Myelodysplastic syndrome (MDS)

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What is Myelodysplastic syndrome?

Myelodysplastic syndrome (MDS) describes a group of bone marrow disorders that are characterised by a defect in stem cells. The bone marrow is the tissue located in the centre of long bones in the body and is responsible for producing most of the cells in the body. Stem cells are the precursor cells that divide and grow to produce each of the particular cell lineages. Haemopoetic stem cells produce cells in the blood of three classes- white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes). In Myelodysplastic syndrome (MDS) the stem cells become mutant and are no longer able to divide effectively into each of the blood cells. The normal bone marrow gradually becomes replaced with the mutant cells and there is a fall in each of the different cells within the bloodstream. Patients with this disorder therefore typically have anaemia, neutropenia and thrombocytopenia (low platelets). The latter two can predispose to infection and bleeding. The abnormal cells in the bone marrow can also transform and cause syndromes also pose a risk of transformation to Acute Myeloid Leukaemia (AML).

Who gets Myelodysplastic syndrome?

The true incidence of Myelodysplastic syndrome (MDS) is difficult to estimate as it has only recently been regarded as a distinct class of disorders and controversies exist regarding its classification. However, MDS is now considered as common as Acute Myeloid Leukaemia (AML) and more cases are beginning to be recognised. MDS is most common in elderly patients as they are more prone to bone marrow damge but it can occur in any ae group. The overall incidence is thought to be around 0.5-4 cases per one million people per year.

Predisposing Factors

The risk of MDS increases with age where patients usually older than 50 years get the primary form (no known exposure) of the disorder. The second type of MDS is acquired following drug treatments or radiotherapy that damage the bone marrow. This type accounts for most cases under fifty years of age and arises 2-8 years following the damaging treatment. Certain genetic defects (such as Down syndrome), cigarette smoking, benzene exposure and DNA repair disorders can also increase your risk of this condition. Males are affected slightly more common than females in all age groups.

Progression

The mechanism of development of MDS is not known. The course of the disease is variable, but serious complications of bone marrow failure, and transformation into acute myeloblastic leukaemia commonly occur. Patients may also get infections (due to reduced neutrophils that normally fight diseases) and bleeding problems (due to reduced platelets). The therapy-related form of the disease is normally much worse and rapidly progresses to cause a fall in red blood cells, neutrophils and platelets within the bloodstream.

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