Atopic dermatitis (AD) has a prevalence of 1%-3% in adults. Adult-onset AD has only been defined recently, and lack of familiarity with this condition and confusion regarding the appropriate terminology persist. AD may first appear in childhood or de novo in adults and is characterized by pronounced clinical heterogeneity. The disease often deviates from the classic pattern of flexural dermatitis, and there are forms of presentation that are specific to adults, such as head-and-neck dermatitis, chronic eczema of the hands, multiple areas of lichenification, or prurigo lesions. Although diagnosis is clinical, adult-onset AD frequently does not fit the traditional diagnostic criteria for the disease, which were developed for children. Thus, AD is often a diagnosis of exclusion, especially in de novo cases. Additional diagnostic tests, such as the patch test, prick test, skin biopsy, or blood test, are usually necessary to rule out other diseases or other types of eczema appearing concomitantly with AD. This article presents an update of the different forms of clinical presentation for AD in adults along with a proposed diagnostic approach, as new treatments will appear in the near future and many patients will not be able to benefit from them unless they are properly diagnosed.

Atopic Dermatitis in Adults: A Diagnostic Challenge.

Atopic dermatitis beginning in adult life is not mentioned in the medical literature. In a review of 2604 patients attending a contact dermatitis clinic, 243 patients (9%) were diagnosed with atopic dermatitis which began for the first time at 20 years of age or older with no contact factors present. This compares with 213 patients (8%) who had atopic dermatitis and contact dermatitis. Patients with purely atopic dermatitis had negative patch testing to relevant allergens and the diagnosis was based on a personal or family history of atopy as well as elevated IgE levels and multiple positive skin prick tests. A broad range of age of onset was found, as well as a female preponderance. The commonest sites of dermatitis were generalized involvement, dermatitis of the hands or eczema involving the face.

Adult-onset atopic dermatitis.

Eczema, Lichenification, Prurigo and Erythroderma

Demographic distribution of the population is progressively changing with the proportion of elderly persons increasing in most societies. This entails that there is a need to evaluate the impact of common diseases, such as asthma and other allergic conditions, in this age segment. Frailty, comorbidities and polymedication are some of the factors that condition management in geriatric patients. The objective of this review is to highlight the characteristics of allergic diseases in older age groups, from the influence of immunosenescence, to particular clinical implications and management issues, such as drug interactions or age-related side effects.

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Allergic diseases in the elderly.

Allergic skin disorders in the elderly may arise from contact with or ingestion of offending allergens. Itching associated with skin allergy must be distinguished from other causes of itching in the elderly such as xerosis, itching due to systemic disease and bullous disease. Although elderly people have somewhat decreased cell-mediated immunity and may be harder to sensitise under experimental conditions, they have had many years to acquire allergic responses, and therefore develop contact dermatitis frequently. Patch testing is a valuable tool to diagnose contact allergy and should be used often in the elderly, particularly in patients at high risk of contact dermatitis, such as those with chronic lower extremity dermatitis or ulcers due to venous stasis. When prescribing topical medications to high risk patients, a knowledge of the common sensitisers is important. In addition to allergy to medicaments and dressings used to treat stasis ulcers, contact allergy to dental prostheses and medications used to treat ocular disease are common in the elderly as a result of increased usage and exposure. Rash caused by ingested allergens is much more commonly due to medications than to food in the elderly. Allergic noneczematous dermatoses in the elderly are commonly drug-induced. Urticarial skin reactions are often associated with the administration of antibacterials, nonsteroidal anti-inflammatory drugs (NSAIDs), antidepressants or opioids. Morbilliform rashes are a common sign of systemic reaction to anticonvulsants, gold, allopurinol or diuretics. Phototoxic reactions may be associated with the administration of tetracyclines, diuretics, NSAIDs and antihyperglycaemic agents. Patient-specific variables such as HLA type and concomitant medication may affect the likelihood of an allergic response to medication. Many elderly patients take multiple medications, which can make diagnosis of drug allergy difficult because diagnosis is most commonly accomplished by observing clinical response once the medication is withdrawn. In the case of lichenoid cutaneous reactions, clinical improvement may take several months after withdrawal of the offending drug. Laboratory tests to detect drug-induced allergic skin disorders may be available in the future.

Diagnosis and treatment of allergic skin disorders in the elderly.

Patients with intractable eczema are often referred for patch testing to exclude contact dermatitis. If this is excluded, then a diagnosis of endogenous eczema is made. At our clinic, we find a sizeable proportion of these patients do not fit any of the known patterns of endogenous eczema. These patients are given the diagnosis of unclassified endogenous eczema and make up 8% of the patients seen at our Occupational and Contact Dermatitis Clinic. There is little information available on this group of patients, with no mention of this problem in the recent dermatological literature. Since March 1996, we have further investigated these patients, to develop some understanding of this category. 12 of 34 patients reviewed over this period had an elevated IgE level above 100 IU/ ml. Thus, despite no past history or family history of eczema, asthma or hayfever, at least 1/3 of these patients are probably suffering from atypical, late onset atopic dermatitis. Patients were later contacted by telephone (average 2 years) to assess the natural history of this condition. In 20 of the 31 patients contacted, their eczema had either improved or resolved. We think that this important category of eczema needs to be recognized and further investigated.

S Freeman

Papers

Unclassified endogenous eczema.