ICD-10 Code G71.1 – Myotonic disorders (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G71.1 – Myotonic disorders
What it is
G71.1 identifies myotonic disorders, a group of neuromuscular conditions marked by delayed muscle relaxation after contraction. Use it when the record documents myotonia or a specific myotonic disorder.
Clinical signs
Common findings include muscle stiffness, difficulty releasing a grip, and delayed relaxation after voluntary movement. Clinical features vary; refer to documentation.
When to use this code
Use G71.1 when the provider diagnoses a myotonic disorder or documents myotonia as the primary neuromuscular problem. It may appear in neurology, genetics, or rehabilitation records. If the chart names a specific subtype, code that diagnosis if available and supported.
Do not use for
Do not use this code for general muscle weakness, cramps, or spasm without documented myotonia. Check documentation if the note describes another neuromuscular disease instead.
Coding tip
Confirm that the provider explicitly documents myotonia or a myotonic disorder before assigning G71.1.