Molecular diagnosis of haemoglobin disorders

Abstract

The haemoglobinopathies refer to a diverse group of inherited disorders characterized by a reduced synthesis of one or more globin chains (thalassaemias) or the synthesis of a structurally abnormal haemoglobin (Hb). In prevalent regions, the thalassaemias often coexist with a variety of structural Hb variants giving rise to complex genotypes and an extremely wide spectrum of clinical and haematological phenotypes. An appreciation of these phenotypes is needed to facilitate the definitive diagnosis of the causative mutations to inform management and counselling. Haematological and biochemical investigations, and family studies provide essential clues to the different interactions and are fundamental to DNA diagnostics of the Hb disorders. With the exception of a few rare deletions and rearrangements, the molecular lesions causing haemoglobinopathies are all identifiable by PCR-based techniques. Although a full spectrum of >1000 mutations causing haemoglobinopathies has been documented, in practice only a limited number are associated with disease states and clinical significance. Furthermore, each at-risk ethnic group has its own combination of common Hb variants and thalassaemia mutations. Prior identification of the ethnic origin is thus an important part of the diagnostic strategy which becomes less reliable in the UK because of the large ethnic mix. Although the current approach using a combination of different PCR-based techniques seems to work in most laboratories, practice pressures with the imminent implementation of universal antenatal screening for clinically significant Hb disorders in the UK will require a higher throughput approach for DNA diagnostics in the near future. The complex mutational spectrum and the compactness of the globin genes places them in an ideal position for the different non-gel based analytical platforms.

Ion Trap Collision-Induced Dissociation of Human Hemoglobin α-Chain Cations

“…However, there were significant differences in the relative contributions of these channels as well as differences in the identities of other contributing channels, depending upon charge state. The post ion/ion reaction product ion spectra of the [ 28 ). This cleavage eventually becomes the most dominant process at high charge states (see below) and is consistent with N-terminal proline cleavages showing some enhancement in the presence of N-terminal leucine [58].…”

“…Top-down protein tandem mass spectrometry [20 -22] is particularly attractive for rapid analysis of hemoglobin variants because it avoids digestion altogether by subjecting the intact globin chains directly to tandem mass spectrometry. Of the two globin chains in hemoglobin A, the ␤-chain has been the subject of most attention [23][24][25][26], in part because the majority of hemoglobin variants are ␤-chain variants [27,28]. However, tandem mass spectrometry of the ϩ11 to ϩ14 charge states of the intact ␣-chain of human apohemoglobin has been reported [29], with particular emphasis placed on the favored dissociation between D 75 /M 76 in the ϩ11 and ϩ12 charge states.…”

Hypercoagulability in splenectomized thalassemic patients detected by whole-blood thromboelastometry, but not by thrombin generation in platelet-poor plasma

“…1,2 From the hemostatic stand point it is characterized by hypercoagulability and an increased risk of venous and/or arterial thromboembolism. [3][4][5][6] However, not all patients with thalassemia present with the same risk and the identification of those at higher risk is not possible on the basis of the measurements of the individual components of the hemostatic system nor on the basis of global conventional coagulation tests such as the prothrombin time (PT) or the activated partial thromboplastin time (APTT).…”

Ferrocinetic patterns in beta-thalassemia minor

“…c) Los casos que se asocian a déficit en vitamina B-12 y de folato. d) Hay casos raros de beta talasemia minor con hemoglobina A2 normal (10).…”