Parvovirus B19 in patients with haemolytic anaemias: Risk of aplastic crisis

Red blood cells contain haemoglobin which carries oxygen around the body. They are constantly being made in the bone marrow and then destroyed as they get old. In haemolytic anaemias (HA) the red blood cells are destroyed more rapidly than normal. This means that the bone marrow has to make them at a faster rate to compensate.

Some haemolytic anaemias are genetic which means that you are born with them. These include sickle cell disorder, thalassaemia, hereditary spherocytosis and pyruvate kinase deficiency. Others, such as autoimmune haemolytic anaemia, are acquired. This means that you can develop them at any time in your life.

Haemolytic anaemias can lead to various health problems. These include gallstones (small stones that develop in the gallbladder) and fatigue.

Parvovirus B19 is a virus which causes an illness sometimes known as ‘slapped cheek’, ‘fifth disease’ or ‘erythema infectiosum’. It spreads through saliva, nasal mucus or sputum (mixture of saliva and mucus) when an infected person coughs or sneezes.

The first sign of parvovirus B19 is usually feeling unwell for a few days. Symptoms may include:

• a high temperature of 38°C or more
• a runny nose and sore throat
• a headache
• a classical rash on the face described as ‘slapped cheek’. Please note that this is not always present, or may not be visible if you have darker skin.

Parvovirus switches off the red blood cell production in the bone marrow for about a week. This is called red cell aplasia.

The red blood cells in people without haemolytic anaemia live for around 120 days. This means that an infection with parvovirus will only slightly reduce their number in the blood. Even though some of the red blood cells will be destroyed during red cell aplasia and not replaced, most of them will survive. This may cause mild anaemia, symptoms of which include tiredness and faster pulse and breathing.

If you have a haemolytic anaemia, the lifespan of your red blood cells is already reduced. If you don’t make red blood cells for a week or so, their number can become dangerously low causing severe anaemia. This is known as an aplastic crisis. Severe anaemia can make you extremely lethargic, breathless and unwell. Very rarely, severe anaemia, for example due to parvovirus, can cause death.

If you think you are at risk of getting parvovirus, for example there is an outbreak of parvovirus at school but your child hasn’t got any symptoms yet, call your clinical nurse specialist (CNS). She/he will most likely make an appointment to see you and arrange for a blood test.

If you have symptoms of severe anaemia, such as feeling lethargic and breathless, looking pale or feeling like your heart is racing, come to the Emergency Department (A&E) at UCLH. Contact your haematology team so that they can prepare for your arrival and let the on-call team know a bit more about you.

It’s important that you seek advice from your healthcare team if you are worried or unsure about your symptoms.

Your doctor might suspect parvovirus if:

• you have a low reticulocyte count (reticulocytes are very young red blood cells)
• your anaemia is more severe than usual
• you have some of the viral symptoms listed earlier on this page.

As with many viruses, such as chickenpox, most people have parvovirus in childhood and then form immunity (resistance) to it. This means that if they are in contact with the infection again, their immune system will combat it.

You can have a blood test to check if you are immune to parvovirus.

If you are more anaemic than usual or you are struggling with your anaemia, you may need a blood transfusion. We may also monitor your blood count until the bone marrow recovers. We can tell that the bone marrow has recovered when there is an increase of reticulocytes in your blood.

People with deficient immune systems often need antibody treatment known as immunoglobulin. Deficient immune system is when the immune system is compromised or unable to fight infections. However, this is rarely the case in haemolytic anaemias.

People with deficient immune systems may develop chronic red cell aplasia. This is red cell aplasia that persists for months. Pregnant women may also pass the infection on to their unborn baby. This can cause them to be severely anaemic and is known as foetal hydrops.

If you had a blood transfusion, this should bring your haemoglobin level up. The haemoglobin usually increases 15g/l per week in people with haemolytic anaemias, provided they are young and healthy. As your bone marrow recovers and your haemoglobin level increases, you will start to feel more like yourself and your energy will be up too.

If you don’t already take it, you may be prescribed folic acid to take every day during recovery. You may also have another blood test to check your blood count.

You can find out more about parvovirus on the NHS website, but most of this is relevant to people who don’t have a haemolytic anaemia.

University College London Hospitals NHS Foundation Trust cannot accept responsibility for information provided by external organisations.