Myelodysplastic and myeloproliferative disorders
Myelodysplastic syndrome (MDS) is a premalignant condition in which there are abnormal stem cells resulting in production of abnormal cells, anaemia, neutropenia and thrombocytopenia.
20 per 100,000 per year over the age of 70 years.
More than 80% of patients are over the age of 60 years.
Myelodysplastic syndromes are classified using the WHO classification dependent on the peripheral blood and bone marrow findings into:
· Refractory anaemia (RA).
· Refractory anaemia with ringed sideroblasts (RARS).
· Refractory cytopenia with multilineage dysplasia(RCMD).
· Refractory cytopenia with multilineage dysplasia and ringed sideroblasts (RCMD-RS).
· Refractory anaemia with excess blasts-1 (RAEB-1).
· Refractory anaemia with excess blasts-2 (RAEB-2).
· Myelodysplastic syndrome, unclassified (MDS-U).
· MDS associated with isolated deletion (5q).
The disorder arises from a single abnormal stem cell. MDS is initially indolent due to inhibitory cytokines, however over time oncogenes are activated and tumour suppressor genes inactivated resulting in a proproliferative aggressive condition which may progress to acute myeloid leukaemia. Dysplastic stem cells are refractory to haemopoetic growth factors resulting in a peripheral cytopenia.
Patients with myelodysplastic syndrome typically present with symptoms of anaemia, thrombocytopenia (spontaneous bruising and petechiae or mucosal bleeding) or leucopenia (recurrent infections of the skin, mucosal surfaces or lungs).
Bone marrow aspirate examination shows normal or increased cellularity with megaloblastic cells and sometimes ring sideroblasts and abnormal myeloblasts.
Supportive therapy includes red blood cell and platelet transfusions and the use of antibiotics for infections. Allogeneic stem cell transplantation is potentially curative but is only used in the rare cases arising in young patients. In older patients chemotherapy may be used especially in the more aggressive forms of MDS. Patients with less aggressive forms of MDS may benefit from the use of haemopoetic growth factors.