Most common reason for CPK to shoot up suddenly in a normal children is Viral myositis
. In other myopathies there is associated delay in motor milestones or regression of already aquired milestone.What i would like to know why was this test done in your child ?did he have muscle pain? was he not able to move around? did he have a recent viral fever?If so then probably its viral in onset he should get alright in few days.
Also you mentioned Social communication issues? could you elaborate on that.?If he is hyperactive and inattentive in school and not able to carry out instructions,wants to do many things at one time.Then he would require an evaluation from child psychologist
to rule out autistic spectrum disorders.