Causes and Management of Pruritus Ani

CASE SUMMARY: A 48-year-old healthy man presented to the office reporting a long-standing history of anal pruritus. He had tried various over-the-counter creams without much success. Besides an anal fissure in the past, which responded to nitroglycerin ointment, his medical history was unremarkable. On physical examination, he was found to have grade I hemorrhoids and mild fecal smearing on perianal skin. Recent colonoscopy and laboratory work ordered by the primary care provider were normal. He was counseled on common inciting agents and local irritants and was advised on hygiene, diet modification, and stool-bulking agents. The colorectal surgeon recommended that the patient keep a journal about his symptoms, foods, and household chemicals used. He was seen twice more over the course of 6 months to pinpoint the cause of his pruritus. A short-course trial of topical steroid, barrier cream, and topical tacrolimus was not helpful. A biopsy of perianal skin was performed and was unrevealing. Eventually, given the persistence of symptoms, it was decided that he would undergo methylene blue injection to address his pruritus (Fig. 1). The procedure consisted of several intradermal and subcutaneous injections of 10 mL of 1% methylene blue combined with 7.5 mL of 0.25% bupivacaine with adrenaline (1/100,000) and 7.5 mL 0.5% lidocaine. After the methylene blue injection, the severity of his symptoms improved, but pruritus still persisted. A methylene blue injection of the same concentration was repeated in 3 months with complete resolution of symptoms.