ICD-10-CM 2027
ICD-10 code for Postencephalitic parkinsonism
From the official ICD-10-CM alphabetic index entry “Parkinsonism (idiopathic) (primary) › postencephalitic”. Page updated September 29, 2026.
About coding Postencephalitic parkinsonism
The ICD-10-CM code for Postencephalitic parkinsonism is G21.3 (Postencephalitic parkinsonism).
Within G21 (secondary parkinsonism), G21.3 is specifically for Postencephalitic parkinsonism. Related codes cover malignant neuroleptic syndrome (G21.0), other drug-induced secondary parkinsonism (G21.1), due to other external agents (G21.2), vascular parkinsonism (G21.4), other secondary parkinsonism (G21.8) and unspecified (G21.9).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 056 (Degenerative Nervous System Disorders with MCC, relative weight 2.2655) and DRG 057 (Degenerative Nervous System Disorders without MCC, relative weight 1.2838), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Common questions about Postencephalitic parkinsonism ICD-10 codes
What is the ICD-10 code for Postencephalitic parkinsonism?
- G21.3 — Postencephalitic parkinsonism.
Is G21.3 billable?
- Yes. G21.3 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G21.3 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G21.3 as a principal diagnosis.
Is G21.3 a CC or MCC?
- G21.3 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.