Isotretinoin (Accutane) is a vitamin A–like drug used to treat severe acne. It is a pill that is taken by mouth and is usually given to people who do not respond to treatment applied directly to the skin (topical). Isotretinoin may cause side effects, including birth defects, liver problems, hair loss, and increases in fatty substances in the blood (triglycerides). Researchers do not know why or how isotretinoin increases triglyceride levels. They think that persons who have a family or genetic tendency to develop very high levels of triglycerides and cholesterol are the ones who develop this side effect. Thus, if persons develop high triglyceride levels while taking isotretinoin, it could indicate that they have an inherited problem with fatty substances in the blood (familial combined hyperlipidemia). This inherited disorder is usually diagnosed in early adulthood. People with the disorder have high levels of triglycerides and cholesterol (fatty substances) and can develop diabetes, high blood pressure, and obesity. They have increased risks for having a heart attack at a young age.