2026 ICD-10-CM Diagnosis Code D81.6Major histocompatibility complex class I deficiency
ICD-10-CM Codes›D50–D89›D80-D89›D81
- Billable — Valid for Submission
- Chronic Condition
D81.6 is a billable ICD-10-CM diagnosis code for major histocompatibility complex class I deficiency. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 808 through 810. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Major histocompatibility complex class I deficiency
- Major histocompatibility complex class I deficiency due to B2M mutation
- Major histocompatibility complex class I deficiency due to TAP1 mutation
- Major histocompatibility complex class I deficiency due to TAP2 mutation
- Major histocompatibility complex class I deficiency due to TAPBP mutation
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Bare lymphocyte syndrome
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- major histocompatibility complex
- class I - D81.6
- Syndrome - See Also: Disease;
- bare lymphocyte - D81.6
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Deficiency, deficient
- major histocompatibility complex
- class I
- Syndrome
- bare lymphocyte
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Immune System and Disorders
Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.
The full article covers:
- What is the immune system?
- What are the parts of the immune system?
- How does the immune system work?
- What are the types of immunity?
- What can go wrong with the immune system?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert D81.6 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About D81.6Overview
Is D81.6 (Combined immunodeficiencies) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report major histocompatibility complex class I deficiency on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does D81.6 group to?
When major histocompatibility complex class I deficiency is the principal diagnosis on an inpatient stay, it groups to MS-DRG 808, 809, 810, with relative weights from 1.0466 to 2.2079 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of D81.6?
Under the General Equivalence Mappings, major histocompatibility complex class I deficiency converts to ICD-9-CM 279.2 (combined immunity defic). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:
- The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
- The condition places limitations on self-care, independent living, and social interactions.
