Presented at the 2013 AAPM Annual Meeting « Back

Exploring Pain in Pachyonychia Congenita

Tim J. Wallis, MA BM, timothywallis@hotmail.com¹, Chris D. Poole, PhD², Barbara Hoggart, MBBS FFPMRCA³, (1) University Hospital Southampton, Bournmouth, Dorset, England, (2) Cardiff University, Cardiff, Wales, United Kingdom, (3) Heart of England NHS Trust, Solihull, West Midlands, United Kingdom

Introduction: Pachyonychia Congenita(PC) is a rare skin disorder caused by an autosomal dominant mutation in one of four keratin genes K6a, K6b, K16, & K17 [1]. While pain is a significant symptom, severity and type are poorly characterised. 35 genotyped US Caucasian patients with PC were examined & completed Brief Pain Inventory (BPI), painDETECT (PD)[2] & EQ-5D index (QoL scored with US tariff [3]). General linear modelling was used to explore correlation between QoL & clinical features (SPSSv18). Mean age 46.7 years (SD 15.9), 51% male. The K16(40%) & K6a (31%) subtypes predominated over K17 (20%) & K6b (9%). Significant pain was present, indicated by mean BPI 'average pain' of 4.7 (95% CI 4.1-5.3), and QoL impairment, indicated by mean EQ-5D index of 0.680 (0.610 to 0.741). Neuropathic pain was evident in 63% of patients, the remainder being nociceptive. BPI 'average pain' was most significantly related to QoL (p=0.001) followed by PD score (p=0.006). In a model adjusting for pain (R2=0.445), the K17 & K6a subtypes exhibited significantly worse QoL (0.604 & 0.637 respectively) than did the K16 & K6b subtypes (0.729[p=0.089] & 0.867[p=0.015] respectively). Pain is a primary symptom in PC and a major determinant of QoL. The health status observed in this sample is such that the average US citizen would forfeit one-third of remaining lifespan to avoid. Neuropathic pain of this severity warrants effective treatment. References: 1) McLean, W.H. et al. Keratin 16 and keratin 17 mutations cause pachyonychia congenita. Nature Genet. 1995; 9; 273-278. 2) Freynhagen R, Baron R, Gockel U, Tölle TR. PainDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain. Curr Med Res Opin. 2006 Oct; 22(10); 1911-20. 3) Shaw, JW; Johnson, JA; Coons, SJ. US valuation of the EQ-5D health states - Development and testing of the D1 valuation model. Medical Care 2004; 43(3):203-220.

Funding: Grant from Pachyonychia Congenita Project

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