D89.40 vs R77.1
D89.40 (Mast cell activation, unspecified) compared with R77.1 (Abnormality of globulin), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Can these codes be reported together?
No — do not report together. D89.40 carries an Excludes1 note covering R77.1: “hyperglobulinemia NOS (R77.1)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
Side by side
| D89.40Mast cell activation, unspecified | R77.1Abnormality of globulin | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | D50-D89 — Diseases of the Blood and Blood-forming Organs and Certain Disorders Involving the Immune Mechanism (D50-D89) | R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99) |
| Definition | Mast cell activation, unspecified is a billable ICD-10-CM diagnosis code (D89.40). | Abnormality of globulin is a billable ICD-10-CM diagnosis code (R77.1). |
| Includes | defects in the complement system immunodeficiency disorders, except human immunodeficiency virus [HIV] disease sarcoidosis Mast cell activation disorder, unspecified | Hyperglobulinemia NOS |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources