Infectious mononucleosis Flashcards
Define infectious mononucleosis.
Clinical syndrome caused by primary EBV infection. Also known as glandular fever
What is the aetiology of IM?
- EBV is spread by saliva/respiratory droplets
- Predilection for B lymphocytes, incorporation of viral DNA into host DNA
How common is IM?
- Affects 90-95% of people at some point in their lives (seroprevalence in 35-40yr age group is 90%)
- Peaks at age 15-19yrs
- Tends to occur later in developed countries
AKA the “kissing” disease because usually spread through saliva
What is Epstein Barr virus?
Herpes simplex virus 4
How do you distinguish infectious mononucleosis from tonsillitis?
Tonsillitis -anterior cervical lymphadenopathy
IM - posterior cervical lymphadenopathy
What is the pathophysiology of glandular fever?
EBV has lytic and latent phase
Lytic - EBV infects oropharyngeal B cells via tonsillar crypts. B cells spread the infection to liver/spleen/lymph nodes → humoral response to the virus → antibodies against EBV structural proteins VCAs, EAs, EBNA. T cell response is essential for suppression of infection
Latent - self-replicating extra-chromosomal nucleic acid; EBV immortalises infected lymphocytes (in a seropositive adult 0.005% of circulating B cells will be EBV infected)
What is the triad of infectious mononucleosis?
- Pyrexia
- Pharyngitis
- Lymphadenopathy with atypical lymphocytosis
What are the signs and symptoms of IM?
- Cervical/generalised lymphadenopathy (posterior cervical)
- Pharyngitis (tonsillar exudates)
- Fever
- Splenomegaly (50%)
- Malaise, anorexia, headache
Other:
- Palatal petechiae
- Rash (10%) - erythematous, maculopapular, or morbilliform; or maculopapular pruritic rash IF AMOXICILLIN taken
- Hepatitis, transient rise in ALT
- Jaundice
Symptoms resolve after 2-4 weeks.
How do you diagnose IM?
- Classical triad of fever, pharyngitis, lymphadenopathy
- In 2nd week: FBC - atypical lymphocytosis (highest in week 2-3)
- In 2nd week: Heterophil antibody test (Monospot test) - confirms diagnosis; IgM agglutinates red cells from other species.
Other:
- Blood film - atypical lymphocytes
- heterophile antibodies - Monospot test;
- EBV-specific antibodies - positive for VCA-IgM, VCA-IgG, EA, EBV EBNA
- real-time PCR - EBV DNA detection
How do you manage infectious mononucleosis?
- Supportive care - paracetamol or ibuprofen
- Corticosteroids -e.g. prednisolone for severe cases (e.g haemolytic anaemia, severe tonsillar swelling, obstructive pharyngitis)
Amoxicillin/ampicillin CONTRAINDICATED –> maculopapular pruritic rash
What is the prognosis with IM?
Good prognosis for healthy people.
EBV infection can be asymptomatic, cause mild, non-specific symptoms, or cause IM with symptoms and fatigue lasting up to 6 months or more.
How would you interpret these results?
- IgM – infection present now
- IgG – capsid antigen
- ENBA - only after the infection is gone completely
BUT this is rarely tested in practice.
What is the Paul Bunnell test?
A heterophil antibody test - sensitive but not specific for the causative EBV.
False positive results can occur with other viruses and leukaemia.
How long until return to contact sports?
3-8 weeks
What are the complications of IM?
- fatigue -may last up to 6 months or more
- severe upper airway obstruction,
- depression
- meningitis
- splenic rupture,
- fulminant hepatitis,
- encephalitis,
- severe thrombocytopenia,
- and haemolytic anaemia.