Pachyonychia congenita tarda.

Pachyonychia congenita is a distinct hereditary disorder of keratinization, in which dystrophy of all nails is associated with palmoplantar keratoderma and other hyperkeratoses. Recently a late-onset type has been reported. We report a second family with late-onset pachyonychia congenita, showing a remarkable clinical heterogeneity. Furthermore, one patient demonstrated a number of associated hyperkeratoses not previously recognized. Acitretin proved useful in the treatment of this late-onset form of pachyonychia congenita.