Yes, you can be diagnosed with ALL followed by AML. ALL is the cancer of lymphocytes whereas AML is the cancer of the myelocytes. It can be diagnosed together (Biphenotypic leukemia) or separately.
A history of diseases that damage the bone marrow, such as a plastic anemia , or a history of cancers of the lymphatic system puts people at a high risk
There are a number of different kinds of leukemia, and they may have different causes. What is clear is that the causes of leukemia are unclear. There are some good arguments made for increased risk...