Morphology of atopic eczema

The routine examination of skin biopsy specimens embedded in paraffin and strained with hematoxylin‐eosin has failed to allow differentiation of atopic eczema from other types of eczematous dermatitis. The use of 1‐μm plastic‐embedded sections permits the recognition of in filtrating cell types and blood vessel alterations, thus allowing a refined method to examine cutaneous lesions and permit better definition of cutaneous structures than can be achieved in routinely‐processed specimens. Acute vesicular lesions exhibited marked epidermal intercellular edema (spongiosis) and a dermal inflammatory infiltrate of lymphocytes, and activated lymphocytes with normal numbers of mast cells that exhibited various degrees of hypogranulation. Only rare eosinophils, neutrophils, and basophils were noted. Venular alterations included endothelial cell hypertrophy without necrosis. In lichenified plaques there was epidermal hyperplasia with a dermal inflammatory infiltrate that included increased numbers of fully granulated mast cells and increased numbers of lymphocytes and monocyte‐macrophages. Alterations of venules included marked endothelial cell hypertrophy and basement membrane thickening. Cutaneous nerves exhibited demyelination and fibrosis. Also, increased numbers of Langerhans' cells have been noted in the epidermis of chronic lesions. Despite the absence of eosinophils, major basic protein has been demonstrated in the dermis by direct immunofluorescence techniques. Studies of lymphocyte subsets have shown increased numbers of CD4 + T lymphocytes.