Making sense of MDS
MDS are rare blood disorders which prevent the bone marrow from producing enough healthy blood cells. The name comes from ‘myelo’, which relates to the bone marrow and ‘dysplasia’, which means abnormal growth or shape. MDS is also known as myelodysplasia.
There are a number of different types of MDS and they all behave differently. MDS can affect just one type of blood cell (e.g. red blood cells) or more than one. MDS varies from a mild form that may need little or no treatment for many years, to a severe type of disease that can rapidly progress to AML.
MDS is classified as a cancer and it has the potential to progress to a type of blood cancer called acute myeloid leukaemia (AML). The risk of this happening, however, is small in lower risk types of MDS and some haematologists are reluctant to describe MDS as a cancer.
Symptoms vary depending on the type of MDS, i.e. which type of blood cell is affected. In lower risk types of MDS, if symptoms are present, they are usually mild at first but can slowly worsen.
Treatments and supportive options such as blood transfusions can help to control some of the symptoms of MDS, such as fatigue.
A range of potential new treatments is currently being studied to treat the disease and its symptoms to improve quality of life (QoL) for those affected.
+ What does the bone marrow do?
The bone marrow is the spongy tissue found inside the bones. It acts as a type of factory for blood cells. It produces blood cells called stem cells or blasts. In normal circumstances, these develop into more complex types of blood cells and are then released into the blood.
There are three main types of cells, each of which plays an important role:
- red blood cells contain a substance called haemoglobin, which carries oxygen from the lungs to all of the cells in the body
- white blood cells fight infections
- platelets stop bleeding by helping blood to clot.
Once produced, the cells only live for a short time inside the body and so the bone marrow needs to keep up a continuous production process of healthy blood cells. MDS prevents this process from working normally.
+ What happens in MDS?
In people with MDS, the bone marrow is actually more active than normal but it begins to make abnormal cells that are not fully developed. These immature cells can start to build up in the bone marrow or die before they reach the bloodstream. This leads to a reduction in the amount of healthy blood cells circulating in the bloodstream.
MDS can affect just one type of blood cell, or it can affect more than one. Symptoms will depend on the type(s) of blood cells that are affected:
- Lack of red blood cells can cause anaemia, which results in less oxygen being delivered to different parts of the body and leads to fatigue and sometimes breathlessness.
- Lack of white blood cells (leukopenia or neutropenia) can increase the risk of infection
- Low levels of platelets (thrombocytopenia) can cause excessive bleeding and bruising.
Red blood cells contain iron. In some people with MDS, the body tries to absorb more iron than normal and the iron remains in the body. Also, in some people with MDS, the liver produces less hepcidin, the hormone that controls iron levels in the body. This can lead to a build-up of iron (iron overload). This problem can be made worse by repeated blood transfusions (a common supportive care option for MDS), which also contain iron.
+ Is there more than one type of MDS?
There are a number of different types of MDS. These vary depending on which type of which blood cells are affected, to what extent, and whether there have been changes to the chromosomes.
In 2016, the World Health Organization (WHO) re-classified MDS into 6 main categories. This classification is based on how the cells in the bone marrow look under the microscope.
The 6 main types are:
- MDS with single lineage dysplasia (also known as MDS with unilineage dysplasia or MDS-SLD).
- MDS with multilineage dysplasia (MDS-MLD)
- MDS with ring sideroblasts (MDS-RS)
- MDS with excess blasts (MDS-EB)
- MDS with isolated del(5q)
- MDS, unclassifiable (MDS, U)
There are a number of sub-types within these categories.
MDS is also classified according to ‘risk group’. This is based on an International Prognostic Scoring System (known as the IPSS-R) and refers to the likelihood of MDS progressing to acute myeloid leukaemia (AML).
About one third of people with higher-risk MDS will develop AML. In lower-risk MDS, about 10% of patients will develop AML
There are 5 risk groups:
- very low risk
- low risk
- intermediate risk
- high risk
- very high risk.
This classification is important as it helps to decide the best type of treatment, if any. Doctors sometimes refer to ‘low risk’ and ‘high risk’ MDS. ‘Low risk’ MDS includes the ‘very low’ and ‘low’ categories in the IPSS-R score, while ‘high risk’ covers the ‘high’ and ‘very high’ categories. There is still some discussion about how patients in the ‘intermediate’ category should be classified.
+ How many people are affected by MDS?
The incidence of MDS is approximately 4 in every 100,000 people per year.
It is more common in the older population. Estimates suggest between 75-86% of people with MDS are aged 60+. However, it can occur in younger people and even children.
There are estimated to be more than 100,000 people with MDS in the EU and US.
The overall prevalence appears to be increasing owing to an ageing population and better diagnosis.
+ Why do people get MDS?
In more than 80% of people, the cause of MDS is not known. This is called primary MDS.
In rare cases, MDS can be caused by radiotherapy or chemotherapy, or exposure to certain chemicals such as benzene. This is known as secondary or treatment-related MDS.
MDS does not normally run in families but very rarely it can be inherited. This is known as Familial MDS.
It is not possible to ‘catch’ MDS from somebody else.
Your guide to the symptoms of low risk MDS
Some people with MDS have no symptoms at all, particularly if they have a lower risk form of the disease. Sometimes MDS is only picked up after a routine blood test.
Symptoms vary depending on which blood cells have been affected, but anaemia is the most common effect of MDS.
In most cases, symptoms tend to be mild at first and then gradually worsen.
+ What are the key symptoms of low risk MDS?
- Symptoms vary depending on which type of blood cell has been affected.
- About 8 in 10 people with MDS have anaemia (a low red blood cell count). This results in less oxygen being delivered to different parts of the body and can lead to symptoms such as severe tiredness, weakness, shortness of breath and palpitations (pounding, fluttering or irregular heartbeats). It can also lead to other serious health problems, such as heart disease.
- A low white blood cell count (leukopenia or neutropenia) can reduce the body’s resistance to bacterial infection. People with MDS may be prone to repeated, long-lasting infections of the skin, sinuses, lungs and the urinary tract.
- A low platelet count (thrombocytopenia) can cause unusually long-lasting bleeding, such as nosebleeds or bleeding of the gums, or a tendency to bruise easily. Some people experience tiny pinpoint-sized red spots beneath the skin, often where clothes are tight-fitting. These are called petechiae.
- A build-up of blood cells in the bone marrow can cause bone pain.
- Iron overload can also cause problems. If left untreated, it can further reduce the number of healthy red blood cells made by the body and can damage organs like the heart and liver.
+ Living with MDS: the outlook
The outlook for people with MDS depends on the type of disease they have. People with very low or low risk disease may have few, if any, symptoms. The impact of these symptoms on quality of life (QoL) can vary depending on their severity.
Even without symptoms, everyone diagnosed with MDS should be monitored on a regular basis. Where symptoms such as fatigue or infections do occur, they should be assessed and treated appropriately.
Those with higher-risk types of MDS are more likely to go on to develop a type of leukaemia called acute myeloid leukaemia (AML). If this is the case, intensive treatment may be needed. This eBook does not cover these types of MDS.