Myotonic muscular dystrophy

This code represents myotonic muscular dystrophy type 1 (DM1), also known as Steinert's disease, which is the most common form of adult-onset muscular dystrophy. It is a chronic, inherited, multisystem disorder characterized by progressive muscle wasting and weakness, myotonia (delayed muscle relaxation), and often involves other organ systems such as the heart, eyes, and endocrine system.

Use this code for patients diagnosed with myotonic muscular dystrophy type 1, confirmed by clinical presentation and/or genetic testing. Documentation should clearly indicate the diagnosis of myotonic dystrophy, often specifying type 1, and may include details of associated systemic manifestations. This code is appropriate for initial diagnosis and subsequent encounters for management of the condition.

• Ensure documentation specifies "myotonic" muscular dystrophy to differentiate from other forms.
• Do not confuse with other types of muscular dystrophy, such as Duchenne or Becker, which have different codes.
• Code any associated systemic manifestations (e.g., cardiac arrhythmias, cataracts, diabetes mellitus) separately as secondary diagnoses.