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.
The truth is, right now you really can't. Children usually don't start reading before the age of 5 or 6, and for good reason. Researchers believe that until that age, most children have not yet formed certain neural connections that allow them to decode printed letters and then mentally combine them to make words.