A 6yrs old boy,second child of a non consangous marriage,(has an 9yrs old brother,normal)presented with weakness,repeated falls while walking, lumber lordosis, wadling gait and positive Gower sign for last four months.Also there is history of ?mild/moderate birth asphyxia and delayed motor mile stones.(now the in telligence is normal)On examination there is no sensory involvement. Child has a characterstic marfanoid facies(dolicephaly,high arched palate, thin long extremities etc).Mother also tells about repeated chest infections during infancy and childhood.CPK=8625I.U./dl, muscle biopsy:fraying of muscle fibres,internalisation of nuclei and variation in size of muscle fibres.No family history of similar illness . PL help in making an definative diagnosis.