2026 ICD-10-CM Diagnosis Code D89.44Hereditary alpha tryptasemia

ICD-10-CM Codes›D50–D89›D80-D89›D89

ICD-10-CM D89.44
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D89.44 is a billable ICD-10-CM diagnosis code for hereditary alpha tryptasemia. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 814 through 816. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.

D89.44 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 47 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 47, ESRD (V21) category 47, ESRD (V24) category 47, and RxHCC Part D (V08) category 99 for payment year 2026.

Code Identity

ICD-10-CM Code
D89.44
Billable Status
Yes — Valid for Submission
Code Describes
Hereditary alpha tryptasemia
Short Description
Hereditary alpha tryptasemia
Same as the full description in the CMS dataset.
Parent Code
D89.4
Mast cell activation syndrome and related disorders

Code Classification

ChapterD50–D89Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
SectionD80-D89Certain disorders involving the immune mechanism
CategoryD89Other disorders involving the immune mechanism, not elsewhere classified
This CodeD89.44Hereditary alpha tryptasemia

Medicare Risk Adjustment (HCC)Billing

D89.44 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 47
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 47 · ESRD (V21): HCC 47 · ESRD (V24): HCC 47
ESRD V21 weights: 0.097 dialysis, 0.549–0.688 functioning graft · ESRD V24 weights: 0.078 dialysis, 0.523–0.803 functioning graft
Part D (RxHCC)
RxHCC 99 — Immune Disorders
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 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.

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Use Additional Code

  • code, if applicable, for:
  • allergy status, other than to drugs and biological substances Z91.0
  • personal history of anaphylaxis Z87.892

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 BLD008
Immunity disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Code History & ChangesHistory

Replacement D89.44 replaces the following previously assigned code(s):

  • D89.49 - Other mast cell activation disorder
FY 2022AddedAdded to the ICD-10-CM code setEffective October 1, 2021.
FY 2023–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About D89.44Overview

What is the ICD-10 code for hereditary alpha tryptasemia?

The ICD-10-CM code for hereditary alpha tryptasemia is D89.44 (sometimes written as D8944). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is D89.44 (Mast cell activation syndrome and related disorders) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hereditary alpha tryptasemia on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does D89.44 group to?

When hereditary alpha tryptasemia is the principal diagnosis on an inpatient stay, it groups to MS-DRG 814, 815, 816, with relative weights from 0.6320 to 2.1267 depending on complications. Higher weights mean higher Medicare reimbursement.

Does D89.44 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. D89.44 mapped to HCC 47 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 47 (Disorders of Immunity), ESRD (V21) category 47 (Disorders of Immunity), ESRD (V24) category 47 (Disorders of Immunity), and RxHCC Part D (V08) category 99 (Immune Disorders).