21 Atopic Dermatitis (Atopic Eczema, Disseminated Neurodermatitis, Besnier’s Prurigo) INTRODUCTION Atopic dermatitis is the cutaneous component of a complex hereditary predisposition that also includes a tendency toward bronchial asthma and immediate type I allergy to a range of environmental antigens manifest by allergic conjunctivitis. The linkage among the three is poorly understood but with careful history taking, 75 to 80% of patients are found to have a positive family history. Atopic dermatitis is a multifaceted problem and exhibits diverse physiological defects, which continue to lead investigators in many different directions. Among the more prominent features, there is evidence of a functioning, but disordered, immune system that overreacts through humoral mechanisms to common environmental antigens (pollen, danders, foods, house dust), while responses of the delayed or cellular immune system to certain antigens (toxicodendron, candida, tuberculin, and some viruses) are depressed. This defect of immune modulation is clinically manifest by abnormal handling of certain otherwise minor infections. Other features include inherently dry skin, altered vasomotor responses, and disturbed sweating with sweat retention. It is beyond the scope of this book to discuss the complex interactions in atopic der- matitis, but the practitioner must be aware of their existence, as they can be important in the recognition and treatment of certain cases. CLINICAL APPLICATION QUESTIONS A 68-year-old retired bank executive seeks your help regarding a progressively dis- abling and intensely pruritic rash that has generalized over the past 6 months. Examination reveals a widespread inflammatory dermatitis with excoriations and impetiginization. Heavily involved areas include the face, neck, upper back, scalp, and the dorsum of the hands. The margins of the eruption are indistinct and the neck and flexures are more heav- ily involved with secondary changes of lichenification. You consider a diagnosis of late- onset atopic dermatitis. 1. What historical information might help to support the diagnosis? 2. Are there any ancillary physical findings that support your diagnosis? 3. What is the most important consideration in the differential diagnosis of late-onset atopic dermatitis? 4. What supporting laboratory data are indicated? 5. Assuming a diagnosis of adult-onset atopic dermatitis, how would you approach treatment? From: Current Clinical Practice: Dermatology Skills for Primary Care: An Illustrated Guide D.J. Trozak, D.J. Tennenhouse, and J.J. Russell © Humana Press, Totowa, NJ 199 200 Part IV / Epidermal, Dermal, Eczematous Lesions, Atrophies APPLICATION GUIDELINES Specific History Onset Atopic dermatitis can begin at any age, but onset early in life is the rule. Approxi- mately 10% of infants are affected and 75% of cases begin within the first 6 months. The vast majority of cases are manifest by puberty, and those that begin in middle life or beyond are so unusual that the diagnosis must be carefully established to rule out other entities such as cutaneous T-cell lymphoma. Evolution of Disease Process This is a chronic disorder that is subject to exacerbations and remissions. Although there are exceptions, most cases tend to gradually remit with advancing age. The disorder is divided into three clinical phases, and the last two show considerable overlap. Infantile atopic dermatitis: This usually starts during the second to sixth month on the cheeks and spreads to involve the scalp and then other regions. As the infant begins to crawl, it is common for the lesions to localize to areas of friction on the knees, elbows, and the extensor surfaces of the limbs. The diaper area is almost always spared. Mild cases are often completely controlled with modest amounts of topical medication while more severe cases are subject to periodic flares. Between the second and third years, about half the cases go into remission, while the rest evolve into the childhood phase. Childhood atopic dermatitis: Some of these cases occur without an antecedent infantile phase. The skin lesions remain intensely pruritic but assume the more character- istic lichenified appearance considered to be the hallmark of the disease. The distribution also changes so that the flexures of the limbs, the neck, and the wrists and ankles are prominently involved. Adult atopic dermatitis: Prominent involvement of the face, neck, upper chest, flex- ures, and hands occurs with lesions that are similar to those of the childhood type. Typically the disease becomes more localized during adulthood, so that only very focal lesions may remain active. Local atopic dermatitis may develop in an adult for the first time or the disorder may recur in this form following years of