D89.834 vs M35.9
D89.834 (Cytokine release syndrome, grade 4) compared with M35.9 (Systemic involvement of connective tissue, unspecified), 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. D89.834 carries an Excludes1 note covering M35.9: “autoimmune disease (systemic) NOS (M35.9)”
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
| D89.834Cytokine release syndrome, grade 4 | M35.9Systemic involvement of connective tissue, unspecified | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | D50-D89 — Diseases of the Blood and Blood-forming Organs and Certain Disorders Involving the Immune Mechanism (D50-D89) | M00-M99 — Diseases of the Musculoskeletal System and Connective Tissue (M00-M99) |
| Definition | Cytokine release syndrome, grade 4 is a billable ICD-10-CM diagnosis code (D89.834). | Systemic involvement of connective tissue, unspecified is a billable ICD-10-CM diagnosis code (M35.9). |
| Includes | defects in the complement system immunodeficiency disorders, except human immunodeficiency virus [HIV] disease sarcoidosis | autoimmune disease NOS collagen (vascular) disease NOS systemic autoimmune disease systemic collagen (vascular) disease |
| Use additional code | code for adverse effect, if applicable, to identify immune checkpoint inhibitors and immunostimulant drugs (T45.AX5) code to identify associated manifestations | — |
| Code first | underlying cause, such as: complications following infusion, transfusion and therapeutic injection (T80.89-) | — |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources