a lot of them you don't "catch".
cancer is caused when "bad" or malignant cells, grow out of control, and take over the good ones. in some types of cancer, it causes tumors. some can be removed with surgery, some require chemo. however, leukemia is a type of cancer that affects the blood.
leukemia IS, more common in children. it happens when the "bad" blood cells take over the "good" blood cells, and the immune system begins to attack itself rather than attack the "bad"cells. thats called (acute lymphonic leukemia) or ALL. (i dunno if i spelled that right)
anyway, the best way to treat it is chemotherapy, and a bone marrow transplant. even though you might go into remission,that kind of cancer cant be "cured".
cancer is caused by stuff like radiation, some kinds of chemicals, and some kinds of viruses. (like they just found out that hpv causes cervical cancer). unfortunately, some cancers are also hereditary.
emphysema is caused, basically, by smoking tobacco, or sometimes, longterm exposure to breathing noxious chemicals. . its a nasty disease, that causes your chest to swell up, you cant breathe, , your lung tissue to rots away, and your fingers and toes get all clubby looking, because they don't get much oxygen. unfortunately, its irreversible. you cant really treat it. like, at all.
diabetes is commonly genetic... some families are at higher risk than others, but anyone who eats a poor diet and especially if they are overweight, can get it. especially in america, more and more kids are being diagnosed as "prediabetic", because of their weight, diet and family history. there are 2 types of diabetes, 1 and 2, so i dont wannna go into all that here. just go to web md and look them up or sthg. lol
there is also gestational diabetes, which means you only have it while you are pregnant, and have to stil to the normal diabetic diet, or the baby might grow too large and unhealthy before its born.
hope some of that helped.