The MPL mutation test may be used, along with other tests such as erythropoietin, to help diagnose bone marrow disorders that lead to overproduction of blood cells. These conditions are known as myeloproliferative neoplasms (MPNs).
The MPNs most commonly associated with MPL mutation are: polycythaemia vera (PV), in which the bone marrow makes too many red blood cells; essential thrombocythaemia (ET), in which there are too many platelet-producing cells in the bone marrow; and primary myelofibrosis (PMF), also known as chronic idiopathic myelofibrosis or agnogenic myeloid metaplasia, in which there are too many platelet-producing cells and cells that produce scar tissue in the bone marrow. The MPL mutation test is typically ordered as a follow-up test if a person has a significantly increased haemoglobin and/or platelet count and the medical practitioner suspects that the person may have an MPN.
The MPL mutation
test may be ordered along with other tests when a medical practitioner suspects that a person has a blood disorder known as a myeloproliferative neoplasm (MPN), especially polycythaemia vera (PV), essential thrombocythaemia (ET), or primary myelofibrosis (PMF). Many routine laboratory results such as a full blood count (FBC)
reveal abnormal results associated with these MPNs, and someone may also have signs
that suggest an MPN.
Sometimes people with MPNs may have no symptoms or a few, relatively mild ones that may be present for years before being recognised as an MPN, often during a routine physical examination. However, if certain signs and symptoms appear, a health care provider may suspect that someone has one of these MPNs. They have many signs and symptoms in common, for example:
- Weakness and fatigue
- Shortness of breath during exertion
- Loss of appetite and weight loss
- Enlarged spleen (splenomegaly)
- Bleeding and bruising, due to low and/or abnormal platelets
- Night sweats
- Bone and joint pain
- A pale appearance due to anaemia (when red blood cells are decreased)
- Frequent infections
Polycythaemia vera (PV) may also be suspected when symptoms such as headaches, dizziness, visual distortion, itching and paraesthesia
(abnormal skin sensation, such as tickling, tingling or numbness) appear. In PV, there are an excess number of red blood cells and the resulting blood thickening may lead to complications such as stomach ulcers, kidney stones
, venous thrombosis, stroke
and rarely to congestive heart failure
. Since PV symptoms may be slow to appear, it is often discovered during routine blood tests.
Those with essential thrombocythaemia (ET) usually have no symptoms, but some may develop inappropriate blood clots (thrombosis
) or bleeding (haemorrhage
) because there are increased numbers of platelets produced that may not function properly. A blood clot could also cause a temporary interruption of blood flow to part of the brain (a transient ischemic attack) or stroke. Other symptoms from blood clots or excessive bleeding may include tingling in the hands and feet, headaches, dizziness, nosebleeds, and easy bruising.
Primary myelofibrosis (PMF) is a serious disorder that leads to bone marrow scarring and can eventually evolve into other, more serious forms of leukaemia
. However, some people with PMF have no symptoms for years. People who do have symptoms may have those that are associated with severe anaemia, such as fatigue and weakness. A MPL
mutation test may be done if routine laboratory tests suggest PMF.
If the MPL W515L or W515K mutation is detected and the person has other supporting clinical signs, then it is likely that the person has an MPN. Other testing, such as a bone marrow biopsy, may need to be performed to determine which MPN the person has and to evaluate its severity.
If the person is negative for MPL mutations, the person may still have an MPN. The person could have mutations in other genes such as JAK2
. Mutation testing for both MPL and JAK2 are often ordered at the same time since both lead to the same symptoms.