Not a stretch: Variant near the dermal gene elastin is associated with stretch marks. M. E. Mullins, N. Eriksson, A. K. Kiefer, J. Y. Tung 23andMe, Inc., Mountain View, CA.

   Striae distensae, or stretch marks, are a common skin condition that appear as red or white lines on the skin. Though stretch marks are only harmful in extreme cases, even mild stretch marks can cause distress. The portions of cosmetic/pharmaceuticals and maternity-care industries that offer stretch mark prevention and treatment products are estimated to be worth $5-10 billion annually.
   Despite the range of products claiming to prevent and treat stretch marks, the causes of stretch marks are not well understood. Skin distension, such as that which occurs during pregnancy or puberty; prolonged exposure to cortisols, such as in individuals with Cushing syndrome; and genetics have all been implicated. A small number of monogenic diseases, including Marfan syndrome and Ehlers-Danlos syndrome, count stretch marks amongst their characteristics. Both these syndromes are caused by mutations in genes that encode dermal proteins. To date, no genes are known to be associated with the stretch marks that afflict the general population.
   We conducted a genome-wide association analysis of stretch marks using approximately 7 million SNPs imputed from about 1 million SNPs genotyped. Phenotypic data was self-reported by over 30,000 23andMe customers who responded to the following question on the 23andMe website: Do you have stretch marks on your hips, thighs, or backs of your arms? Yes/No/Im not sure. We found a genome-wide significant association (p-value 1.28E-12) with rs6946106, which is upstream of elastin (ELN). Defects in ELN are known to affect the integrity of the skin and cause aortic defects.
   We also detected a second association (p-value 3.86E-8) with rs35318931, a missense mutation in sushi-repeat containing protein, X-linked (SRPX).
   These results show a genetic component to stretch marks: defects in ELN may influence skin remodeling after stress. Many stretch mark sufferers spend hundreds of dollars on stretch mark treatments that offer minimal results. A better understanding of the etiology of stretch marks could help develop more targeted and effective treatment or prevention strategies.