D89.4

Mast cell activation syndrome and related disorders

FY2027Chapter 3: Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism/D80–D89 Certain disorders involving the immune mechanism

Non-billable headerNot valid on its own. Use one of the more specific codes under it.

Excludes1
Excludes2

D89.4 is a non-billable ICD-10-CM code header for mast cell activation syndrome and related disorders. Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. The more specific codes under it are D89.40 Mast cell activation, unspecified; D89.41 Monoclonal mast cell activation syndrome; D89.42 Idiopathic mast cell activation syndrome; D89.43 Secondary mast cell activation and 2 more. Its coding notes include 15 Excludes1 entries and 11 Excludes2 entries.

Excludes1

Not coded here. The listed conditions generally should not be reported together.

This code

aggressive systemic mastocytosis (C96.21)
congenital cutaneous mastocytosis (Q82.2)
(non-congenital) cutaneous mastocytosis (D47.01)
(indolent) systemic mastocytosis (D47.02)
malignant mast cell neoplasm (C96.2-)
malignant mastocytoma (C96.29)
mast cell leukemia (C94.3-)
mast cell sarcoma (C96.22)
mastocytoma NOS (D47.09)
other mast cell neoplasms of uncertain behavior (D47.09)
systemic mastocytosis associated with a clonal hematologic non-mast cell lineage disease (SM-AHNMD) (D47.02)

Inherited from D89 Other disorders involving the immune mechanism, not elsewhere classified

hyperglobulinemia NOS (R77.1)
monoclonal gammopathy (of undetermined significance) (D47.2)

Also from chapter/block level (2 notes)

Inherited from D80–D89 Certain disorders involving the immune mechanism

autoimmune disease (systemic) NOS (M35.9)
functional disorders of polymorphonuclear neutrophils (D71-)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Inherited from D89 Other disorders involving the immune mechanism, not elsewhere classified

transplant failure and rejection (T86.-)

Also from chapter/block level (10 notes)

Inherited from D80–D89 Certain disorders involving the immune mechanism

human immunodeficiency virus [HIV] disease (B20)

Inherited from Chapter 3 Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism

autoimmune disease (systemic) NOS (M35.9)
certain conditions originating in the perinatal period (P00-P96)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
human immunodeficiency virus [HIV] disease (B20)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Includes

Further defines or gives examples of the content of the category.

Also from chapter/block level (3 notes)

Inherited from D80–D89 Certain disorders involving the immune mechanism

defects in the complement system
immunodeficiency disorders, except human immunodeficiency virus [HIV] disease
sarcoidosis

More specific codes under D89.4 6