2024 ICD-10-CM Diagnosis Code A81.9

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Atypical virus infection of central nervous system, unspecified

  • A81.9 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
  • Short description: Atypical virus infection of central nervous system, unsp
  • The 2024 edition of ICD-10-CM A81.9 became effective on October 1, 2023.
  • This is the American ICD-10-CM version of A81.9 – other international versions of ICD-10 A81.9 may differ.

Applicable To

  • Prion diseases of the central nervous system NOS

The following code(s) above A81.9 contain annotation back-references

 that may be applicable to A81.9:

  • A00-B99  Certain infectious and parasitic diseases
  • A80-A89  Viral and prion infections of the central nervous system
  • A81  Atypical virus infections of central nervous system

Approximate Synonyms

  • Prion disease
  • Prion disease of central nervous system
  • Slow viral central nervous system infection
  • Slow virus infection of central nervous system

Clinical Information

  • A group of genetic, infectious, or sporadic degenerative human and animal nervous system disorders associated with abnormal prions. These diseases are characterized by conversion of the normal prion protein to an abnormal configuration via a post-translational process. In humans, these conditions generally feature dementia; ataxia; and a fatal outcome. Pathologic features include a spongiform encephalopathy without evidence of inflammation. The older literature occasionally refers to these as unconventional slow virus diseases. (from proc natl acad sci usa 1998 nov 10;95(23):13363-83)
  • Any of various brain diseases in humans and animals in which areas of the brain slowly degenerate and take on a spongy appearance.
  • Prion diseases, also termed transmissible spongiform encephalopathies (tses), are a group of fatal neurodegenerative diseases that affect humans and a number of other animal species. The etiology of these diseases is thought to be associated with the conversion of a normal protein, prpc, into an infectious, pathogenic form, prpsc. The conversion is induced by prion infections (for example, variant creutzfeldt-jakob disease (vcjd), iatrogenic cjd, kuru), mutations (familial cjd, gerstmann-straussler-scheinker syndrome, fatal familial insomnia (ffi)) or unknown factors (sporadic cjd (scjd)), and is thought to occur after prpc has reached the plasma membrane or is re-internalized for degradation. The prpsc form shows greater protease resistance than prpc and accumulates in affected individuals, often in the form of extracellular plaques. Pathways that may lead to neuronal death comprise oxidative stress, regulated activation of complement, ubiquitin-proteasome and endosomal-lysosomal systems, synaptic alterations and dendritic atrophy, corticosteroid response, and endoplasmic reticulum stress. In addition, the conformational transition could lead to the lost of a beneficial activity of the natively folded protein, prpc.

ICD-10-CM A81.9 is grouped within Diagnostic Related Group(s) (MS-DRG v41.0):

  • 056 Degenerative nervous system disorders with mcc
  • 057 Degenerative nervous system disorders without mcc
  • 974 Hiv with major related condition with mcc
  • 975 Hiv with major related condition with cc
  • 976 Hiv with major related condition without cc/mcc

Convert A81.9 to ICD-9-CMCode History

  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change
  • 2021 (effective 10/1/2020): No change
  • 2022 (effective 10/1/2021): No change
  • 2023 (effective 10/1/2022): No change
  • 2024 (effective 10/1/2023): No change

Code annotations containing back-references to A81.9:

  • Code First: F02

Diagnosis Index entries containing back-references to A81.9: