Infectious mononucleosis

Question 1

What is IM?

Answer 1

Infectious mononucleosis (IM) is a condition caused by infection with the Epstein Barr virus (EBV). It is commonly known as the “kissing disease”, “glandular fever” or “mono”. This virus is found in the saliva of infected individuals. Infection may be spread by kissing or by sharing cups, toothbrushes and other equipment that transmits saliva.

Question 2

Features of mono?

Answer 2

Fever
Sore throat
Fatigue
Lymphadenopathy (swollen lymph nodes)
Tonsillar enlargement
Splenomegaly and in rare cases splenic rupture

TOM TIP: Look out for the exam question that describes an adolescent with a sore throat, who develops an itchy rash after taking amoxicillin. Mononucleosis causes an intensely itchy maculopapular rash in response to amoxicillin or cefalosporins.

Question 3

Diagnosis mono?

Answer 3

In infectious mononucleosis, the body produces something called heterophile antibodies, which are antibodies that are more multipurpose and not specific to the EBV antigens. It takes up to 6 weeks for these antibodies to be produced.

We can test for these heterophile antibodies using two tests:

Monospot test: this introduces the patient’s blood to red blood cells from horses. Heterophile antibodies (if present) will react to the horse red blood cells and give a positive result.

Paul-Bunnell test: this is similar to the monospot test but uses red blood cells from sheep.

These tests are almost 100% specific for infectious mononucleosis, however not everyone who has IM produces heterophile antibodies, and it can take up to six weeks for the antibodies to be produced. Therefore they are only 70 – 80% sensitive.

Specific Antibody Tests

It is possible to test for specific EBV antibodies. These antibodies target something called viral capsid antigen (VCA):

The IgM antibody rises early and suggests acute infection
The IgG antibody persists after the condition and suggests immunity

Question 4

Management and prognosis of mono?

Answer 4

Infectious mononucleosis is usually self limiting. The acute illness lasts around 2 – 3 weeks, however it can leave the patient with fatigue for several months once the infection is cleared.

Patients are advised to avoid alcohol, as EBV impacts the ability of the liver to process the alcohol. Patients are advised to avoid contact sports due to the risk of splenic rupture. Emergency surgery is usually required if splenic rupture occurs.

Question 5

Complications mono?

Answer 5

Splenic rupture
Glomerulonephritis
Haemolytic anaemia
Thrombocytopenia
Chronic fatigue

EBV infection is associated with certain cancers, notable Burkitt’s lymphoma.