Mucha-Habermann disease (PLEVA)

Early

Wedge-shaped, superficial and, sometimes, deep perivascular and interstitial infiltrate of lymphocytes
Lymphocytes and vacuolar alteration obscuring the dermoepidermal junction
Individual necrotic keratinocytes scattered within the epidermis, especially the lower half; few or many
Slight spongiosis and ballooning
Slight pallor in the upper part of the epidermis
Cornified layer basket-woven in configuration

Fully developed
All of the features of early lesions plus:

Wedge-shaped infiltrate of lymphocytes usually deep as well as superficial
Lichenoid array of lymphocytes in section from some specimens
Vacuolar alteration marked sometimes with separation along the dermoepidermal junction and, eventually, subepidermal vesiculation
Numerous individual necrotic keratinocytes within the epidermis; confluent necrosis sometimes, also in wedge shape
Spongiosis and marked ballooning resulting sometimes in intraepidermal vesiculation accompanied by reticular alteration; rupture of an intraepidermal vesicle also resulting in a subepidermal vesicle
Marked pallor at times in the upper part of the epidermis
Mounds of parakeratosis and/or scale-crusts usually housing neutrophils

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