Duchenne muscular dystrophy is a gonosomal recessive progressive disorder with the occurrence 1:3000. The clinical picture in boys-hemizygotes is very well known as the commonest myopathy. Less known is the fact that mild clinical features can occur in 10-20% of heterozygote carriers due to uneven lyonisation of the X chromosome. Authors refer the čase of an isolated occurrence of Duchenne muscular dystrophy in a girl, where diagnosis could be confirmed by the detection of a mosaic disturbance of dystrophin and a deletion in Dys-gene on Xp21.

        Key words: Duchenne muscular dystrophy, X linked inheritance, manifestation in a carrier girl, unequal lyonization