Possible complications

Possible complications of PV 

The most serious symptom of PV involves vascular occlusions caused by blood clots and their consequences, which are known as thromboembolic events.

Here the surrounding tissue is no longer supplied with  sufficient oxygen and may die. If this affects large vessels, it can lead to organ failure. A brief blockage of small blood vessels in the brain can cause the blood supply to be temporarily disrupted over a limited area (TIA, transitory ischaemic attack). 

Depending on the region of the brain affected, this can manifest itself as a short period of dizziness, disordered speech, confusion, impaired vision, an unsteady gait, or an absence of sensation in certain parts of the body. TIAs are also known as mini-strokes as they cause similar symptoms. However, unlike a stroke, such symptoms quickly recede in a matter of hours (at the latest after 24 hours) and disappear again completely. TIAs should nonetheless be taken seriously as they are early warning signs of a stroke and require appropriate treatment. So don’t run any risk here and tell your doctor about all symptoms, even if they don’t last very long.

Fast action saves lives

Serious and potentially life-threatening complications of PV are the blockage of large blood vessels, possibly affecting arteries (with oxygen-rich blood) or veins (with oxygen-poor blood). An arterial occlusion in the heart can result in a heart attack and in the brain in a stroke. If a blood clot moves into the lung and blocks a pulmonary artery, the consequence is a pulmonary embolism. This will generally take the form of breathlessness and chest pain, possibly leading to circulatory failure. At all events fast action is necessary here.
Blockage of a vein deep inside in the leg is called deep vein thrombosis (DVT). It can take the form of painful swelling, reddish discolouration of the skin and a sensation of warmth in the leg. If the clot breaks free and moves into the lung, there is the risk of pulmonary embolism. Thrombosis can also occur in the large abdominal veins (porta, splenic vein, hepatic veins). 

One very rare complication is an increased tendency to bleed. It sometimes comes about when there is a huge increase in platelets (thrombocytes) that additionally coincides with a dysfunction (von Willebrand’s disease). They can no longer perform their basic function, i.e. sealing blood vessels with bleeding by clotting, possibly leading to severe internal or external bleeding.

Possible long-term effects of PV

PV should be treated as early as possible to alleviate symptoms, to avoid serious complications and to prevent the condition turning into another disease at a late stage.
In some long-term sufferers of PV alteration (transformation) of the bone marrow will occur. The blood-producing cells are partially replaced by connective tissue cells, so reducing blood formation. This is known as secondary myelofibrosis or post-PV myelofibrosis. It initially improves blood levels, which are too high, but in the long term the blood supply may no longer be sufficient, so leading to anaemia. It is not just bone marrow that can produce blood cells, but also the spleen and liver. There is increased formation of blood in these organs, causing them to enlarge.

Very rarely, PV can turn into acute myeloid leukaemia (AML) in a late stage of the disease. This is caused by a further degeneration of the blood-producing cells in the bone marrow. It stops the blood cells from maturing, so preventing them from functioning. 

This often coincides with a significant increase in altered white blood cells (leukocytes). AML is a malignant disease that progresses rapidly without treatment and may prove fatal within a short period of time, largely due to bleeding or an inability to keep infections in check (failing immune system). However, if patients receive comprehensive treatment without delay, there is a chance of complete recovery.