Muscular Distrpohy

My 29 year old son was diagnosed with Facioscapulohumeral Muscular Dystrophy.  I find it hard to believe that he has type of Muscular Distrophy. He was seen by a neurologist 4 years ago due to him having a problem walking and falling all the time.  Since he was a baby able to be put into a walker he has always walked on his toes (the instep of his foot) I was never too concerned about it because our doctor never gave me reason to be,  They just told me to keep reminding him to walk flat on his foot.  Over the years he this has caused him more problems with his walking and he began to start falling alot needing help to get up.  He was once told that he may have a short calf muscle, tendon ect. and that surgery could probably fix it.  He was sent for a blood test and fromt he test they have determined that due to a chromosome 4 he has FSHD.  I fid this hard to believe because he had not facial disorders.  No one in either of my or my husbands linage had ever had MD as far back as anyone can think of.  I do not deny the fact that his upper body is weak and may have some sort of MD but the lower half of his body is where most of his problem lies.  I would appreate any suggestions as to how he could be retested to be certain that he has beed diagnosed properly.