Pachyonychia congenita Jadassohn-Lewandowsky: a disorder of keratinization.

A 15-month-old boy with pachyonychia congenita is described. The patient also had follicular keratosis, leukokeratosis of the tongue, and blisters on the soles. Histopathological examination of the follicular keratosis showed hyperkeratosis and acanthosis. Horny plugs were located in sweat pores. By electron microscopy abnormal keratinization was demonstrated.