A. Tatian1, D. Slape1, J. Frew1,2,3
Introduction: Pachyonychia Congenita (PC) describes a group of genodermatoses manifesting in thickened nails, palmoplantar keratoderma and increased risk of cutaneous infections. Variable features including natal teeth and oral leukokeratosis. Delayed onset PC has also been described, termed Pachyonychia Congenita Tarda,1 with onset ranging from late childhood to middle age, and responsible genetic polymorphisms have been identified. It is unclear whether there is overlap between any identified genetic polymorphisms in PC and PC Tarda which may indicate an as-yet-unidentified epigenetic mechanism which may be responsible for the delayed onset of symptoms.
Methods: We aimed to conduct a systematic review of all reported cases of Pachyonychia Congenita Tarda in the published literature. This review was registered with PROSPERO. PubMed, EMBASE and PsychINFO databases were examined for case reports of PC Tarda with no search restrictions on date or language. Identified cases were screened independently by two authors based on pre-determined criteria. Any disagreements were mediated by referral to a third author for mediation. Data was extracted and collated. All reported genetic polymorphisms were compared to multiple genetic databases (dbSNP, HGVD, OMIM) for correlation with known polymorphisms in PC.
Results: 17 articles reporting 16 pedigrees were identified. Identified genetic polymorphisms occurred in similar domains as reported variants in PC. No common polymorphisms were identified between PC and PC Tarda. Epigenetic mechanisms contributing to the delayed phenotype in PC Tarda cannot be excluded.
1. Paller AS, Moore JA, Scher R. Pachyonychia congenita tarda. A late-onset form of pachyonychia congenita. Arch Dermatol 1991; 127:701–3.