Source:
http://www.nature.com/jid/journal/v1...d2015197a.html
Definition of terms
What is Hypertrophic Scarring or HTS? Hypertrophic scarring (HTS) is a fibroproliferative response to cutaneous injury that occurs in over 70% of burns requiring hospital admission, resulting in scar raised above the skin level but within the boundaries of the original wound. It is not known whether race has implications on HTS, until this study. Given the apparent association between skin pigmentation and HTS formation, genes involved in skin pigmentation may contribute to HTS. Melanocortin signaling is known to be a chief determinant of pigmentation, as binding of α-melanocyte-stimulating hormone (α-MSH) to the G-protein-coupled melanocortin 1 receptor (MC1R) causes melanocytes to produce dark eumelanin in favor of light pheomelanin. The MC1R gene is highly polymorphic with over 80 known variant alleles, many of which alter function. Some of these loss-of-function variants are associated with red hair and fair skin and increased risk of skin cancers, especially melanoma. However, several MC1R variants are also known to be common among dark-skinned races that seem predisposed to HTS; in one study, the loss-of-function R163Q single–nucleotide polymorphism (SNP) had an allele frequency of 70% among East/Southeast Asians and 100% in Native Americans.
Results
In unadjusted analysis, the prevalence of severe HTS varied significantly according to race (P<0.0001), with a higher prevalence among Asians (prevalence ratio (PR)=1.45; 95% CI=1.05–2.00), Blacks (PR=1.78; 95% CI=1.34–2.36), and Native Americans (PR=1.98; 95% CI=1.52–2.57) compared with Whites. In a multivariate model adjusting for several known risk factors for HTS, Asian, Black, and Native American race were each independently associated with risk of severe HTS. Burn size and number of operations were also independently associated with HTS severity, corroborating previous reports.
When the multivariate model was expanded to include genotype data for five MC1R SNPs, the R163Q variant (PRadj=1.35; 95% CI=1.14–1.53) was independently associated with severe HTS after accounting for multiple testing. This significant association persisted when the multivariate analysis was limited to White subjects only, indicating that the association was not driven by the Asian and Native American subjects, who had a higher prevalence of both severe HTS and R163Q. In a model including an interaction between R163Q genotype and race, there was no evidence of effect modification by race (P=0.27), although this analysis was likely under-powered due to small numbers in the non-white race categories.
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