ABC of clinical haematology: The myelodysplastic syndromes

Introduction

The term myelodysplastic syndromes was introduced in 1975 by a group of French, American, and British haematologists (FAB group) to describe a group of disorders with characteristic abnormalities of peripheral blood and bone marrow morphology and impaired bone marrow function, which tend to evolve into acute myeloid leukaemia. Although the myelodysplastic syndromes may occur at any age, they are predominantly diseases of elderly people.

Aetiology

Primary myelodysplastic syndrome describes those cases–the majority–in which the cause is unknown. Case-control studies have shown a modest correlation between the myelodysplastic syndromes and exposure to low doses of radiation and organic chemicals.

Therapy related myelodysplastic syndrome, sometimes called secondary myelodysplastic syndrome, describes cases that have arisen as a long term complication of cytotoxic chemotherapy. The risk is highest 4-10 years after treatment with alkylating agents, such as chlorambucil and cyclophosphamide.

Diagnosis

Patients present with the features of bone marrow failure–namely, symptoms of anaemia, bacterial infections, and bleeding or bruising. Splenomegaly is present in about 10% of patients, particularly in chronic myelomonocytic leukaemia, one subtype of the myelodysplastic syndromes. Increasingly, myelodysplastic syndrome is an incidental finding in elderly patients whose routine blood count shows an unexplained anaemia, macrocytosis, neutropenia, monocytosis, or thrombocytopenia.

The myelodysplastic syndromes can be diagnosed only by a haematologist, primarily on the basis of characteristic full blood count indices, morphological abnormalities on the peripheral blood film, and characteristic bone marrow appearances. Although myelodysplastic syndrome may sometimes be diagnosed on the basis of a blood film alone, a bone marrow aspirate and trephine are necessary to make a confident diagnosis and to assess the severity of the disease. Marrow examination can safely be omitted only in elderly, infirm patients with mild …