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.