Pachyonychia Congenita type 2 (PC2)

Pachyonychia congenita (PC) is characterized by thickened and friable finger and toe nails often apparent at birth or soon after. There are painful plaques of callus-like hyperkeratosis (keratoderma) on palms and soles with underlying blisters, hyperhidrosis and some individuals may have spiny follicular hyperkeratosis elsewhere on the body. Patients who also have natal teeth, alopecia and epidermoid cysts were previously described as having PC type 2. Patients with oral leukoplakia (a finding absent in PC type 2) were previously described as having PC type 1. However, recent genotype/phenotype correlation reports favor the more general nomenclature of pachyonychia congenita (PC) due to high phenotypic overlap between the subtypes. Heterozygous mutations in five keratin genes have been associated with PC: KRT16, KRT6A, KRT17, KRT6B, and KRT6C. Patients with KRT6C mutations typically have callus-like palmoplantar keratoderma with little or no nail dystrophy. In steatocystoma multiplex, multiple round or oval sebaceous (epidermoid) cysts develop, widely distributed over the back, anterior trunk, arms, scrotum, and thighs. Thickened nail plates, focal palmoplantar keratoderma and natal teeth are variable features.

Tests Available

Forms and Documents

Test Info Sheet Test Requisition

Test Details

KRT17, KRT6B
  • Confirmation of clinical diagnosis
  • Prenatal diagnosis
  • Capillary Sequencing

Ordering

2092
6 weeks
2-5 mL Blood - Lavender Top Tube
Oral Rinse (30-40 mL) | Buccal Swabs

Billing

81479x1
Yes
Yes
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References

  1. Van Steensel et al. Clouston syndrome can mimic pachyonychia congenita. J Invest Dermatol 121:1035-1038, 2003
  2. Smith et al. Missense mutations in keratin 17 cause either pachyonychia congenita type 2 or a phenotype resembling steatocystoma multipolex. J Invest Dermatol 1108:220-223, 1997
  3. Terrinoni et al. Novel and recurrent mutations in the genes encoding keratins K6a, K16 and K17 in 13 cases of pachyonychia congenita. J Invest Dermatol 117:1391-1396, 2001