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.
By 24 months, your child should be able to communicate her immediate needs to you using words and starting to combining words (although not all of them will be entirely coherent). At this age, you'll understand your child's speech about 50 percent of the time.