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.
Children generally understand more words than they use in writing and speaking, and they speak more words than they can read. In order to help your 7 year old increase his or her reading vocabulary, you can make sure your child knows sight words, or words that can be recognized immediately without sounding them out.