GPAtlas🧭 When to suspect
Pruritus ani – itching of the perianal skin – is a symptom, not a diagnosis. Find and treat the cause before labelling it idiopathic (no identifiable cause).
• It is common, affecting up to 5% of people.
• It is around four times more common in men.
• It typically presents between the ages of 40 and 60.
The itch is characteristically worse at night and after defecation. It is perpetuated by three things:
• The itch–scratch cycle.
• Minor faecal soiling.
• Often the very soaps, wipes and creams used to treat it.
Most cases (roughly half to nine in ten) are idiopathic, but a secondary cause must always be sought.
The two clinical priorities are therefore: identify and remove the underlying cause and irritants, and never miss an anorectal malignancy or premalignant lichen sclerosus presenting as a persistent itch.
| Category to exclude | Examples |
|---|---|
| Dermatoses | Eczema/dermatitis (irritant or allergic contact), flexural psoriasis, lichen sclerosus, lichen planus, seborrhoeic dermatitis |
| Infections/infestations | Threadworm (pinworm), candida, dermatophyte (tinea), perianal streptococcal dermatitis, anogenital warts, herpes simplex (HSV), sexually transmitted infections (STIs) |
| Anorectal | Haemorrhoids, anal fissure, fistula, skin tags, rectal prolapse, faecal soiling or incontinence |
| Systemic | Diabetes mellitus, thyroid and liver disease, chronic kidney disease, haematological disorders (e.g. lymphoma) |
| Premalignant/malignant | Lichen sclerosus, anal squamous cell carcinoma, extramammary Paget disease |
| Idiopathic/perpetuating | Itch–scratch cycle, overzealous cleaning, fragranced wipes and soaps, dietary irritants, occult faecal leakage |
Source: DermNet
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