Acral Eczematous Diseases
Several eczematous diseases preferentially involve the hands and feet. For this reason one should not use the term “hand eczema” or “foot eczema” as a diagnostic term. One must specifically attempt to identify which process is responsible: atopic dermatitis, dyshidrotic eczema, scabies, contact dermatitis, or secondary eczematization of a noneczematous disease. Guidelines for the recognition of these separate processes are covered .
Genital and Perigenital Eczematous Diseases
The situation for eczematous diseases of the groin is analogous to that of acral dermatitis. It is not sufficient simply to make a diagnosis of “diaper dermatitis” or “pruritus ani.” One must attempt to recognize specifically which of several eczematous conditions is responsible for the observed changes. Guidelines for doing so are contained .
Nummular Eczema. The adjective “nummular” is derived from the Latin word for coin. Thus nummular lesions are characterized by sharp margination and by coin-like roundness and coin-like size. This is a very common morphology; in fact, nummular lesions can be found in all ten disease groups. The term is most commonly used for small round eczematous lesions, however. Nummular patterns are most often seen in xerotic eczema and in atopic dermatitis. Occasionally, some of the lesions scent in autoeczematization are also nummular. Some clinicians use the term “nummular eczema” as if it were the name of a single disease, but in most instances nummular eczematous lesions can be more specifically assigned as variations of atopic dermatitis, xerotic eczema, or autoeczematization.
Autoeczematization (Autosensitization, “Id” Reaction)
There is a marked tendency for severe eczematous disease, regardless of type, to spread spontaneously outside of its original distribution pattern. The reason for this spread is unknown, but it is widely believed to occur as the result of an immunologic reaction mounted against antigens located at the original site of involvement. The putative antigens include proteins of external origin (bacteria and fungi) and proteins of internal origin (keratin and collagen) that have been modified some way by the original disease process.
Conceptually, auto eczematization can be considered as “metastatic” spread of an eczematous disease. Local, contiguous extension could then be viewed as “lymphatic metastases,” and distant, noncontiguous lesions could be viewed as “hematogenous metastases.”
Autoeczematization is most often seen in association with diaper dermatitis, stasis dermatitis, external otitis, hand eczema, and foot eczema. Historically, autoeczematization was first recognized in individuals with tinea pedis who subsequently developed vesicular and eczematous disease of the hands. This process was called the “dermatophytid reaction,” and from this the term “id” reaction has been derived.
The lesions of autoeczematization are frequently vesicular when they occur on the hands, but they are more typically eczematous when they occur on the face, arms, legs, and trunk. In these latter locations the lesions of auto eczematization often assume a nummular pattern. The ultimate form of auto eczematization is that of exfoliative erythrodermatitis wherein nearly the entire skin surface becomes involved with eczematous disease.
Patients with autoeczematization usually do not respond well to simple measures such as soaks and topical steroids. In most instances a burst of systemically administered steroids will be required. When systemically administered steroids are used, the auto eczematous lesions respond promptly, but the underlying, original disease clears more slowly. Failure to continue treatment until the original lesions are completely healed is usually followed by rapid recrudescence of the entire process.
Tags:contact dermatitis, dyshidrotic eczema, eczema, Eczematous Diseases, hand eczema, Lesions nummular eczema
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