12. Myelodysplastic syndromes and aplastic anaemia Flashcards
What is the definition of myelodysplastic syndrome (MDS)?
Biologically heterogenous group of acquired haematopoietic stem cell disorders (~4 per 100,000)
What is MDS characterised by?
Cytopaenia; qualitative (functional) abnormalities of erythroid; myeloid and megakaryocyte maturation; increased risk of transformation to leukaemia. Usually a disorder of the elderly. Symptoms/signs of general bone marrow failure.
Summarise what happens in MDS, leading to its symptoms:
Development of a clone of marrow stem cells with abnormal maturation resulting in: functionally defective blood cells and numerical reduction.
Over what time frame does MDS develop?
Develops over weeks and months
What are blood and bone marrow morphological features of MDS?
Pelger-Heut anomaly (bilobed neutrophils), dysgranulopoiesis of neutrophils (failure of granulation), dyserythropoiesis of red cells (lack of separation between red cell precursors, abnormal ring of cytoplasm around the nucleus), dysplastic megakaryocytes (e.g. micro-megakaryocytes), increased proportion of blast cells in the marrow (normally <5%), ringed sideroblasts, myeloblasts with Auer rods.
What are ringed sideroblasts?
If you stain the bone marrow for iron you may see iron granules within the red cell precursors. These are ringed sideroblasts (an accumulation of iron around the nucleus).
What do blast cells with Auer rods look like?
Blast cells have a big nucleus with nucleoli. Rod-like structure in cytoplasm is called an Auer rod. These are a feature of acute myeloid leukaemia.
What is taken into account when classifying MDS?
WHO classification of MDS (2018). Different things are taken into account when classifying MDS (e.g. lineages, blast cell proportions, cytogenetics, presence of ringed sideroblasts
What is used to find out the prognosis of MDS?
Revised International Prognostic Scoring System (PSS-R) in MDS (2012)
What prognostic variables does the Revised International Prognostic Scoring System include?
BM blasts, karyotype, Hb, platelets, neutrophils
What karyotypes in MDS are associated with a poor or very poor prognosis?
Poor: Complex (3 abnormalities, -7, double abnormalities inc. -7 or del(7q). Very poor: > 3 abnormalities
What is the median survival of patients with MDS according to the IPSS-R?
Very low risk category: 8.8 years. Intermediate: 3.0 years. Very high risk: 0.8 years
What is AML evolution in 25% of MDS patients (years)?
Very low risk: >14.5. Intermediate risk: 3.2. Very high risk: 0.7
Describe the evolution of myelodysplasia?
Blood cell counts will decrease as a result of BM failure. Patients may develop AML. 1/3 die from infection; 1/3 die from bleeding; 1/3 die from acute leukaemia.
What percentage of MDS patients develop AML? What is the prognosis?
Develops in 5-50% within 1 year (depending on subtype). Some cases are much slower to evolve. AML on a background of MDS has an extremely poor prognosis.
What is the treatment for MDS?
Only TWO treatments can prolong life: allogenic stem cell transplantation (SCT) and intensive chemotherapy. Other Mx: supportive care (blood product support, antimicrobial support, GFs); biological modifiers; oral chemotherapy; low-dose chemotherapy; and intensive chemotherapy/SCT (AML-type regimens)
What are the issues with MDS treatment?
Only a minority of MDS patients can benefit from them. As a lot of MDS patients are elderly, few can tolerate such aggressive treatments.
What are GFs that can be given as supportive care in MDS?
E.g. EPO, G-CSF
What are examples of biological modifiers that can be given in MDS?
Immunosuppressive agents; azacytidine (hypomethylating agent); decitabine; lenalidomide (used in 5q minus syndrome)
What are examples of oral and low-dose chemotherapies that can be given in MDS?
Oral: Hydroxyurea/hydroxycarbamide. Low-dose: Subcutaneous low-dose cytarabine
Draw out an overview of haemopoietic cell lines:
Start: multipotential haemopoietic stem cell (haemocytoblast). This dividides into common myeloid progenitor and common lymphoid progenitor. Common myeloid progenitor –> megakaryocyte, erythrocyte, mast cell, myeloblast. Megakaryocyte -> thrombocytes. Myeloblast -> basophil, neutrophil, eosinophil, monocyte. Monocyte -> macrophage. Common lymphoid progenitor –> small lymphocytes and NK cells. Small lymphocyte -> B lymphocyte and T lymphocyte. B lymphocyte -> plasma cell.
How does BM failure occur?
Results from damage or suppression of stem or progenitor cells
What happens if there is damage to pluripotent haematopoietic stem cell?
This will impair the production of ALL peripheral blood cells (but this is RARE).
What happens if there is damage to committed progenitor cells?
Results in bi- or unicytopaenias
What are causes of primary BM failure?
Fanconi’s anaemia (multipotent stem cell); Diamond-Blackfan anaemia (red cell progenitors); Kostmann’s syndrome (neutrophil progenitors); acquired: Idiopathic aplastic anaemia (multipotent stem cell).
Which cells does Fanconi’s anaemia affect?
Multipotent stem cells
Which cells does Diamond-Blackfan anaemia affect?
Red cell progenitors
Which cells does Kostmann’s syndrome affect?
Neutrophil progenitors
Which cells does acquired: idiopathic aplastic anaemia affect?
Multipotent stem cell
What are causes of secondary BM failure?
Marrow infiltration; haematological malignancies (leukaemias, lymphomas, myelofibrosis); non-haematological (solid tumours spreading to bone marrow); radiation; drugs; chemicals (e.g. benzene); autoimmune; infection (parvovirus, viral hepatitis)
Which predictable (dose-dependent, common) drug causes BM failure
Cytotoxic drugs
Which idiosyncratic (NOT dose-dependent, rare) drugs cause BM failure?
Phenylbutazone, gold salts