<prompt> Myotonic dystrophy is inherited in chromosomes -21201924  <response>: Myotonic dystrophy is associated with a trinucleotide CTG repeat expansion on chromosome 9.This expansion affects the mRNA for the dystrophila myotonia protein kinase DMPK.Myotonic dystrophy The characteristic feature of myotonic dystrophy is myotonia, i.e., the sustained involuntary contraction of a group of muscles.Of all the dystrophies, only myotonic dystrophy shows pathological changes in the intrafusal fibres of the muscle spindles.Extra-muscular abnormalities are : -Cataract Frontal baldnessGonadal atrophy DMDementia Decreased IgG 