Psoriasis: Histology

 Histology (Fig. 5.2)

The main changes are the following.

1  Parakeratosis (nuclei retained in the horny layer).

2 Irregular thickening of the epidermis, but thin-ning over dermal papillae is apparent clinically when bleeding is caused by scratching and the removal of scales (Auspitz’s sign).

3 Polymorphonuclear leucocyte microabscesses (des-cribed originally by Munro).

4 Dilated and tortuous capillary loops in the dermalpapillae.

5 T-lymphocyte infiltrate in upper dermis.

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