Edition : 2
Year : 2017
Description :
Inherited haemoglobin disorders can be divided into two main groups. The first group includes the α- and β-thalassaemias, which result from the defective synthesis of the α- or β-globin chains of adult haemoglobin A. The second group includes structural haemoglobin variants like haemoglobin S, C, and E. A variety of thalassaemia phenotypes can result from the simultaneous inheritance of two different thalassaemia mutations from each parent or the co- inheritance of thalassaemia together with structural haemoglobin variants
Transfusion-dependence is one essential factor in distinguishing the various thalassaemia phenotypes and their severity. For example, the diagnosis of β-thalassaemia major entails life- long regular transfusion requirement for survival, and the term transfusion-dependent thalassaemia (TDT) is conventionally used to describe such forms [3]. Non-transfusion-dependent thalassaemias (NTDT) is a term used to label patients who do not require such lifelong regular transfusions for survival, although they may require occasional or even frequent transfusions in certain clinical settings and for defined periods of time (Figure 1-1) [4]. It should be noted, however, that TDT and NTDT are fluid categories, based on clinical parameters, variations and advances in the clinical management, as well as other modifiers of disease, which may shift a patient from one group to another during their lives. Thus, the TDT and NTDT designations should primarily represent patients’ ‘current’ clinical status and entail the understanding that these two designations are interchangeable.
NTDT encompasses three clinically distinct forms: β-thalassaemia intermedia, haemoglobin E/β-thalassaemia (mild and moderate forms), and α-thalassaemia intermedia (haemoglobin H disease) [5]. Although patients with haemoglobin S/β-thalassaemia and haemoglobin C/β- thalassaemia may have transfusion requirements similar to those of NTDT patients, these forms have other specific characteristics and management peculiarities [6, 7], and will not be covered in these guidelines.
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