remission after infancy. Sites of local predilection include the scalp, hands, vermilion of the lips and immedi- ate perioral skin, upper and lower lids, nipples and areolae, and the vulva. These limited sites will remain active for years, but are responsive to topical therapy. With treatment, long-term or permanent remission is not unusual. Photosensitivity occurs in a small num- ber of adult atopics, but is not encountered in the infantile or childhood phases. Complications include the following: 1. Kaposi’s varicelliform eruption. Originally two variants were described. • Eczema vaccinatum has not been seen since the discontinuation of smallpox vaccinations. This dread complication may return again unless a safer killed vaccine is developed for prevention of terrorist attacks. • Eczema herpeticum is a generalized cutaneous infection with herpes simplex virus often accompanied by high fever and systemic toxicity. Deaths have Chapter 21 / Atopic Dermatitis 201 occurred in the past when there was no effective treatment. Papulovesicular lesions are widely superimposed upon the eczema, which promptly worsens. A Tzanck smear or RIF test for herpesvirus should rapidly confirm the diagnosis so that systemic antiviral therapy for herpes can be initiated. There is at present no proven antiviral agent for vaccinia virus. 2. Anterior and posterior subcapsular cataracts have been reported. These were doc- umented prior to the advent of corticosteroid therapy. Symptomatic lesions are uncommon. Evolution of Skin Lesions The lesions of the infantile phase are less defined than those seen later on. Poorly demarcated erythema develops with intensely pruritic papules and papulovesicles. The itching is so intense that the papular lesions are rapidly excoriated and are seldom seen intact. Usually the surface is moist and exudative from excoriations when the infant first presents. Scalp involvement in infants presents with diffuse, loose white scale over a base of erythema. As the infant enters the childhood and adult phases, the involved areas become drier and lichenified with the skin markings characteristically accentuated. Excoriated papules, however, are often still evident. In general, lesional sites become more focal but margins of lesions remain indistinct. Special sites of involvement include the following: Lips. Vermilion and perioral eczema with persistent lip licking is almost always a manifestation of atopy. An acute contact allergy must be considered, and appropriate his- tory should be taken regarding cosmetics (lipsticks, pomades, etc.) and foods (mango, cashews, etc.). In the atopic patient, wrinkling and lichenification are prominent features, while true contact reactions, in the authors’ experience, are more acute and vesicular (see Photo 29). Hands: Chronic dermatitis on the dorsum of the hands and digits is common in adult atopics. The palms are seldom involved. Rings and small plaques of intensely itching vesi- cles occur, which become tender and exudative once they are excoriated. Fissures over the extensor surface of the fingers are common and painful (see Photo 30). Nails: Swelling and erythema with pruritus affects the proximal nail folds. The cuti- cles may be disrupted and an acute bacterial or chronic monilia paronychia may then develop. Swelling in the proximal nail fold causes cyclical rippling of the nail plate, and disease activity in the nail matrix produces irregular coarse pitting (see Photos 30,31). Finger pads and soles: This variation is seen most often in preschool and school- aged children and may be the lone manifestation. The distal fingerpads acquire a bur- nished red appearance and the fingerprint markings are diminished or disrupted. The affected pads can be indented with light pressure and will temporarily retain the impres- sion (“ping-pong ball sign”). Symptoms are minimal and usually consist of tenderness and sensitivity. On the distal soles and toe pads, similar changes occur and are often accom- panied by itching and superficial scaling which simulates a tinea pedis. Unlike tinea pedis, however, the toe creases are usually spared. KOH prep is negative. 202 Part IV / Epidermal, Dermal, Eczematous Lesions, Atrophies Scalp: Isolated scalp involvement without other activity is common. Changes consist of prominent loose, fine, white scale that covers a base of dusky-pink erythema. Excoriations and moist open areas are the rule, often with secondary impetiginization (see Photo 32). Classic atopic dermatitis is relatively easy to diagnose. In more challenging cases, there are several ancillary physical findings that support the diagnosis. These include the following: Allergic shiners: Prominent hyperpigmentation of the lower eyelid, which imparts a fatigued look (see Photo 33). Morgan-Dennie