D89.41 (Monoclonal mast cell activation syndrome) compared with Q82.2 (Congenital cutaneous mastocytosis), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Not coded here — these two are mutually exclusive.
“congenital cutaneous mastocytosis (Q82.2)”
An Excludes1 note means the two conditions cannot occur together, so the pair should not be reported for the same encounter. The sole exception is when the conditions are documented as unrelated to each other.
Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a
No — do not report together. D89.41 carries an Excludes1 note covering Q82.2: “congenital cutaneous mastocytosis (Q82.2)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
| D89.41Monoclonal mast cell activation syndrome | Q82.2Congenital cutaneous mastocytosis | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | D50-D89 — Diseases of the Blood and Blood-forming Organs and Certain Disorders Involving the Immune Mechanism (D50-D89) | Q00-Q99 — Congenital Malformations, Deformations and Chromosomal Abnormalities (Q00-Q99) |
| Definition | Monoclonal mast cell activation syndrome is a billable ICD-10-CM diagnosis code (D89.41). | Congenital cutaneous mastocytosis is a billable ICD-10-CM diagnosis code (Q82.2). |
| Includes | defects in the complement system immunodeficiency disorders, except human immunodeficiency virus [HIV] disease sarcoidosis | Congenital diffuse cutaneous mastocytosis Congenital maculopapular cutaneous mastocytosis Congenital urticaria pigmentosa |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources