Keloid disease is a fibroproliferative dermal tumor with an unknown etiology that occurs after a skin injury in genetically susceptible individuals. Increased familial aggregation, a higher prevalence in certain races, parallelism in identical twins, and alteration in gene expression all favor a remarkable genetic contribution to keloid pathology. It seems that the environment triggers the disease in genetically susceptible individuals. Several genes have been implicated in the etiology of keloid disease, but no single gene mutation has thus far been found to be responsible. Therefore, a combination of methods such as association, gene-gene interaction, epigenetics, linkage, gene expression, and protein analysis should be applied to determine keloid etiology.
Keloid is a complex condition with environmental and genetic risk-contributing factors. Two candidate genes, TGFβ1 and SMAD4, located in the same signaling pathway are highly expressed in the keloid fibroblast cells. In a case-control design, TGFβ1 haplotypes showed association with the risk of keloid in the present study. The CC haplotype, composed of both c.29C>T and -509T>C variants, was observed more frequently among cases (Corrected p = 0.037, OR = 2.07, 95 % CI = 0.87-4.93), showing a 4.5-fold increased risk for keloid. The AG genotype of the SMAD4 c.5131A>G variant showed a trend of significance (p = 0.0573, OR = 1.75, 95 % CI = 0.99-3.13). Taken together, either of these variants is most probably causative at the expression level or is in linkage disequilibrium with other causative variants in a complex pattern together with the environmental factors that contribute to the condition. To the best of our knowledge, there is only one documented report on a relationship between TGFβ1 and keloid with no association within the Caucasian population, while there have not been any reports for SMAD4. Therefore, the present study is likely the first research showing a significant association between TGFβ1 variants and keloids in the Malay population.