B27.91 ICD-10-CM Code: Infectious mononucleosis, unspecified with polyneuropathy
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other viral diseases (B25-B34)
B27.91
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceInfectious mononucleosis, unspecified with polyneuropathy
This code describes infectious mononucleosis (commonly called 'mono' or the 'kissing disease') caused by the Epstein-Barr virus, with an additional complication of polyneuropathy, which is nerve damage affecting multiple nerves throughout the body. The polyneuropathy is a less common but serious complication of the viral infection.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for B27.91 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for B27.91 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for B27.91 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for B27.91 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for B27.91 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for B27.91 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for B27.91 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is B27.91 an HCC code?
No. B27.91 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
B27.91 is the ICD-10-CM diagnosis code for infectious mononucleosis, unspecified with polyneuropathy. This code describes infectious mononucleosis (commonly called 'mono' or the 'kissing disease') caused by the Epstein-Barr virus, with an additional complication of polyneuropathy, which is nerve damage affecting multiple nerves throughout the body. The polyneuropathy is a less common but serious complication of the viral infection. B27.91 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other viral diseases (b25-b34).
B27.91 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Verify documentation clearly states both the infectious mononucleosis diagnosis AND the polyneuropathy complication before assigning this combination code.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B27.91 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify documentation clearly states both the infectious mononucleosis diagnosis AND the polyneuropathy complication before assigning this combination code
- •Do not use this code if the polyneuropathy is unrelated to the mononucleosis; instead, code them separately with appropriate linkage documentation