Pachyonychia congenita is a rare inherited disorder of keratinization that primarily affects the nails and skin. Affected people develop thickened skin on the soles and palms, white patches on the tongue and mouth, and bumps around the elbow and knees. 

What is the cause of pachyonychia congenita?

The disorder is caused by a genetic mutation but features vary depending on the affected gene. Five keratin specific genes are involved: K6a, K6b, K6c, K16, and K17. These genes provide instructions for the synthesis of keratin; a protein found in the skin, hair and nails. The frequent pathogenic variant is in K6a.

 

Pachyonychia congenita is inherited in an autosomal dominant manner. It is found in ethnic groups and occurence is equal in both sexes.

What are the clinical features of pachyonychia congenita?

Clinical features vary based on the involved keratin gene and specific genetic mutation but it is usually characterized by:

  • Calloused palms and soles with plantar pain in most of the patients. Sometimes underlying blisters are present 
  • Thickened nails often with brown discoloration. 
  • Certain types of sebaceous gland cysts, steatocystoma and pilosebaceous, are found in PC patients.
  • White patches affecting the tongue and inside of the mouth. 

Diagnosis

Diagnosis is based on the presence of clinical signs and appearance. There is a clinical diagnostic criteria that includes the triad of the commonest features of toenail thickening, plantar keratoderma and plantar pain of pachyonychia congenita (PC) In addition, detection of a mutation in only one of the aforementioned genes confirms PC diagnosis. 

What is the treatment of pachyonychia congenita?

Limiting certain physical activity like walking, maintaining ideal body weight, and wearing ventilated shoes with moisture-wicking socks. Regular trimming of nails and calluses when necessary, and if needed, appropriate treatment of infections. Topical therapy to remove hyperkeratosis includes emollients and retinoids.

Pachyonychia congenita is an extremely rare disease that does affect the lifespan of the affected person, however it can negatively impact the quality of life. The pain and appearance of this condition can interfere with day-to-day activities and social life. 

Written by: Naif Alalshaikh, Medical student.

References

  1. “Pachyonychia Congenita.” Pachyonychia Congenita | DermNet NZ, https://dermnetnz.org/topics/pachyonychia-congenita
  2. “Pachyonychia Congenita.” Genetic and Rare Diseases Information Center, U.S. Department of Health and Human Services, https://rarediseases.info.nih.gov/diseases/10753/pachyonychia-congenita. 
  3.  PMC, Europe. Europe PMC, https://europepmc.org/article/nbk/nbk1280#free-full-text