© Springer-Verlag Berlin Heidelberg 2017Alexander Herold, Paul-Antoine Lehur, Klaus E. Matzel and P. Ronan O’Connell (eds.)ColoproctologyEuropean Manual of Medicine10.1007/978-3-662-53210-2_7
7. Perianal Skin Conditions
Department of Dermatology, St Vincent’s University Hospital, Elm Park, Dublin, Ireland
KeywordsPerianal dermatitisPruritus aniContact dermatitisHuman papillomavirus
Numerous dermatoses can affect the perianal skin. It is the author’s opinion that these conditions are best managed by a dermatologist in conjunction with a colorectal surgeon/gastroenterologist. Pruritus is the predominant symptom of perianal dermatoses and is itself a nonspecific symptom [1, 2]. A full dermatological history is required, including the duration of symptoms, the severity of pruritus if present, the history of skin disease, and a history of colonic/rectal disease. Detailed knowledge of the treatment used for the condition is needed, including perianal hygiene habits. A complete medical and surgical history is required, with appropriate questioning about medications, foreign travel, and sexual history. A full skin examination is also necessary. This allows the detection of inflammatory dermatoses that may also affect the perianal skin. The majority of perianal skin conditions can be diagnosed clinically; a skin biopsy is rarely helpful. Inflammatory dermatoses often require a clinicopathological correlation. There is an old adage in dermatology: if a clinician does not have any idea of the diagnosis, then a histopathologist rarely will be able to help.
7.1 Inflammatory Dermatoses
7.1.1 Perianal Dermatitis
This is the most common perianal dermatosis seen by dermatologists. It presents with perianal pruritus, which may be severe and occasionally painful. Sleep disturbance is common [1, 2]. Perianal dermatitis may be exacerbated by fecal leakage [1–3]. Patients may have a history of atopic dermatitis or contact dermatitis . Clinical examination often reveals a diffuse erythema of the perianal skin with lichenification and often excoriations.
Internal hemorrhoids can exacerbate perianal dermatitis, but perianal pruritus has rarely been reported in conjunction with rectal polyps and carcinoma . It is therefore recommended that all patients have a sigmoidoscopy, that internal hemorrhoids be appropriately treated, and any concurrent rectal pathology be reviewed.
All patients should be educated about appropriate hygiene. Most patients overclean the area with soaps, baby wipes, and/or excessive water. Soaps are an irritant that may exacerbate pruritus and inflammation. Patients with perianal dermatitis are at high risk for contact dermatitis from ingredients in soap, such as fragrances . Wet wipes often contain preservatives such as methylisothiazolinone, which are potent contact sensitizers  and should be avoided. Patients should be advised to clean the area once daily with only water and to dab the area dry avoiding excessive friction.
There is no evidence that dietary measures improve perianal dermatitis. Although it has been postulated that caffeine can reduce anal tone and perhaps increase anal leakage , there is no evidence that avoiding caffeine improves symptoms. This lack of evidence also applies to avoiding spicy foods, alcohol, and any other dietary manipulation. Given this lack of evidence, there seems to be little logic in recommending such interventions. Topical anesthetic preparations such as lidocaine or cinchocaine are ineffective for pruritus and should be avoided because there is a significant risk for contact sensitization .
There is evidence that chronic pruritus can result in reduced anal sphincter tone with microscopic leakage of fecal material after defecation . Feces are highly irritant to the skin and may exacerbate skin that is already inflamed. The use of a barrier cream such as zinc oxide after a bowel movement may prevent fecal material from irritating the perianal skin. Mild-potency topical steroids such as 1 % hydrocortisone ointment may be effective, especially when applied at night before sleep. One percent hydrocortisone does not cause skin thinning, unlike more potent topical steroids.
It is recommended that all patients undergo contact allergy testing or patch testing. Up to 30 % of patients with perianal dermatitis have a relevant contact allergy . Patients should be tested for several allergen series according to local protocols. In our centre, patients are tested to the British standard series, the fragrance series, the medicament series, the textile series, and their own leave-on products. The patches are applied on the back on Monday and read on Wednesday and Friday of the same week. Patch testing should only be done by medical and nursing staff who have appropriate training . The most common allergens in patients with perianal dermatitis are fragrances, preservatives such as methylisothiazolinone , and sodium metabisulfite , which are used in wet wipes and medicaments such as cinchocaine [2, 8]. Contact allergens may include nail varnish , topical steroids , and textile dyes . The majority of patients who are investigated and treated according to the above protocol achieve remission of their pruritus. Patients with more refractory disease may require more potent topical steroids, topical tacrolimus, and/or systemic antipruritic therapies.
