Scientists still don’t know exactly what causes psoriasis, but the general consensus is that the most likely cause of this chronic autoimmune disorder is a combination of specific immune-related gene mutations (changes) and environmental triggers. But just how much does having a family member with psoriasis increase one’s risk of developing the condition? Science offers a lot of information and theories, but some questions remain.

When a Parent Has Psoriasis

While psoriasis can occur in people who don’t have a known family history of the condition, doctors believe having a family member with psoriasis increases the risk.

According to the National Psoriasis Foundation, you have about a 10 percent chance of getting psoriasis if one of your parents has it. And if both of your parents have it, the risk increases to 50 percent. It’s estimated that one third of people with psoriasis (that’s 125 million worldwide, equal to 2 to 3 percent of the population—including more than 8 million in the U.S. alone) have a relative who has it, too.