ICD-9-CM diagnosis code (retired)
323.51 — Encephalitis and encephalomyelitis following immunization procedures
ICD-9-CM was replaced by ICD-10 on October 1, 2015. These are the ICD-10-CM equivalents from the CMS General Equivalence Mappings.
About ICD-9-CM 323.51
323.51 is an ICD-9-CM diagnosis code for encephalitis and encephalomyelitis following immunization procedures. ICD-9-CM was retired for U.S. claims on October 1, 2015, when ICD-10-CM took over.
The CMS General Equivalence Mappings translate it to 2 ICD-10-CM codes, such as G04.02 (Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis) and G04.32 (Postimmunization acute necrotizing hemorrhagic encephalopathy). All of these are approximate matches, so review the record to pick the right one.
ICD-10-CM equivalents
Common questions about 323.51
GEMs are a translation aid, not a substitute for coding from the record. The 2027 ICD-10 code set has changed since the last GEMs release in 2018. Page updated September 29, 2026.