D89.4
Mast cell activation syndrome and related disorders
Not billable — category only FY2026 2025-10-01 → 2026-09-30
Exclusions 26 never code together
D89.4code
Excludes1
- aggressive systemic mastocytosis (C96.21)C96.21C96.21
- congenital cutaneous mastocytosis (Q82.2)Q82.2Q82.2
- (non-congenital) cutaneous mastocytosis (D47.01)D47.01D47.01
- (indolent) systemic mastocytosis (D47.02)D47.02D47.02
- malignant mast cell neoplasm (C96.2-)C96.2-C96.2-
- malignant mastocytoma (C96.29)C96.29C96.29
- mast cell leukemia (C94.3-)C94.3-C94.3-
- mast cell sarcoma (C96.22)C96.22C96.22
- mastocytoma NOS (D47.09)D47.09D47.09
- other mast cell neoplasms of uncertain behavior (D47.09)D47.09D47.09
- systemic mastocytosis associated with a clonal hematologic non-mast cell lineage disease (SM-AHNMD) (D47.02)D47.02D47.02
D89code
D80-D89block
D50-D89chapter
Excludes2
- autoimmune disease (systemic) NOS (M35.9)M35.9
- certain conditions originating in the perinatal period (P00-P96)P00-P96
- complications of pregnancy, childbirth and the puerperium (O00-O9A)O00-O9A
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Q00-Q99
- endocrine, nutritional and metabolic diseases (E00-E88)E00-E88
- human immunodeficiency virus [HIV] disease (B20)B20
- injury, poisoning and certain other consequences of external causes (S00-T88)S00-T88
- neoplasms (C00-D49)C00-D49
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)R00-R94
Excludes1 — never code together. The excluded condition and this one are mutually exclusive.
Excludes2 — not included here, but the patient may have both. Code both when documented.
Instructional notes 3
D80-D89block
Includes
- defects in the complement system
- immunodeficiency disorders, except human immunodeficiency virus [HIV] disease
- sarcoidosis
Index entries leading here filed at null
No alphabetic index entry points at this code.
Alongside this code 6 same parent — D89
Subordinate codes 6
Medications 5
5 Mast Cell Activation Disorders drugs 41 Bipolar and Related Disorders drugs 20 Narcotic-Related Disorders drugs 19 Trauma and Stressor Related Disorders drugs 10 Feeding and Eating Disorders drugs
MED-RT files conditions by MeSH, which carves the world differently from ICD-10. These are name matches on this code's description, offered as candidates — not as an assertion that they are this code.
Additional references
AHA Coding Clinic® Licence required
Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.