By Gary M. White, MD
Pachyonychia congenita (PC) is an autosomal dominant disorder in which all fingers and toenails are greatly thickened, hard and curved transversely. It is caused by mutations in one of five keratin genes; KRT6A, KRT6B, KRT6C, KRT16 or KRT17. To date, no genetically confirmed cases have an autosomal recessive inheritance pattern. Two phenotypes have been described. Type 1 phenotype (nail dystrophy, palmoplantar keratoderma, and oral lesions), and type 2 phenotype (nail dystrophy, pilosebaceous cysts following puberty, natal teeth).
The nails are thickened with significant curvature. There is often a palmoplantar keratoderma. Keratotic papules may occur on the knees and elsewhere.
In one study [JAMA Dermatol. 2014 Feb;150(2):146-53], nail thickening and plantar keratoderma occurred before school age in more than three-quarters of children. For adolescents, the most psychologically disturbing features were the visible nail changes and the painful plantar thickenings.
Many adults use canes or crutches to walk. Ultrasound has shown occult plantar blisters in the soles of patients causing great pain. 45% of patients have no family history. Over 100 different mutations have been identified.
See also Pachyonychia Congenita Project
There is no specific gene therapy or treatment. Most important is focussing on reducing the pain of the keratoderma. "Not too thick and not too thin" is the motto for the keratoderma. Weekly or more frequent mechanical trimming is the most reliable therapy.
The nails may be filed down as well. Keratolytics may be used on the palmoplantar keratoderma. Complete removal of painful nails can be beneficial and patient reported outcomes are overall favorable [JAAD 2017;76;990].
The use of sirolimus improved the quality of life of three patients [J Dermatol Sci. 2009 Nov;56(2):82-8]. (Sirolimus inhibits keratinocyte proliferation by selectively blocking expression of keratin K6A.)
Keratotic papules on the knees.
Keratotic papules. JAAD December 2008;Volume 59, Issue 6, Pages 1050–1063
Oral leukokeratoses. Pachyonychia Congenita Project
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