Is there many cases where kids/teenagers get coronary atherosclerosis?

No. Adolescents/children are more likely to have congenital heart malformations such as a patent foremen ovale (hole between the right and left side of the heart) rather than symptomatic coronary atherosclerosis. However, early athersclerotic changes have been observed in arteries of some children. This is especially true for children at risk with obesity, hypertension, or elevated cholesterol levels.
Onset Age 7. Atherosclerosis has been known, for over 7 decades, from autopsy data, to typically begin in later childhood, age 7 y/o typical, earlier with obesity and/or diabetes, yet remains asymptomatic for decades. Arteries enlarge, not shrink. Though ivus commonly detects in teenagers, plaque rupture & clots produce narrowing, typically decades later. Thus symptomatic atherosclerosis in teenagers is rare.
Rare. There are rare genetic anomalies called progeria (see http://www. Ncbi. Nlm. Nih. Gov/pubmedhealth/pmh0002622/) and werner's syndrome (no relation to me). (see http://ghr. Nlm. Nih. Gov/condition/werner-syndrome) but both of these are very rare. Classic studies in the 50s showed 19 year olds killed in korea had early signs of arteriosclerosis - so we know that the disease begins early in life.

Related Questions

Is there any cases where teenagers get coronary atherosclerosis visible on CT scans already?

Kawasaki Disease. This is an inflammation of the arterial wall that happens rarely in young children, sometimes leading to calcification of the arteries later in life. There are also genetic abnormalities both of the arterial wall make-up as well as metabolic problems that lead to early vascular calcification.
Yes, but Unusual. Ivus commonly detects and micro-calcification can be found in early teenager years; atherosclerosis has been known, for over 7 decades, from autopsy data, to typically begin in later childhood. However, the best current ct scanners are typically incapable of detecting calcification within the base of atherosclerotic plaques until most people are early to mid 30s. The e-speed ebt machines work best.

Is there something that starts in teenagers that causes them to later get coronary atherosclerosis?

Yes. The most famous example is from autopsies of us soldiers (ages 18 and above) who died in vietnam. The aortas of many demonstrated fat-laden cells which are the first step toward atherosclerosis. No data, to my knowledge about corresponding lifestyles, but we know many were smokers.
Yes, Many... Atherosclerosis has been known, for over 7 decades, from autopsy data, to typically begin in later childhood, age 7 y/o typical, earlier with obesity and/or diabetes, yet remains asymptomatic for decades. Lipoprotein concentrations are the primary driver. Arteries enlarge, not shrink. Though ivus commonly detects in teenagers, plaque rupture & clots produce narrowing, typically decades later.

Is there many vegans that get coronary atherosclerosis?

There can be. There are multiple risk factors for atherosclerosis: hypertension, high cholesterol, diabetes, smoking, family history of heart disease or stroke, getting older, being a man. Being a vegan may help with dietary concerns that influence cholesterol levels, but it does not negate heriditary risk.
Yes, many... Atherosclerosis is an accumulation of white blood cells in artery walls, there to remove low density lipoprotein (fat carrying protein) particles. Cholesterol, about 30% of the fat molecules in all animal cell membranes, are manufactured by every animal cell, a cellular survival issue. Plants do not make cholesterol. Cholesterol is promoted as a way to estimate lipoproteins; but was never correct.