Severe nail dystrophy is a recently described acquired nail disorder. The nails are variably involved and may show thinning, thickening, pitting, ridging, koilonychia, opalescence, and loss of luster. Not uncommonly, some nails are completely spared. Although most of the cases reported were among children, and nail changes showed gradual resolution, in a few cases the disorder is seen in adulthood. We recently investigated a pedigree extending through five generations in which twenty-one of the thirty-seven members were variably afflicted with the dystrophic nail changes. To our knowledge, the familial pattern, inherited as an autosomal dominant trait, has never been previously reported. We propose the term "familial severe twenty-nail dystrophy" for the disorder in this family.