Vesiculobullous Disorders (Including Dermatitis/Eczema)
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The vesiculobullous disorders include rashes that occur in all age groups and all locations of the body. Consequently, the spectrum of disease presentations is very wide, although the keywords in this group are not as rich and varied or numerous as they are in the papulosquamous group.
“Linear vesicles” is the keyword for poison ivy, and if linear vesicles are seen in the presence of a very pruritic rash, the diagnosis of an allergic plant contact dermatitis can confidently be made. The linear vesicles are formed wherever the plant resin (a dodecacatechol chemical called urushiol) touches the skin, or wherever the resin is transported to the skin by a vector. One such vector is a pet that has the resin on its coat from touching any part of the weed, and another is clothing that has contacted the plant and which the allergic individual then touches. A third is autotransfer (by the hands) from one body site to another before the resin is removed.
The rash from a poisonous plant is a classic form of delayed hypersensitivity; the eruption does not occur immediately on touching the plant. Twelve to 24 hours later (up to 2–3 days) the eruption appears. The patient may deny contacting the plant, but the linear vesicles are so powerful a keyword that the diagnosis is secure. Three diagnoses are possible. One is poison ivy (or poison oak or poison sumac depending on the geographic locale and the plant that was touched). Although no poison oak is found east of the Rocky Mountains in the USA, most patients in the eastern USA complain of touching “poison oak”; but in truth this is oak leaf poison ivy. All these plants contain the same urushiol chemical. A second, more formal, diagnosis is allergic plant contact dermatitis; and a third is rhus dermatitis. A fourth, dermatitis venenata, means a rash from an outside source.
KeywordsLinear vesicles Linear vesicle Dermatomal vesicles Flaccid bullae Tense bullae Sausage-shaped vesicles Flexural nummular Submentum spared
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