Papules
Papules are solid, circumscribed skin elevations up to 5 mm in diameter. If they are larger, they are called nodules – these are dealt with elsewhere (see ‘Nodules’). (Clearly, many nodules start life as a papule; to avoid confusion, if they are generally ‘nodular’ by the time they present , then they are dealt with in that section, and not repeated here.) They are usually round but the shape, and the colour, may vary. They may be transitional lesions, e.g. becoming vesicular, or about to ulcerate. NOTE: There are more causes of papules than can be listed here. This is a sensible selection.
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.