2027 ICD-10-CM Diagnosis Code E31.21Multiple endocrine neoplasia [MEN] type I

ICD-10-CM Codes›E00–E89›E20-E35›E31

ICD-10-CM E31.21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

E31.21 is a billable ICD-10-CM diagnosis code for multiple endocrine neoplasia [MEN] type I. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 643 through 645. Coders also document this condition as multiple endocrine neoplasia, type 1. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified endocrine disorders.

For Medicare Advantage risk adjustment, E31.21 maps to CMS-HCC Category 51 (Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders) under the V28 model, adding a risk factor of about 0.510 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
E31.21
Billable Status
Yes — Valid for Submission
Code Describes
Multiple endocrine neoplasia [MEN] type I
Short Description
Multiple endocrine neoplasia [MEN] type I
Same as the full description in the CMS dataset.
Parent Code
E31.2
Multiple endocrine neoplasia [MEN] syndromes

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE20-E35Disorders of other endocrine glands
CategoryE31Polyglandular dysfunction
This CodeE31.21Multiple endocrine neoplasia [MEN] type I

Medicare Risk Adjustment (HCC)Billing

E31.21 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.

CMS-HCC V28 Category (Payment Model)
HCC 51— Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders
Payment HCC · PY 2027 one of 11 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.510
community, non-dual, aged · ranges 0.313–0.654 across segments
Hierarchy
Top of its hierarchy
HCC 51 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
HCC 23
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 23 · ESRD (V21): HCC 23 · ESRD (V24): HCC 23
ESRD V21 weights: 0.013 dialysis, 0.234–0.359 functioning graft · ESRD V24 weights: 0.036 dialysis, 0.217–0.390 functioning graft
Part D (RxHCC)
RxHCC 43 — Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders
also risk-adjusts in the Part D prescription drug model (V08)

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.

  • Multiple endocrine neoplasia, type 1
  • Neoplasm of uncertain behavior of multiple endocrine glands
  • Polyglandular activity in multiple endocrine adenomatosis

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to E31.21: its own notes plus those printed at E31.2, E31, block E20-E35, and Chapter 4. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Wermer's syndrome

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From E31 Polyglandular dysfunction applies to 8 codes
  • ataxia telangiectasia [Louis-Bar] (G11.3)
  • dystrophia myotonica [Steinert] (G71.11)
  • pseudohypoparathyroidism (E20.1)
From Block E20-E35 Disorders of other endocrine glands applies to 99 codes
From Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases applies to 973 codes
  • transitory endocrine and metabolic disorders specific to newborn (P70-P74)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From E31.2 Multiple endocrine neoplasia [MEN] syndromes applies to 4 codes
  • any associated malignancies and other conditions associated with the syndromes

Notes

General instructions on how these codes are used.

From Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases applies to 973 codes
  • All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name E31.21, its category, or a range that includes it.

Excludes1 5

These codes carry an Excludes1 note naming E31.21: they are not reported together with it, unless the two conditions are unrelated.

  • D44 Neoplasm of uncertain behavior of endocrine glands
    multiple endocrine adenomatosis (E31.2-) names E31.2-, which includes this code
  • D44 Neoplasm of uncertain behavior of endocrine glands
    multiple endocrine neoplasia (E31.2-) names E31.2-, which includes this code
  • E31.1 Polyglandular hyperfunction
    multiple endocrine adenomatosis (E31.2-) names E31.2-, which includes this code
  • E31.1 Polyglandular hyperfunction
    multiple endocrine neoplasia (E31.2-) names E31.2-, which includes this code
  • Z15.81 Genetic susceptibility to multiple endocrine neoplasia [MEN]
    multiple endocrine neoplasia [MEN] syndromes (E31.2-) names E31.2-, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming E31.21: its condition is not part of those codes, and both may be reported when the patient has both.

  • QA1 Genetic disorders associated with neoplasms, not elsewhere classified
    multiple endocrine neoplasia [MEN] syndromes (E31.2-) names E31.2-, which includes this code

Code First 1

These codes say to code first a condition named in the note, and E31.21 is one of the conditions named.

  • G63 Polyneuropathy in diseases classified elsewhere
    endocrine disease, except diabetes (E00-E07, E15-E16, E20-E34) names E20-E34, which includes this code

Code Also 2

These codes say E31.21 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • C7A Malignant neuroendocrine tumors
    any associated multiple endocrine neoplasia [MEN] syndromes (E31.2-) names E31.2-, which includes this code
  • D3A Benign neuroendocrine tumors
    any associated multiple endocrine neoplasia [MEN] syndromes (E31.2-) names E31.2-, which includes this code

Notes 1

These notes mention E31.21.

  • Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases
    All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere. names E16-E31, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR END015
Other specified and unspecified endocrine disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Multiple Endocrine Neoplasia Type 1

    multiple endocrine neoplasia caused by inactivation of the tumor suppressor gene men-1. patients may develop hyperparathyroidism and parathyroid gland adenomas, pituitary gland adenomas, and neuroendocrine tumors.

Patient EducationClinical

Endocrine Diseases

Your endocrine system includes eight major glands throughout your body. These glands make hormones. Hormones are chemical messengers. They travel through your bloodstream to tissues or organs. Hormones work slowly and affect body processes from head to toe. These include:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert E31.21 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
258.01 Mult endo neoplas type I
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About E31.21Overview

What is the ICD-10 code for multiple endocrine neoplasia [MEN] type I?

The ICD-10-CM code for multiple endocrine neoplasia [MEN] type I is E31.21 (sometimes written as E3121). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is E31.21 (Multiple endocrine neoplasia [MEN] syndromes) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report multiple endocrine neoplasia [MEN] type I on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does E31.21 group to?

When multiple endocrine neoplasia [MEN] type I is the principal diagnosis on an inpatient stay, it groups to MS-DRG 644, 645, 643, with relative weights from 0.7461 to 1.6138 depending on complications. Higher weights mean higher Medicare reimbursement.

Can E31.21 be reported with G11.3?

Not as a rule. The Excludes1 note at E31, which applies to E31.21, lists "ataxia telangiectasia [Louis-Bar] (G11.3)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of E31.21?

Under the General Equivalence Mappings, multiple endocrine neoplasia [MEN] type I converts to ICD-9-CM 258.01 (mult endo neoplas type I). The mapping is a direct match.

What HCC is E31.21?

E31.21 (multiple endocrine neoplasia [MEN] type I) maps to CMS-HCC Category 51 (Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders), commonly written as HCC 51, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 23 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 43.

Does E31.21 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, E31.21 adds a risk adjustment factor of about 0.510 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.313 to 0.654 depending on the payment segment). HCC 51 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 51 category page.