What causes plaque in arteries that could form a clot. Can smoking alone do it or needs to be multiple reasons and usually what age?

Multiple causes! Genetic factor,high cholesterol in the form of oxidized LDL, triglyceridemia & inflammatory process. Cigarette smoking is considered the most important risk factor for coronary heart disease.Tobacco smoke contains more than 4000 chemicals of which more than 50 have been identified as carcinogens.These chemicals are extremely damaging to the heart.Common above 50, any age depending on risk facto.
Plaque. There are several risk factors for Peripheral Arterial Disease: 1. Smoking; 2. Diabetes; 3. High Blood Pressure; 4. High Cholesterol 5. Family History; 6. Being over the age of 50. Also being overweight can put you at risk. You must control your risk factors and see a Vascular Surgeon if you start to develop signs and symptoms.