ICD-10 Code G71.12 – Myotonia congenita (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G71.12 – Myotonia congenita
What it is
G71.12 identifies myotonia congenita, an inherited muscle disorder that causes delayed relaxation after contraction. Use it when the record documents this specific diagnosis.
Clinical signs
Typical findings include muscle stiffness, especially after rest, and difficulty releasing a grip or starting movement. Clinical features vary; refer to documentation.
When to use this code
Use G71.12 when the clinician clearly documents myotonia congenita, including inherited or congenital myotonia of this type. It may appear in neurology notes, problem lists, or discharge summaries. Code it only when the diagnosis is established, not merely suspected.
Do not use for
Do not use this code for general muscle cramps, nonspecific stiffness, or other neuromuscular disorders without documentation of myotonia congenita. Check documentation if the exact subtype is unclear.
Coding tip
Confirm the provider names the condition as myotonia congenita before assigning G71.12.