D89.834 Cytokine release syndrome, grade 4

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

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

Excludes1 (never code together)

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

Excludes2 (not included here)

• transplant failure and rejection (T86.-)

Applies from D89.83 Cytokine release syndrome

Code first

• underlying cause, such as:
• complications following infusion, transfusion and therapeutic injection (T80.89-)
• complications of transplanted organs and tissue (T86.-)

Use additional code

• code for adverse effect, if applicable, to identify immune checkpoint inhibitors and immunostimulant drugs (T45.AX5)
• code to identify associated manifestations

MS-DRG index

Defines the logic of DRG(s) 814-816 in MDC 16.

Medicare Code Edits (MCE v43.1 (April 2026))

• Unacceptable principal diagnosis: These codes describe a circumstance which influences care but is not a current illness or injury, or capture only an underlying condition, and are unacceptable as principal diagnosis.

Code annotations containing back-references to D89.834

Back-references to D89.83

• Use Additional: T80.82 Complication of immune effector cellular therapy ("cytokine release syndrome (D89.83-)")

Back-references to D89

• Type 1 Excludes: D72 Other disorders of white blood cells ("immunity disorders (D80-D89)")

Diagnosis Index entries for D89.834

• Syndrome › cytokine release › grade 4

Nearby codes

• D89.82 Autoimmune lymphoproliferative syndrome [ALPS]
• D89.83 Cytokine release syndrome
• D89.831 Cytokine release syndrome, grade 1
• D89.832 Cytokine release syndrome, grade 2
• D89.833 Cytokine release syndrome, grade 3
• D89.834 Cytokine release syndrome, grade 4 (this code)
• D89.835 Cytokine release syndrome, grade 5
• D89.839 Cytokine release syndrome, grade unspecified
• D89.84 IgG4-related disease
• D89.89 Other specified disorders involving the immune mechanism, not elsewhere classified
• D89.9 Disorder involving the immune mechanism, unspecified