Papules
Differential Diagnosis
Common Diagnoses
- Acne
- Scabies
- Viral Wart and Molluscum Contagiosum
- Campbell De Morgan Spot
- Skin Tag
Occasional Diagnoses
- Viral Illness
- Milia
- Insect Bites
- Early Seborrhoeic Wart
- Xanthomata
- Guttate Psoriasis
- Pityriasis Lichenoides Chronica, Lichen Planus
- Prickly heat
- Keratosis Pilaris
Rare Diagnoses
- Malignant Melanoma, Early Basal Cell Carcinoma, Kaposi’s Sarcoma
- Darier’s Disease
- Acanthosis Nigricans
- Pseudoxanthoma Elasticum
- Tuberous Sclerosis
Ready Reckoner
Key distinguishing features of the most common diagnoses
| Acne | Scabies | Viral Wart | C. de M. Spot | Skin Tag | |
|---|---|---|---|---|---|
| Itchy | No | Yes | No | No | No |
| Characteristic Distribution | Yes | Yes | No | Yes | No |
| Red | Yes | Yes | No | Yes | No |
| Associated Lesions | Yes | Yes | No | No | No |
| History of Contact | No | Yes | Possible | No | No |
Possible Investigations
- In practice, very few investigations are needed with this presentation: A lipid screen is required in the presence of xanthomata; genital warts require referral for screening for other STDs; thorough investigation may be needed in the very rare case where underlying malignancy is possible (e.g. acanthosis nigricans); and obscure rashes or solitary papules may occasionally require excision biopsy for a definitive diagnosis.
Top Tips
- Bear in mind that skin cancer is usually uppermost in the patient’s mind, especially in subacute or chronic cases – so provide appropriate reassurance.
- In obscure solitary lesions, record clinical findings carefully and arrange to review in due course.
- Itchy, asymmetrical grouped papules are likely to be insect bites, although the patient may take some convincing!
Red Flags
- An enlarging dark blue or blue-black papule may be a malignant melanoma, blue naevus or Kaposi’s sarcoma. Refer for urgent opinion.
- Brown, skin-coloured papules crowded around the nose of a child may be tuberous sclerosis. This can be associated with serious systemic pathology so refer for expert opinion.
- An intensely itchy papular rash which is worse at night and has no other obvious cause is likely to be scabies, even if scabetic burrows are not evident – treat on suspicion.