USMLE – Eczema
The terms ‘eczema’ and ‘dermatitis’ are synonymous. They refer to distinctive reaction patterns in the skin, which can be either acute or chronic and are due to a number of causes.
In the acute stage edema of the epidermis (spongiosis) progresses to the formation of intraepidermal vesicles, which may enlarge and rupture. In the chronic stage there is less edema and vesiculation but more thickening of the epidermis (acanthosis); this is accompanied by a variable degree of vasodilatation and T-helper lymphocytic infiltration in the upper dermis.
There are two groups of eczemas: exogenous and endogenous. While overlap between the two groups is common, distinction between them is critical for treatment because avoidance of incriminating contactants takes precedence over other measures in the management of exogenous eczema.
The clinical signs are similar in all types of eczema but vary according to the duration of the rash.