Papular lesions and thickened nails on the feet: A "Don't Walk" sign?

Your patient is a 14-year-old boy who complains of bilateral foot pain of several weeks' duration. Sometimes, he tells you, the pain is so bad that he cannot bear weight and has to crawl from place to place. As you talk with him, you note that all 10 fingernails are abnormally thick and raised.

His nails have looked this way for as long as he can remember, he tells you. Furthermore, his father's nails look the same way, and he complains of foot pain from time to time, too.

This rare autosomal dominant disorder was first described extensively by Jadassohn and Lewandowsky in 1906.¹ Mutations in the genes that encode keratins 6, 16, and 17 result in structural disruption of keratin in the nail, hair follicle, tongue, palm, and sole.²

Approximately 250 cases have been reported in the literature.² Pachyonychia congenita affects both sexes equally, with a higher prevalence found in people of Jewish and Yugoslavian descent.¹

What are the signs and symptoms?

Several classifications of pachyonychia congenita have been proposed, based on the most common clinical findings of dystrophic nails, palmollantar keratosis, follicular hyperkeratosis, and oral leukokeratosis.³ Agreement on any one classification is, however, lacking.^1,2,4

Affected people develop yellow-brown, tented, symmetrical thickening of the distal two thirds of all fingernails and toenails. The nail plate is elevated by subungal keratinous material; the elevated nails may be painful and thus interfere with fine motor activity. Although changes in the nails are usually seen in infancy, onset during adolescent years-or beyond-occurs occasionally and is known as pachyonychia congenita tarda.

Keratotic papules and plaques form on the palms and soles. Plantar calluses, with painful blisters and fissures, may form at pressure points. Aggravating factors include warm weather, trauma, and ill-fitting shoes.⁵

Oral leukokeratosis is characterized by white, opaque, asymptomatic thickening of the buccal mucosa and tongue (see the photograph, upper right). It is generally asymptomatic and is not associated with malignant transformation.

Other reported associated findings include palmoplantar hyperhydrosis, natal teeth, angular cheilosis, hair abnormalities (kinky hair, thick hair, or alopecia), hoarseness, cataracts, blindness, mental retardation, and conductive deafness.^2,6