitis of infancy - pruritic recurrent crops, peripheral eosinophilia.
Distinguishing features: distribution and timing; presence of systemic illness; Gram stain and culture; KOH; and response to environmental measures. A well, afebrile infant with sterile pustules and no mucosal disease favours a benign self-limiting eruption.
2. The lesions persist and new crops appear over 6 weeks. What investigations and management would you consider, and when would you worry about immunodeficiency?
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Investigations:
- Skin swabs and pustule contents for Gram stain, bacterial and fungal culture, and KOH for Candida.
- Blood: full blood count with differential (eosinophilia supports eosinophilic pustular folliculitis), CRP, and if recurrent infection is a concern, immunoglobulin levels, lymphocyte subsets, neutrophil oxidative burst and HIV testing.
- Consider skin biopsy if lesions are atypical or persist despite treatment - histology may show folliculitis with eosinophils.
Management:
- Reassurance and supportive care for benign eruptions; avoid unnecessary antibiotics.
- If staphylococcal infection is confirmed, topical or oral antistaphylococcal therapy as appropriate.
- For eosinophilic pustular folliculitis of infancy, topical corticosteroids or topical calcineurin inhibitors may help; it usually resolves by 1–2 years.
- Review feeding, growth and development at each visit.
When to suspect immunodeficiency: recurrent or severe infections, failure to thrive, persistent candidiasis, unusual organisms, family history, or pustules that do not resolve and are associated with systemic illness. In a thriving, afebrile infant with sterile pustules, immunodeficiency is unlikely, but persistent or recurrent infection warrants the immunological screen above.