2027 ICD-10-CM Diagnosis Code G71.21Nemaline myopathy
ICD-10-CM Codes›G00–G99›G70-G73›G71
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 197
- Chronic Condition
G71.21 is a billable ICD-10-CM diagnosis code for nemaline myopathy. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 91 through 93. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 22 closely related codes. Coders also document this condition as amish nemaline myopathy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Myopathies.
For Medicare Advantage risk adjustment, G71.21 maps to CMS-HCC Category 197 (Muscular Dystrophy) under the V28 model, adding a risk factor of about 0.426 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
G71.21 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Amish nemaline myopathy
- Childhood-onset nemaline myopathy
- Intermediate nemaline myopathy
- Nemaline myopathy
- Nemaline myopathy, early onset type
- Nemaline myopathy, late onset type
- Progressive weakness of muscle
- Severe congenital nemaline myopathy
- Typical nemaline myopathy
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G71.21: its own notes plus those printed at G71.2, G71, and Chapter 6. A note printed at a category, block or chapter applies to every code under it.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name G71.21, its category, or a range that includes it.
Excludes2 1
These codes carry an Excludes2 note naming G71.21: its condition is not part of those codes, and both may be reported when the patient has both.
- Block M60-M63 Disorders of muscles
Code First 1
These codes say to code first a condition named in the note, and G71.21 is one of the conditions named.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
nemaline body G71.21
rod body G71.21
nemaline G71.21
rod (body) G71.21
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Myopathies, Nemaline
a group of inherited congenital myopathic conditions characterized clinically by weakness, hypotonia, and prominent hypoplasia of proximal muscles including the face. muscle biopsy reveals large numbers of rod-shaped structures beneath the muscle fiber plasma membrane. this disorder is genetically heterogeneous and may occasionally present in adults. (adams et al., principles of neurology, 6th ed, p1453)
Patient EducationClinical
Nemaline myopathy
Nemaline myopathy is a disorder that primarily affects skeletal muscles, which are muscles that the body uses for movement.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Code History & ChangesHistory
Replacement G71.21 replaces the following previously assigned code(s):
- G71.2 - Congenital myopathies
Questions About G71.21Overview
What is the ICD-10 code for nemaline myopathy?
The ICD-10-CM code for nemaline myopathy is G71.21 (sometimes written as G7121). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is G71.21 (Congenital myopathies) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report nemaline myopathy on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G71.21 group to?
When nemaline myopathy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 91, 92, 93, with relative weights from 0.7783 to 1.7050 depending on complications. Higher weights mean higher Medicare reimbursement.
Is G71.21 a CC or MCC?
CMS lists G71.21 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 22 closely related codes in its exclusion list.
What HCC is G71.21?
G71.21 (nemaline myopathy) maps to CMS-HCC Category 197 (Muscular Dystrophy), commonly written as HCC 197, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 76 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does G71.21 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, G71.21 adds a risk adjustment factor of about 0.426 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.145 to 0.681 depending on the payment segment). HCC 197 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 197 category page.
