Pruritis ani

'Unpleasant itching and burning of perianal skin'

• Typically worse at night or in warm, moist climates

Secondary pruritus ani

• Infectious
  • Bacterial
  • Fungal
    • Candida responsible for up to 15%
    • Especially in immunosupressed, on Abx, on steroids
    • Diffuse, erythematous, macerated plaques
    • Dermatophytes
    • Treat with topical or systemic antifungals
  • STI
    • Gonorrhoea
    • Chlamydia
    • Syphilis
  • Parasites
    • Esp nocturnal symptoms in children - pinworms
    • Scabies
    • Crabs
  • Viral
    • HSV
    • HPV - condyloma
    • HZ + shingles
• Anorectal
  • Chronic inflammation
    • Pilonidal disease
    • Perianal Crohns
    • Hidradenitis suppuritiva
  • Faecal contamination
    • Haemorrhoids
    • Fistula-in-ano
    • Anal fissures
    • Faecal incontinence
    • Skin tags
    • Chronic diarrhoea
• Dermatologic
  • Contact dermatitis
    • Ask about cleaning products/hygiene
  • Atopic dermatitis
    • Ask about other atopy
  • Perianal psoriasis
    • Scalp, flexor surfaces
  • Lichen sclerosis
    • • Commonly perimenopausal women, but can be associated with other autoimmune conditions
      • Probably also have vulvovaginal pruritis
      • Can give topical steroids - betamethasone topical (Diprosone 0.05%) daily for two weeks, then not more than twice a week to avoid skin atrophy
      • Barrier ointment like vaseline
      • Avoid harsh toilet paper, microtrauma of any form
      • Beware of malignant transformation into SCC - 5% lifetime risk
  • Seborrheic dermatitis
  • Radiation dermatitis
• Malignant
  • Anal canal cancer
  • Anal margin cancer
  • Rectal cancer
  • Bowen's disease
  • Extramammary Paget's (cutaneous adenocarcinoma in situ)
• Systemic disease
  • Diabetes
  • Leukaemia
  • Lymphoma
  • CKD (uraemia - only cure is kidney transplant)
  • IDA
  • Hyperthyroid
  • Hyperbilirubinaemia - ?cholestyramine

Idiopathic

• Diagnosis of exclusion
• Likely caused by faecal contamination leading to local irritation
  • Chronic diarrhoea
  • Poor hygiene or overzealous hygiene
  • Faecal incontinence
  • Mucus leakage
  • ?Pruritogenic foods
• 'Itch-scratch cycle' likely feeds into the chronic nature of this condition

History should be thorough

• Onset and duration
• Toileting behaviours
• Mucus leakage or perianal moisture
• Travel history
• Medications and allergies

Workup

• Biopsy suspicious lesions
• Bacterial and fungal swabs
• Tape test for pinworm?

Simple management suggestions

• Shower after opening bowels and pat dry with unscented TP
• If moist area, consider talc powder
• Treat any chronic diarrhoea with fibre supplements
• Avoid tight-fitting garments and perfumed products
• Try to avoid scratching
• Can trial topical steroids

Second-line therapy:

• Topical capsaicin (0.006%) TDS for 4 weeks - desensitises skin - seems to work up 70% of patients
• Topical tacrolimus has been tried
• Intradermal methylene blue - directly toxic to sensory nerves