Basal layer damage

Basal Layer Damage

Marked basal layer damage is a feature of Erythema multiforme and its variants Stevens Johnson syndrome and Toxic epidermal necrolysis. We call this interface reaction pattern. It may also be seen to a lessor degree in lupus erythematosus and lichen planus and in the PLEVA variant of Pityriasis lichenoides. There are many fewer lymphocytes at the DEJ in interface as against lichenoid reactions.
Older terms for these changes were liquifactive degeneration and hydropic degeneration.

Lichenoid reaction pattern may overlap here but usually gives less vacuolar changes at the DEJ than interface damage  and there is a denser lymphocytic infiltrate hugging the DEJ.