BackgroundApproximately one-third of new cases of Duchenne muscular dystrophy (DMD) can be attributed to sporadically arising new mutations, however in the majority of cases the DMD mutation has been inherited from the mother. These female carriers can have either a constitutive or mosaic mutation.AimThe aim of this study was to determine the segregation of the at-risk haplotype and to find a deletion in the dystrophin gene of patients.MethodWe analyzed individuals from two families with a history of DMD in order to predict the carrier status ofrelatedfemales. In one of these cases the mother had two affected sons, while in the other one son and two grandchildren were affected; therefore we predict that the mother would be an obligatory carrier.ResultsHaplotype analysis of theDMDloci revealed that in the two families both the healthy and affected brothers had inherited the same X maternal chromosome. However, the affected brother carried a deletion, which was absent in the unaffected sibling.ConclusionThese findings suggested that the mothers in the two families were germline mosaics for theDMDgene. The results of this study demonstrate the usefulness of the methodology that combine the haplotype analysis with the identification of the mutation in order to detect hidden germline mosaicisms and, thus, improve genetic counseling.