Q: My dad, who is 67, was diagnosed with polycythaemia rubra vera (PRV) late last year.

He had gone for his regular blood test at a polyclinic and was asked to go back the following day for another test. A day later, the doctor asked for him to be admitted to hospital immediately.

Can I find out why PRV is known as a blood cancer in the United States but not in Singapore, and is it infectious? Why does my dad need to take chemo medication?

A: Polycythaemia vera (PV) or polycythaemia rubra vera (PRV) is a rare disease in which the bone marrow produces too many blood cells.

This causes patients to have higher than normal numbers of red blood cells, which leads to a high haemoglobin level. Haemoglobin is found in red blood cells.

Patients may also have increased numbers of platelets and white blood cells.

Haematologists, whether in Singapore or internationally, consider PV to be a blood cancer. Cancer is defined as an abnormal, uncontrolled growth of cells. This is a feature of PV. The cause of PV is unknown but it is not infectious.

Patients develop a gene abnormality, called the JAK2 mutation, that gives rise to their condition. This mutation is not hereditary.

Although PV is a type of cancer, the way it behaves is different from what people typically think of cancer behaviour. Typically, cancers form solid tumours, which may spread to different parts of the body. However, PV does not do this. And unlike other cancers, there is no staging for PV.

The symptoms and problems that PV patients face can be highly variable. Although some patients have significant complications, their prognosis and life expectancy are generally good with treatment.

For many others, this is a chronic long-term condition and they remain relatively well for long periods of time.

Some patients may experience symptoms related to PV, such as fatigue, itch, headaches and giddiness. For some of them, PV may lead to acute leukaemia or myelofibrosis (a condition where the bone marrow becomes scarred).

This is usually a slow progression.

Although treatment can neither cure PV nor prevent it from progressing, the disease can be fatal if left untreated, as it greatly increases the risk of blood clots. These commonly lead to strokes or heart attacks, which can be life- threatening.

Treatment is usually a two- pronged approach - lowering the haematocrit (a measure of the percentage of red blood cells in the blood) to below 45 per cent and giving aspirin to make the platelets "less sticky".

These measures have been shown to reduce the risk of developing blood clots.

The haematocrit can be reduced in various ways, including:

•Regularly removing some blood from the patient to reduce the number of blood cells. This procedure, called venesection, is similar to donating blood.

•Using medication to reduce the number of blood cells and lower the haematocrit. The options available include hydroxyurea, interferon and ruxolitinib. Ruxolitinib may be used for patients who have many side effects from hydroxyurea or do not achieve good control of the haematocrit with hydroxyurea.

In older patients or those who have had a blood clot in the past, hydroxyurea would be the preferred treatment option for controlling the haematocrit.

It is critical that patients do not smoke and, if they have conditions like diabetes mellitus, high blood pressure or high cholesterol, which increase the risk of strokes and heart attacks, they should receive treatment for these conditions too.

As this is a long-term condition, it is essential for you and your father to work with the haematologist to ensure that his condition is managed well.

Dr Grace Kam

Senior consultant, department of haematology, Singapore General Hospital