Apport de l'histopathologie dans le diagnostic d'une onychopathie

The clinical feature of inflammatory nail diseases, without skin symptoms is misleading. Five situations very frequent in daily practice have been selected. Two classical clinical situations are analyzed : (i) onychomycosis with special reference to a new microanatomic structure, the nail isthmus as the first step of fungal invasion in the nail plate, and (ii) trachyonychia. Three new syndromes have discussed : vegetant and subcorneal dermatosis, including vegetant granuloma pyogenic; hyponychial dermatosis; nail degloving syndrome. In the field of longitudinal melanonychia, a multi step, as questions-answers, differential diagnosis approach is proposed. This approach is helpful for distinguishing simple melanocyte activation from lentigo, and junctional nevi from malignant melanoma. Two new localized (monodactylic) longitudinal syndromes have discussed in a detailed description. Pachy-xanthonychia longitudinal syndrome including onychomatricoma and onychogenic bowen disease and localized longitudinal erythronychia.