2027 ICD-10-CM Diagnosis Code A39.1Waterhouse-Friderichsen syndrome

ICD-10-CM Codes›A00–B99›A30-A49›A39

ICD-10-CM A39.1
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A39.1 is a billable ICD-10-CM diagnosis code for Waterhouse-Friderichsen syndrome. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 791, 793, 870 through 872. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 10 closely related codes. Coders also document this condition as adrenal hemorrhage. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Other specified and unspecified endocrine disorders.

A39.1 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 23 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 23, ESRD (V21) category 23, ESRD (V24) category 23, and RxHCC Part D (V08) category 43 for payment year 2027.

Code Identity

ICD-10-CM Code
A39.1
Billable Status
Yes — Valid for Submission
Code Describes
Waterhouse-Friderichsen syndrome
Short Description
Waterhouse-Friderichsen syndrome
Same as the full description in the CMS dataset.
Parent Code
A39
Meningococcal infection

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA39Meningococcal infection
This CodeA39.1Waterhouse-Friderichsen syndrome

Medicare Risk Adjustment (HCC)Billing

A39.1 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 23
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
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.

  • Adrenal hemorrhage
  • Adrenocortical hemorrhage
  • Waterhouse-Friderichsen syndrome

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A39.1: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

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.

  • Meningococcal hemorrhagic adrenalitis
  • Meningococcic adrenal syndrome

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.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A39.1, its category, or a range that includes it.

Excludes1 4

These codes carry an Excludes1 note naming A39.1: they are not reported together with it, unless the two conditions are unrelated.

  • E27.1 Primary adrenocortical insufficiency
    Waterhouse-Friderichsen syndrome (A39.1)
  • E27.4 Other and unspecified adrenocortical insufficiency
    Waterhouse-Friderichsen syndrome (A39.1)
  • E35 Disorders of endocrine glands in diseases classified elsewhere
    meningococcal hemorrhagic adrenalitis (A39.1)
  • E35 Disorders of endocrine glands in diseases classified elsewhere
    Waterhouse-Friderichsen syndrome (A39.1)

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 INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR END015
Other specified and unspecified endocrine disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Waterhouse-Friderichsen Syndrome

    a condition of hemorrhage and necrosis of the adrenal gland. it is characterized by rapidly developing adrenal insufficiency; hypotension; and widespread cutaneous purpura.

Patient EducationClinical

Adrenal Gland Disorders

Your adrenal glands are two small organs that sit on top of each kidney. The adrenal glands make different types of hormones you need to stay alive and healthy. Hormones are chemicals that travel in your bloodstream and control how different parts of your body work.

The full article covers:

  • What are adrenal glands?
  • What are adrenal gland disorders?
  • What causes adrenal gland disorders?
  • How are adrenal gland disorders diagnosed?
  • What are the treatments for adrenal gland disorders?

Read the full article at MedlinePlus

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

Convert A39.1 to ICD-9-CMHistory

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

ICD-9-CM
036.3 Meningococc adrenal synd
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 A39.1Overview

What is the ICD-10 code for Waterhouse-Friderichsen syndrome?

The ICD-10-CM code for Waterhouse-Friderichsen syndrome is A39.1 (sometimes written as A391). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A39.1 (Meningococcal infection) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Waterhouse-Friderichsen syndrome on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does A39.1 group to?

When Waterhouse-Friderichsen syndrome is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 872, 871, 870, with relative weights from 1.0066 to 6.9432 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A39.1 a CC or MCC?

CMS lists A39.1 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 10 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A39.1?

Under the General Equivalence Mappings, Waterhouse-Friderichsen syndrome converts to ICD-9-CM 036.3 (meningococc adrenal synd). The mapping is a direct match.

Does A39.1 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. A39.1 mapped to HCC 23 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 23 (Other Significant Endocrine and Metabolic Disorders), ESRD (V21) category 23 (Other Significant Endocrine and Metabolic Disorders), ESRD (V24) category 23 (Other Significant Endocrine and Metabolic Disorders), and RxHCC Part D (V08) category 43 (Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders).