[The nail in vascular pathology].

The nail is part of the ungual unit; it is affected indirectly and late in vascular disease. The authors recall the anatomy and the blood supply of the ungual unit and describe the alterations in terms of the level of the lesion. They describe the changes seen in systemic diseases such as the collagen disease, in vascular disease, venous, arterial and lymphatic disease and in vascular acrosyndromes. These alterations are often a result of several diseases, but may, nevertheless, help orient the diagnosis.