Yes. A39.1 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. A39.1 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for A39.1?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. A39.1 was a payment HCC under V24 (Other Significant Endocrine and Metabolic Disorders) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting A39.1?

This code should be used only when meningococcal septicemia with acute adrenal insufficiency and hemorrhage is documented; verify the meningococcal etiology is confirmed in the medical record This condition is often fatal and may be coded alongside sepsis codes (A39.0) and other complications; ensure all documented manifestations including DIC, shock, and organ failure are captured with appropriate additional codes Because A39.1 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

A39.1: Waterhouse-Friderichsen syndrome — ICD-10 | Other Significant Endocrine and Metabolic

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupA39.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other bacterial diseases (A30-A49)

A39.1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Waterhouse-Friderichsen syndrome

Waterhouse-Friderichsen syndrome is a life-threatening condition caused by meningococcal infection that leads to severe bleeding and failure of the adrenal glands. This rare but critical complication typically develops rapidly and requires immediate emergency treatment.

Buddy Insight

Waterhouse-Friderichsen syndrome is a catastrophic adrenal hemorrhagic necrosis most commonly caused by fulminant meningococcal septicemia.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.230

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 23

Other Significant Endocrine a...

RAF 0.0

RXHCC

Mapped

HCC 43

Other Significant Endocrine a...

RAF 0.0

Code Trumping

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Code Book Path

Official

A39Meningococcal infection

A39.1Waterhouse-Friderichsen syndrome

Inclusion Terms

Official

Meningococcal hemorrhagic adrenalitis
Meningococcic adrenal syndrome

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for A39.1 in this effective period.

Related Child Codes

Official

A39.0Meningococcal meningitis

A39.2Acute meningococcemia

A39.3Chronic meningococcemia

A39.4Meningococcemia, unspecified

A39.5Meningococcal heart disease

Includes

Official

ICD-10-CM does not list Includes notes for A39.1 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for A39.1 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for A39.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for A39.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A39.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical triad: purpura fulminans, DIC, and acute adrenal insufficiency

Laboratory evidence of adrenal insufficiency (low cortisol, electrolyte abnormalities)

Coagulation studies showing DIC (elevated D-dimer, prolonged PT/PTT, low fibrinogen, thrombocytopenia)

Blood cultures or clinical evidence of meningococcal infection

MEAT Support

HCC Buddy guidance

Clinical triad: purpura fulminans, DIC, and acute adrenal insufficiency

Laboratory evidence of adrenal insufficiency (low cortisol, electrolyte abnormalities)

Coagulation studies showing DIC (elevated D-dimer, prolonged PT/PTT, low fibrinogen, thrombocytopenia)

Blood cultures or clinical evidence of meningococcal infection

Audit Caution

HCC Buddy guidance

While classically associated with meningococcal infection, Waterhouse-Friderichsen can be caused by other organisms — A39.1 should only be used for the meningococcal form

DIC (D65) should be coded as an additional diagnosis — A39.1 does not capture the coagulopathy

Do not forget to code septic shock (R65.21) when hemodynamic instability is present, which is nearly universal in this condition

Common Mistakes

HCC Buddy guidance

A39.2 (Acute meningococcemia) — A39.2 is meningococcal bloodstream infection without the adrenal hemorrhage syndrome; A39.1 specifically captures the adrenal crisis

E27.2 (Addisonian crisis) — A39.1 is the combination code for meningococcal-induced adrenal crisis; do not use E27.2 separately

D65 (Disseminated intravascular coagulation) — DIC in Waterhouse-Friderichsen should still be coded separately with D65 in addition to A39.1

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is A39.1 an HCC code?

Yes. A39.1 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.

HCC Category Mapping

V24HCC 23, Other Significant Endocrine and Metabolic Disorders

0.230

ESRDHCC 23, Other Significant Endocrine and Metabolic Disorders

0.000

RxHCCHCC 43, Other Significant Endocrine and Metabolic Disorders

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work A39.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for A39.1

For A39.1to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed A39.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

A39.1 is the ICD-10-CM diagnosis code for waterhouse-friderichsen syndrome. Waterhouse-Friderichsen syndrome is a life-threatening condition caused by meningococcal infection that leads to severe bleeding and failure of the adrenal glands. This rare but critical complication typically develops rapidly and requires immediate emergency treatment. A39.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).

Under the older CMS-HCC V24 model, A39.1 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.230. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This code should be used only when meningococcal septicemia with acute adrenal insufficiency and hemorrhage is documented; verify the meningococcal etiology is confirmed in the medical record. Because A39.1 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A39.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This code should be used only when meningococcal septicemia with acute adrenal insufficiency and hemorrhage is documented; verify the meningococcal etiology is confirmed in the medical record
•This condition is often fatal and may be coded alongside sepsis codes (A39.0) and other complications; ensure all documented manifestations including DIC, shock, and organ failure are captured with appropriate additional codes

Clinical Significance

Waterhouse-Friderichsen syndrome is a catastrophic adrenal hemorrhagic necrosis most commonly caused by fulminant meningococcal septicemia. It presents with rapidly progressive purpura fulminans, DIC, and acute bilateral adrenal gland destruction leading to acute adrenal insufficiency and cardiovascular collapse. Mortality is extremely high even with aggressive treatment.

Documentation Requirements

✓Clinical triad: purpura fulminans, DIC, and acute adrenal insufficiency
✓Laboratory evidence of adrenal insufficiency (low cortisol, electrolyte abnormalities)
✓Coagulation studies showing DIC (elevated D-dimer, prolonged PT/PTT, low fibrinogen, thrombocytopenia)
✓Blood cultures or clinical evidence of meningococcal infection
✓Imaging of adrenal glands (CT showing bilateral adrenal hemorrhage) when available

Commonly Confused Codes

•A39.2 (Acute meningococcemia): A39.2 is meningococcal bloodstream infection without the adrenal hemorrhage syndrome; A39.1 specifically captures the adrenal crisis
•E27.2 (Addisonian crisis): A39.1 is the combination code for meningococcal-induced adrenal crisis; do not use E27.2 separately
•D65 (Disseminated intravascular coagulation): DIC in Waterhouse-Friderichsen should still be coded separately with D65 in addition to A39.1