Grenz Zone

Grenz Zones (boundary )                      See DX Path for details of the conditions below

I always think of them as clear areas under the basement membrane but usually a Grenz Zone  represents the clear area between a florid dermal infiltrate and the basement membrane.. Consider granuloma faciale, but also B cell lymphoma and Leukaemia, Pseudolymphoma , Lepromatous leprosy and acrodermatitis chronica atrophicans.

Granuloma faciale

I admit to also thinking about amyloidosis, the collagen deposition of lichen sclerosus and the space above a dermatofibroma but technically they are not true Grenz zones.

Lichen Sclerosus