Infectious mononucleosis

Question 1

Define infectious mononucleosis.

Answer 1

Clinical syndrome caused by primary EBV infection. Also known as glandular fever

Question 2

What is the aetiology of IM?

Answer 2

• EBV is spread by saliva/respiratory droplets
• Predilection for B lymphocytes, incorporation of viral DNA into host DNA

Question 3

How common is IM?

Answer 3

• 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

Question 4

What is Epstein Barr virus?

Answer 4

Herpes simplex virus 4

Question 5

How do you distinguish infectious mononucleosis from tonsillitis?

Answer 5

Tonsillitis -anterior cervical lymphadenopathy

IM - posterior cervical lymphadenopathy

Question 6

What is the pathophysiology of glandular fever?

Answer 6

EBV has lytic and latent phase

Lytic - EBV infects oropharyngeal B cells via tonsllar 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)

Question 7

What is the triad of infectious mononucleosis?

Answer 7

• Fever
• Pharyngitis
• Lymphadenopathy with atypical lymphocytosis

Question 8

What are the signs and symptoms of IM?

Answer 8

• Cervical/generalised lymphadenopathy (posterior cervical)
• Splenomegaly
• Pharyngitis (tonsillar exudates)
• Fever
• Malaise

Other:

• Rash (10%)
• Jaundice

Question 9

What investigations would you do for IM?

Answer 9

• FBC - lymphocytosis (highest in week 2-3)
• Blood film - atypical lymphocytes
• heterophile antibodies - Monospot test; IgM agglutinates red cells from other species.
• EBV-specific antibodies - positive for VCA-IgM, VCA-IgG, EA, EBV EBNA
• real-time PCR - EBV DNA detection

Question 10

How do you diagnose IM?

Answer 10

Positive heterophile antibody test and serological test for antibodies against EBV

Question 11

How do you manage infectious mononucleosis?

Answer 11

• 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

Question 12

What is the prognosis? What are the complications of infectious mononucleosis?

Answer 12

Complications:

severe upper airway obstruction, splenic rupture, fulminant hepatitis, encephalitis, severe thrombocytopenia, and haemolytic anaemia.

Prognosis:

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.

Question 13

How would you interpret these results?

Answer 13

1. IgM – infection present now
2. IgG – capsid antigen
3. ENBA - only after the infection is gone completely

BUT this is rarely tested in practice.