2027 ICD-10-CM Diagnosis Code E80.21Acute intermittent (hepatic) porphyria
ICD-10-CM Codes›E00–E89›E70-E88›E80
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 50
- Chronic Condition
E80.21 is a billable ICD-10-CM diagnosis code for acute intermittent (hepatic) porphyria. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 642. 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 35 closely related codes. Coders also document this condition as acute intermittent porphyria. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified nutritional and metabolic disorders.
For Medicare Advantage risk adjustment, E80.21 maps to CMS-HCC Category 50 (Amyloidosis, Porphyria, and Other Specified Metabolic Disorders) under the V28 model, adding a risk factor of about 0.648 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
E80.21 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.
- Acute intermittent porphyria
- Homozygous acute intermittent porphyria
- Porphobilinogen deaminase deficiency
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to E80.21: its own notes plus those printed at E80, block E70-E88, and Chapter 4. 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.
- defects of catalase and peroxidase
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
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.
- Ehlers-Danlos syndromes (Q79.6-)
Notes
General instructions on how these codes are used.
- 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.
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.
Clinical InformationClinical
Porphyria, Acute Intermittent
an autosomal dominant porphyria that is due to a deficiency of hydroxymethylbilane synthase in the liver, the third enzyme in the 8-enzyme biosynthetic pathway of heme. clinical features are recurrent and life-threatening neurologic disturbances, abdominal pain, and elevated level of aminolevulinic acid and porphobilinogen in the urine.
Patient EducationClinical
Porphyria
Porphyrias are a group of genetic disorders caused by problems with how your body makes a substance called heme. Heme is found throughout the body, especially in your blood and bone marrow, where it carries oxygen.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert E80.21 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About E80.21Overview
What is the ICD-10 code for acute intermittent (hepatic) porphyria?
The ICD-10-CM code for acute intermittent (hepatic) porphyria is E80.21 (sometimes written as E8021). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is E80.21 (Other and unspecified porphyria) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report acute intermittent (hepatic) porphyria on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does E80.21 group to?
When acute intermittent (hepatic) porphyria is the principal diagnosis on an inpatient stay, it groups to MS-DRG 642 (inborn and Other Disorders of Metabolism), which carries a relative weight of 1.3226. Higher weights mean higher Medicare reimbursement.
Is E80.21 a CC or MCC?
CMS lists E80.21 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 35 closely related codes in its exclusion list.
Can E80.21 be reported with a code from E34.5?
Not as a rule. The Excludes1 note at block E70-E88, which applies to E80.21, lists "androgen insensitivity syndrome (E34.5-)". 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 HCC is E80.21?
E80.21 (acute intermittent (hepatic) porphyria) maps to CMS-HCC Category 50 (Amyloidosis, Porphyria, and Other Specified Metabolic Disorders), commonly written as HCC 50, 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 E80.21 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, E80.21 adds a risk adjustment factor of about 0.648 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.362 to 0.883 depending on the payment segment). HCC 50 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 50 category page.
