It is possible that the main title of the report Marfan Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
As Jenny points out, being able to lisp the alphabet song at age two has little to do with 'knowing' the alphabet. And, yes, most children learn the letters by sight and sound in kindergarten, although most are capable of learning this information sooner if diligently taught by parents or others.
Preschoolers: Ages 2-5. Between ages two and three, many preschoolers begin to use more complicated sentences. However, this does not mean that they understand all of an adult's words or abstract concepts. In fact, preschoolers are often very literal thinkers and interpret ideas concretely.