Myotonic Dystrophy

Key points

• Myotonic dystrophy Myotonic dystrophy (also called dystrophia myotonica) is an inherited myopathy with features developing at around 20-30 years old. It affects skeletal, cardiac and smooth muscle.
• autosomal dominant
• a trinucleotide repeat disorder
• DM1 is caused by a CTG repeat at the end of the DMPK (Dystrophia Myotonica-Protein Kinase) gene on chromosome 19
• DM2 is caused by a repeat expansion of the ZNF9 gene on chromosome 3 The key differences are listed in table below: DM1 DM2 - DMPK gene on chromosome - ZNF9 gene on chromosome 3 - Proximal weakness more prominent - Distal…