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ICD-10-CM 2027 diagnosis code

G71.12Myotonia congenita

✓ Billable / specific

G71.12 is a valid, billable ICD-10-CM code for myotonia congenita. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G71.12

G71.12 is the ICD-10-CM diagnosis code for myotonia congenita. It belongs to category G71 (primary disorders of muscles), block G70-G73 (diseases of myoneural junction and muscle) and chapter 6 (diseases of the nervous system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within G71.1 (myotonic disorders), G71.12 is specifically for myotonia congenita. Related codes cover myotonic muscular dystrophy (G71.11), myotonic chondrodystrophy (G71.13), drug induced myotonia (G71.14) and other specified myotonic disorders (G71.19).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 091 (Other Disorders of Nervous System with MCC, relative weight 1.7046), DRG 092 (Other Disorders of Nervous System with CC, relative weight 1.0239) and DRG 093 (Other Disorders of Nervous System without CC/MCC, relative weight 0.7783), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 359.22 (myotonia congenita).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Acetazolamide responsive myotonia congenita
  • Dominant myotonia congenita [Thomsen disease]
  • Myotonia levior
  • Recessive myotonia congenita [Becker disease]

Notes that apply from higher levels

Instructions written at a parent level also apply to G71.12.

› From G71 Primary disorders of muscles
Excludes2
  • arthrogryposis multiplex congenita (Q74.3)
  • metabolic disorders (E70-E88)
  • myositis (M60.-)

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Alphabetic index entries

6 entries

Terms in the official ICD-10-CM index that lead to G71.12.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about G71.12

Is G71.12 billable?

Yes. G71.12 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can G71.12 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict G71.12 as a principal diagnosis.

Is G71.12 a CC or MCC?

No. G71.12 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does G71.12 group to?

G71.12 is used in the MS-DRG v44.0 logic for MS-DRG 091 (Other Disorders of Nervous System with MCC), MS-DRG 092 (Other Disorders of Nervous System with CC) and MS-DRG 093 (Other Disorders of Nervous System without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for G71.12?

The CMS General Equivalence Mappings map G71.12 to ICD-9-CM 359.22.