WSVN -- A few years ago Sam Jonas noticed something strange.
Sam Jonas: "One day I just noticed that something was going on with my nails on my hand and didn't know what it was."
It turned out to be psoriasis, an auto-immune disorder that causes red, flaky skin. Then two years later the unexpected happened.
Sam Jonas: "My friend and I were going to the beach with our kids and on the way to the beach I started feeling very, very nauseaus."
Sam had a heart attack and was rushed to the hospital where doctors treated a blockage in his heart.
Sam Jonas: "When they told me I was having a heart attack I just didn't even believe them. It never occured to me."
But what really shocked Sam, his doctor told him the psoriasis may have led to his heart attack.
Dr. David Ancona: "We are finding that there are links between diseases, particularly these autoimmune diseases, such as psoriasis and heart disease."
Dr. David Ancona at Memorial Hospital West says it's called shadow diseases.
Dr. David Ancona: "Shadow diseases are diseases that seem to go hand in hand, one kind of follows the other."
Doctors say they don't know why exactly, but one illness seems to lead to another condition that's unrelated.
Other links have been found too like asthma and depression, high blood pressure and diabetes, and studies show if you suffer from migraines once a week you are four times more likely to have a stroke!
In sam's case his psoriasis was causing problems with his heart.
Dr. David Ancona: "It not only affects the skin but then starts affecting the internal body as well, the heart, your joints."
Dr. Ancona says if you have psoriasis or any other illness, it's important to know if there is a shadow disease, learn the risk factors and get regular checkups.
Dr. David Ancona: "As a cardiologist if I find psoriasis I'm definitely on the hunt for coronary artery disease and will treat it more aggressively."
Looking back, Sam wishes he had known about his shadow disease.
Sam Jonas: "Had I known that before I probably would have been a little bit more proactive about getting a checkup."
Richard Lemus: "Doctors say knowing about common shadow diseases can promote early diagnosis and treatment."