Striae, or stretch marks, may occur if you put on weight rapidly, experience a growth spurt, or have a disorder such as Cushing's syndrome, diabetes or Ehlers-Danlos syndrome. Long-term steroid use, especially topical steroids, may also cause striae. These can weaken the skin and cause it to be more susceptible to injury. Pregnancy is a big cause of stretch marks. According to the University of Michigan Department of Dermatology, more than 50 percent of women will experience some level of stretch mark development.