Eczematous lesions in the anogenital area may be caused by allergic and irritant contact dermatitis, seborrhoeic dermatitis and atopic dermatitis. In practice, it is often difficult to settle for a single etiologic factor, as an overlapping of endogenous factors (e.g. atopic dermatitis) and exogenous factors (irritant or allergen) is quite common. Allergic contact dermatitis is often due to topical medications such as neomycine, local anaesthetics, ethylenediamine and haemorrhoid creams, to medicated toilet paper and sprays.
Clinical picture: Depending on the acuity of the lesions clinical features vary from erythema, oozing, erosions, fissures and excoriations to gross lichenification. Burning, stinging or itching are often present.
Diagnosis: The diagnosis is based on careful history taking to identify possible irritants or allergens and a total-body dermatological examination. Bacterial and mycological cultures are recommended to exclude superimposed infections. Patch testing should be performed if allergies are suspected. A skin biopsy may be helpful in excluding other diagnoses mimicking eczema.
Differential diagnoses: Anal and perianal lesions: Inverse psoriasis, intertrigo, mycosis, extramammary Morbus Paget, syphilis and histiocytosis X are possible differential diagnoses. Genital lesions in females: Psoriasis, lichen ruber vulvae, vulvovaginitis gonorrhoica, lues stage II, erysipelas and candidiasis must be taken into account. Genital lesions in males: Various forms of balanitis, erysipelas, lues stage II, psoriasis and erythroplasia Queyrat are possible differential diagnoses.