- Intense anal/perianal itching and/or burning
- Usually acute (defined as <6 weeks of symptoms)
- Classified as primary (idiopathic) or secondary (25–75% of cases) to anorectal pathology
- 1–5% of the general population
- Predominant age: 30 to 50 years; although seen in all ages groups
- Predominant sex: male > female (4:1)
Difficult to estimate because many patients do not report symptoms; affects 1–5% of the population
Etiology and Pathophysiology
- Multiple etiologies categorized by inflammatory, infectious, systemic, neoplastic, anorectal disorders, neuropathic, neurogenic, and psychogenic causes (1),(2)
- Most cases are idiopathic (25–90%), which are likely due to trauma from wiping or scratching and perianal fecal contamination.
- Soilage can be due to an abnormality of rectoanal inhibitory reflex and a lower threshold or transient internal anal sphincter relaxation.
- Depending on underlying etiology, itch pathway may be histamine mediated or nonhistamine mediated (1).
- Pruritus ani is typically intensely perceived by the patient due to dense innervation.
- Etiologies of secondary pruritus ani:
- Inflammatory dermatologic diseases:
- Allergic contact dermatitis (soaps, perfumes, or dyes in toilet paper, topical anesthetics, oral antibiotics)
- Atopic dermatitis ± lichen simplex chronicus (Patients also have asthma and/or eczema.)
- Psoriasis (Lesions tend to be poorly demarcated, pale, and nonscaling.)
- Seborrheic dermatitis
- Lichen planus (may be seen in patients with ulcerative colitis and myasthenia gravis)
- Hidradenitis suppurativa
- Radiation dermatitis (2)
- Colorectal/anorectal diseases: rectal prolapse, hemorrhoids, fissures or fistulas, proctitis, chronic diarrhea/constipation, polyps
- Infectious etiologies may be sexually transmitted: bacteria (gonorrhea, chlamydia, syphilis), viruses (herpes simplex virus [HSV], condyloma acuminate from human papillomavirus [HPV], molluscum), parasites (pinworms, lice, scabies, or bed bugs), fungal (Candida, or dermatophytes like tinea); other bacteria (Staphylococcus aureus, β-hemolytic Streptococcus, Corynebacterium minutissimum [erythrasma]) (2)
- Malignancies: melanoma, basal cell/squamous cell carcinoma, colorectal cancer, leukemia, lymphoma, or (uncommon) the presenting symptom of Bowen or Paget disease
- Mechanical factors: vigorous cleaning and scrubbing, tight-fitting clothes, synthetic undergarments
- Systemic diseases (often presents as generalized pruritus): diabetes mellitus (most common), cholestasis, chronic liver disease, renal failure, hyperthyroidism, anemia, HIV, vitamin or iron deficiencies, lumbosacral radiculopathy (particularly in the elderly)
- Chemical irritants: local anesthetics, chemotherapy, diarrhea (often from antibiotic use)
- Dietary elements (citrus, milk products, coffee, tea, cola, chocolate, beer, wine, tomatoes, nuts)
- Psychogenic factors: anxiety–itch–anxiety cycle
- Inflammatory dermatologic diseases:
- Excess perianal hair growth and/or perspiration
- Underlying anorectal pathology
- Atopic disease
- Underlying anxiety disorder
- Caffeine intake has been correlated with symptoms.
- Good perianal hygiene; avoid overzealous cleaning.
- Avoid mechanical irritation of skin (vigorous cleaning or rubbing with dry toilet paper or baby wipes, harsh soaps or perfumed products, excessive scratching with fingernails, or tight/synthetic undergarments).
- Minimize moisture in perianal area (absorbent cotton in anal cleft may help keep area dry).
- Avoid laxative use (loose stool is an irritant).
Commonly Associated Conditions
- Psoriasis is seen in 5–55% of patients with pruritus ani.
- Coexisting anorectal disease, such as hemorrhoids, can be seen in up to 52% of patients with pruritus ani.
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