2021 ICD-10-CM Code B27.91

Infectious mononucleosis, unspecified with polyneuropathy

Version 2021

Valid for Submission

B27.91 is a billable diagnosis code used to specify a medical diagnosis of infectious mononucleosis, unspecified with polyneuropathy. The code B27.91 is valid during the fiscal year 2021 from October 01, 2020 through September 30, 2021 for the submission of HIPAA-covered transactions.

The ICD-10-CM code B27.91 might also be used to specify conditions or terms like polyneuropathy due to infectious mononucleosis.

Unspecified diagnosis codes like B27.91 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

ICD-10:B27.91
Short Description:Infectious mononucleosis, unspecified with polyneuropathy
Long Description:Infectious mononucleosis, unspecified with polyneuropathy

Code Classification

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code B27.91 are found in the index:

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

Convert B27.91 to ICD-9 Code

The General Equivalency Mapping (GEM) crosswalk indicates an approximate mapping between the ICD-10 code B27.91 its ICD-9 equivalent. The approximate mapping means there is not an exact match between the ICD-10 code and the ICD-9 code and the mapped code is not a precise representation of the original code.

Information for Patients


Infectious Mononucleosis

Also called: Glandular fever, Kissing disease, Mono, Mononucleosis

Infectious mononucleosis, or "mono", is an infection usually caused by the Epstein-Barr virus. The virus spreads through saliva, which is why it's sometimes called "kissing disease." Mono occurs most often in teens and young adults. However, you can get it at any age. Symptoms of mono include

Sometimes you may also have a swollen spleen. Serious problems are rare.

A blood test can show if you have mono. Most people get better in two to four weeks. However, you may feel tired for a few months afterward. Treatment focuses on helping symptoms and includes medicines for pain and fever, warm salt water gargles and plenty of rest and fluids.


[Learn More in MedlinePlus]

Code History

  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016 (First year ICD-10-CM implemented into the HIPAA code set)