Sickle Cell Trait is not a lesser form of, and cannot turn into, Sickle Cell Disease. You are born with one or the other.
In some cases, extreme conditions can cause red blood cells to “sickle” and create similar, but mostly milder, symptoms compared to Sickle Cell Disease. Most conditions have to do with blood flow and oxygen within the body and again are seen usually only in more extreme cases. Some examples of these extreme cases include the following: severe dehydration, extremely strenuous activity, and high altitudes. Although symptoms are not common and usually milder in those with SCT compared to those with SCD, these kinds of situations can cause the red blood cells to become deformed and disrupt blood flow to important regions of the body.