7.2 Perianal Psoriasis
Psoriasis often affects the perianal skin. It can present with pruritus, bleeding, and/or perianal pain from fissuring. In these cases it is usually present in other areas, especially flexural areas including the genital region . This psoriasis is treated with mild-potency topical steroids or topical tacrolimus 0.1 % ointment. Severe perianal psoriasis may require treatment with systemic antipsoriatic agents such as methotrexate, fumaric acid esters, or tumor necrosis factor (TNF)-α inhibitors .
7.3 Lichen Sclerosus
Lichen sclerosus is an immune-mediated skin condition that results in skin atrophy and genital scarring . It is more common among women than men. It can affect the perianal skin, with resultant pruritus and pain, but is often asymptomatic. Upon clinical examination there are well-demarcated white/ivory plaques. Genital involvement is a given when the perianal skin is involved. Vulval lichen sclerosus can result in resorption of the clitoris, fusion of the labia minora, and urethral strictures. Long-standing lichen sclerosus can result in squamous cell carcinoma of the vulva and (rarely) perianal squamous cell carcinoma . Skin histology reveals characteristic findings of epidermal atrophy, homogenization of collagen with the formation of a cell poor Grentz zone in the upper dermis, and dermal fibrosis. Lichen sclerosus is treated with superpotent topical steroids such as clobetasol propionate ointment. This is highly effective in managing pruritus and in improving the histological features of the disease .
7.4 Hidradenitis Suppurativa
Hidradenitis suppurativa is a disease characterized by the development of painful nodules and abscesses commonly affecting the axillae, submammary area, inguinal folds, perineum, and perianal area . It is more common among women than men (3:1), smokers, and obese patients. There seems to be a genetic component in some patients; mutations of gamma secretase in familial hidradenitis suppurativa have been described . This disease significantly disturbs quality of life. Follicular occlusion seems to be the earliest abnormality in the pathogenesis of hidradenitis suppurativa, with subsequent abscess formation leading to sinuses and scarring. Perianal hidradenitis may present in isolation with recurrent nodules, abscesses that may develop into painful sinuses, fistulae, and scarring. The abscesses tend to be sterile. There is an association with Crohn’s disease . Skin histology may be of benefit in cases of diagnostic doubt.
The treatment of hidradenitis suppurativa involves both medical and surgical input. Medical treatments include the combination of oral clindamycin and rifampicin at a dosage of 300 mg of each drug twice daily for 10 weeks. In one series, up to 80 % of patients achieved remission with this combination . The main side effects of treatment are diarrhea and abnormal liver function test results. Oral tetracycline monotherapy and penicillins such as flucloxacillin seem to be ineffective. Topical clindamycin may be effective in some patients with mild disease. Intralesional triamcinolone has been reported as effective. Oral metformin and dapsone are used as second-line agents with moderate success. Inhibition of TNF-α with adalimumab has been demonstrated to be effective with 160 mg as a loading dose and 40 mg weekly. Over 40 % of patients achieve 50 % improvement . Infliximab has also been reported as an effective therapy for hidradenitis at a dosage of 5 mg/kg every 4 or 8 weeks. .
The best long-term results have been reported with surgery. Incision and drainage of recurrent abscesses do not result in improvement, and almost 100 % recur . Extensive excision of sinus tracts and fistulae offers the best hope for long-term remission. Excising sinus tracts with a Seton suture insertion delivers some success in patients with sinus tract disease.
The perianal skin is rarely affected in Crohn’s disease. It may present with perianal abscesses, similar to hidradenitis suppurativa. It may be contiguous with lower-bowel Crohn’s disease or associated with perineal fistulae, or be separate (so-called metastatic Crohn’s disease). The treatment of cutaneous Crohn’s disease is difficult. The best results have been achieved with topical superpotent and/or intralesional steroids in combination with TNF-α inhibition with adalimumab or infliximab . Surgical excision is ineffective.