Pustules
Differential Diagnosis
Common Diagnoses
- Impetigo
- Other Staphylococcal Infections (e.g. Early Boils, Folliculitis, Sycosis Barbae)
- Acne Vulgaris
- Rosacea
- Herpes Simplex
- Herpes Zoster
Occasional Diagnoses
- Perioral Dermatitis
- Hidradenitis Suppurativa (Axillae and Groins)
- Candidiasis (Satellite Vesicopustules Around Moist Eroded Patch)
- Pustular Psoriasis (Palmar and Plantar Commoner Than Generalised Pustular Psoriasis of Von Zumbusch)
Rare Diagnoses
- Dermatitis Herpetiformis
- Behçet’s Syndrome
- Viral: Cowpox and Orf (Note: Chickenpox is Vesicular, Not Pustular)
- Hot Tub Folliculitis (Superficial Pseudomonas Infection)
- Drug Induced
Ready Reckoner
Key distinguishing features of the most common diagnoses
| Impetigo | Other Staphylococcal Infections | Herpes Simplex or Zoster | Acne Vulgaris | Rosacea | |
|---|---|---|---|---|---|
| Grouped or Single | Possible | Possible | Yes | No | No |
| Staphylococcal | Yes | Yes | No | No | No |
| Recurrent | No | Possible | Possible | Yes | Yes |
| Affects Eye | No | No | Possible | No | Possible |
| Tingling before Lesion | No | No | Yes | No | No |
Possible Investigations
- There are very few investigations likely to prove useful or necessary in primary care. The presence of widespread or recurrent candidal or staphylococcal lesions might necessitate a urinalysis or blood sugar/HbA1c to exclude diabetes; a swab of pus may help confirm a clinically suspected infective agent; and in very obscure cases, a skin biopsy might prove helpful.
Top Tips
- Take time to explain to the patient the nature of the problem in recurrent staphylococcal infections. Exclude diabetes, check carrier sites and reassure that the patient’s ‘hygiene’ is not in question. A prolonged course of antibiotics may be helpful.
- Check self-treatment in rosacea and perioral dermatitis. Treatment with OTC topical steroids will exacerbate the problem. Warn the patient that the condition may worsen before it improves on withdrawal of this inappropriate treatment.
- Papules and pustules around the mouth and eyes, often with a halo of pallor around the lip margin, are caused by perioral dermatitis. Treat with antibiotics, not topical steroids.
Red Flags
- Widespread, severe and recurrent staphylococcal lesions suggest diabetes or possible immunosuppression.
- Localised pustular psoriasis can be very resistant to standard treatments, so have a low threshold for referral. The very rare generalised form can make the patient dangerously ill – admit urgently
- Remember that herpes simplex or zoster infections in the immunocompromised can become disseminated and severe.
- Ocular problems in rosacea can be complicated and troublesome – refer to an ophthalmologist.