Infectious mononucleosis (B27) ICD-10-CM
The B27 code range covers infectious mononucleosis with 21 ICD-10-CM diagnosis codes. 16 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- glandular fever
- monocytic angina
- Pfeiffer's disease
Codes in the B27 Range 21 codes · 16 billable
- B27 Infectious mononucleosisNon-billable
- B27.0 Gammaherpesviral mononucleosisNon-billable
- B27.00 Gammaherpesviral mononucleosis without complication
- B27.01 Gammaherpesviral mononucleosis with polyneuropathy
- B27.02 Gammaherpesviral mononucleosis with meningitis
- B27.09 Gammaherpesviral mononucleosis with other complications
- B27.1 Cytomegaloviral mononucleosisNon-billable
- B27.10 Cytomegaloviral mononucleosis without complications
- B27.11 Cytomegaloviral mononucleosis with polyneuropathy
- B27.12 Cytomegaloviral mononucleosis with meningitis
- B27.19 Cytomegaloviral mononucleosis with other complication
- B27.8 Other infectious mononucleosisNon-billable
- B27.80 Other infectious mononucleosis without complication
- B27.81 Other infectious mononucleosis with polyneuropathy
- B27.82 Other infectious mononucleosis with meningitis
- B27.89 Other infectious mononucleosis with other complication
- B27.9 Infectious mononucleosis, unspecifiedNon-billable
- B27.90 Infectious mononucleosis, unspecified without complication
- B27.91 Infectious mononucleosis, unspecified with polyneuropathy
- B27.92 Infectious mononucleosis, unspecified with meningitis
- B27.99 Infectious mononucleosis, unspecified with other complication
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the B27 range.
Fatigue Syndrome, Chronic
A syndrome characterized by persistent or recurrent fatigue, diffuse musculoskeletal pain, sleep disturbances, and subjective cognitive impairment of 6 months duration or longer. Symptoms are not caused by ongoing exertion; are not relieved by rest; and result in a substantial reduction of previous levels of occupational, educational, social, or personal activities. Minor alterations of immune, neuroendocrine, and autonomic function may be associated with this syndrome. There is also considerable overlap between this condition and FIBROMYALGIA. (From Semin Neurol 1998;18(2):237-42; Ann Intern Med 1994 Dec 15;121(12): 953-9)
Fibromyalgia
A common nonarticular rheumatic syndrome characterized by myalgia and multiple points of focal muscle tenderness to palpation (trigger points). Muscle pain is typically aggravated by inactivity or exposure to cold. This condition is often associated with general symptoms, such as sleep disturbances, fatigue, stiffness, HEADACHES, and occasionally DEPRESSION. There is significant overlap between fibromyalgia and the chronic fatigue syndrome (FATIGUE SYNDROME, CHRONIC). Fibromyalgia may arise as a primary or secondary disease process. It is most frequent in females aged 20 to 50 years. (From Adams et al., Principles of Neurology, 6th ed, p1494-95)
Herpesvirus 4, Human
The type species of LYMPHOCRYPTOVIRUS, subfamily GAMMAHERPESVIRINAE, infecting B-cells in humans. It is thought to be the causative agent of INFECTIOUS MONONUCLEOSIS and is strongly associated with oral hairy leukoplakia (LEUKOPLAKIA, HAIRY;), BURKITT LYMPHOMA; and other malignancies.
Infectious Mononucleosis
A common, acute infection usually caused by the Epstein-Barr virus (HERPESVIRUS 4, HUMAN). There is an increase in mononuclear white blood cells and other atypical lymphocytes, generalized lymphadenopathy, splenomegaly, and occasionally hepatomegaly with hepatitis.
About the B27 Code Range
ICD-10 code B27 covers infectious mononucleosis, a viral illness commonly associated with the Epstein-Barr virus (EBV). These codes classify different types and complications of infectious mononucleosis to support precise diagnosis and treatment documentation.
The section includes codes for gammaherpesviral mononucleosis (B27.0 series), often synonymous with Epstein-Barr virus infectious mononucleosis, also known as glandular fever or EBV disease. Specific subcodes distinguish cases without complications (B27.00), with polyneuropathy (B27.01), meningitis (B27.02), or other complications like encephalitis or viral pneumonia (B27.09). Additionally, cytomegaloviral mononucleosis (B27.1 series) is detailed, including instances with or without neurological or meningitis complications. Other infectious causes of mononucleosis (B27.8 series) such as those caused by HIV or Toxoplasma are also captured, as well as codes for unspecified cases (B27.9 series). These distinctions help medical coders select the exact ICD-10 code for conditions like Epstein-Barr virus infection or cytomegalovirus-related mononucleosis, ensuring accurate classification in health records.
Questions About This Page
How many billable codes are in the B27 range?
Of the 21 codes in this range, 16 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the B27 range classify?
The range classifies infectious mononucleosis. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
