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 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)

Question 7

What is the triad of infectious mononucleosis?

Answer 7

• Pyrexia
• Pharyngitis
• Lymphadenopathy with atypical lymphocytosis

Question 8

What are the signs and symptoms of IM?

Answer 8

• 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.

Question 9

How do you diagnose IM?

Answer 9

• 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

Question 10

How do you manage infectious mononucleosis?

Answer 10

• 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 11

What is the prognosis with IM?

Answer 11

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 12

How would you interpret these results?

Answer 12

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.

Question 13

What is the Paul Bunnell test?

Answer 13

A heterophil antibody test - sensitive but not specific for the causative EBV.

False positive results can occur with other viruses and leukaemia.

Question 14

How long until return to contact sports?

Answer 14

3-8 weeks

Question 15

What are the complications of IM?

Answer 15

• 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.

Question 16

What types of test is the monospot test?

Answer 16

Blood test