Duchenne muscular dystrophy in a 4-year-old girl due to heterozygous frame shift deletion of the dystrophin gene and skewed X-inactivation

X-linked recessive diseases affect males, whereas female carriers are generally asymptomatic.We report on a 4-year-old girl who presented with a classical phenotype of Duchenne Muscular Dystrophy (DMD), a severe X-linked recessive type of muscular dystrophy affecting boys in early childhood.A thorough diagnostic work-up revealed that this resulted from a heterozygous out-of frame deletion in the DMD-gene in combination with an X-inactivation ratio of <10:90 in blood leukocytes and muscle.The case exemplifies that a skewed X-inactivation pattern has to be taken into account as mechanism causing clinical symptoms in female carriers of X-linked recessive disorders.