alpha-thalassemia belongs to those inherited diseases in which large genomic deletions/duplications represent a significant proportion of causative mutations. Until recently, large alpha-globin gene cluster rearrangements have been mainly detected by gap-PCR and Southern blotting, methods that have significant drawbacks. We tested the recently developed multiplex ligation-dependent probe amplification (MLPA) assay for deletional screening of the alpha-globin gene cluster in a cohort of 25 individuals suspected of having alpha-globin alteration(s), in which no or doubtful mutations had been found using conventional methods. In 13 out of 18 alpha-thalassemia carriers and in all 5 patients with HbH we found the causative alpha-globin defects. In 2 thalassemia intermedia patients, carriers of heterozygous beta-globin mutations, the co-inheritance of homozygous alpha-genes triplication was detected. MLPA results were subsequently confirmed by real-time PCR. This study shows that MLPA can effectively identify different and unknown types of alpha-globin gene rearrangements, to allow characterizing previously unsolved alpha-thalassemia genotypes. (C) 2010 Elsevier Inc. All rights reserved.