What is agnogenic myeloid metaplasia (AMM)?
Agnogenic myeloid metaplasia is a progressive, chronic disease in which the bone marrow is replaced by fibrous tissue and blood is made in organs such as the liver and the spleen, instead of in the bone marrow.
This disease is marked by an enlarged spleen and progressive anemia. Agnogenic myeloid metaplasia is also called, AMM, chronic idiopathic myelofibrosis, idiopathic myelofibrosis, myelosclerosis with myeloid metaplasia, and primary myelofibrosis.
How common is agnogenic myeloid metaplasia (AMM)?
Agnogenic myeloid metaplasia (AMM) can affect patients at any age. It is considered a rare chronic disorder diagnosed in an estimated 1 per 100,000 populations. It can be managed by reducing your risk factors. Please discuss with your doctor for further information.
What are the symptoms of agnogenic myeloid metaplasia (AMM)?
What causes agnogenic myeloid metaplasia (AMM)?
Under normal conditions, the bone marrow provides a fine network of fibres on which the stem cells can divide and grow. Specialised cells in the bone marrow known as fibroblasts make these fibres.
In primary myelofibrosis, chemicals released by high numbers of platelets and abnormal megakaryocytes (platelet forming cells) over-stimulate the fibroblasts. This results in the overgrowth of thick coarse fibres in the bone marrow, which gradually replace normal bone marrow tissue. Over time this destroys the normal bone marrow environment, preventing the production of adequate numbers of red cells, white cells and platelets. This results in anaemia, low platelet counts and the production of blood cells in areas outside the bone marrow for example in the spleen and liver, which become enlarged as a result.
The exact cause of this condition remains largely unknown. However, there are some few risk factors that you can look out for.
What increases my risk for agnogenic myeloid metaplasia (AMM)?
Previously diagnosed with (post-polycythaemic myelofibrosis) or essential thrombocythaemia (post-ET myelofibrosis).
How is agnogenic myeloid metaplasia (AMM) diagnosed?
AMM is diagnosed using a combination of a physical examination showing the presence of an enlarged spleen, blood tests and a bone marrow examination. AMM is only diagnosed when other causes of marrow fibrosis (including leukaemia, lymphoma, other types of cancer that have spread to the bone marrow) have been ruled out.
People with AMM commonly present with varying degrees of anaemia. When examined under the microscope the red cells are often described as being 'teardrop-shaped'. Higher than normal numbers of white cells and platelets may be found in the early stages of this disorder, but low white cell and platelet counts are common in more advanced disease.
It is frequently impossible to obtain any samples of bone marrow fluid using a needle and syringe (bone marrow aspiration) due to marrow fibrosis. This is known as a 'dry tap'. The bone marrow trephine biopsy typically shows abnormal fibrosis of the marrow cavity.
Cytogenetic and molecular analysis of blood and bone marrow cells is also carried out to help confirm the diagnosis and may help with prognosis. A mutation in JAK2 is found in about 50% of people with primary myelofibrosis. It is unclear at present why some patients with mutations in JAK2 develop myelofibrosis and others don't.
How is agnogenic myeloid metaplasia (AMM) treated?
Some people have no symptoms when they are first diagnosed with primary myelofibrosis and do not require treatment straight away, apart from regular check-ups with their doctor to carefully monitor their disease.
For others treatment is largely supportive and is aimed at preventing complications due to low blood counts and an enlarged spleen (splenomegaly). This involves making every effort to improve your quality of life, by relieving any symptoms of anaemia or an enlarged spleen, and preventing and treating any complications that might arise from your disease or its treatment. This may include periodic blood transfusions and taking antibiotics to prevent and treat any infections.
A chemotherapy drug such as hydroxyurea, or low-doses of a drug called thalidomide may be used to reduce an enlarged spleen. In some cases, the surgical removal of the spleen (splenectomy) may be considered, especially when your spleen has enlarged so much that it is causing severe symptoms. A splenectomy may also be considered if you have an increased need for blood transfusions. This sometimes happens because the spleen is destroying blood cells, particularly platelets, at a very fast rate. Small doses of radiation to the spleen can also be given to reduce its size. This usually provides temporary relief for about 3 to 6 months.
Some younger patients who have a suitably matched donor may be offered an allogeneic (donor) stem cell transplant. This is a medical procedure that offers the only chance of cure for patients with myelofibrosis. It involves the use of very high doses of chemotherapy, with or without radiotherapy, followed by infusion of blood stem cells, which have been donated by a suitably matched donor. Stem cell transplants carry significant risks and are only suitable for a small minority of younger patients (usually under 60 years of age).
What are some lifestyle changes or home remedies that can help me manage agnogenic myeloid metaplasia (AMM)?
Talk to a counselor, therapist or oncology social worker if you need help dealing with the emotional challenges of this disease.