Hypothesis for generation of the unstable Hb Bucuresti (beta 42 Phe-->Leu) mutation.

INTRODUCTION: Unstable hemoglobin disorders are characterized by a congenital, mostly familial chronic hemolytic anemia with episodes of severe hemolysis during febrile illnesses. Usually, isopropanol and heat stability tests lead to the diagnosis which is confirmed by protein and gene sequencing. Generation of the mutations is still a subject of controversy. PATIENT, MATERIALS AND METHODS: We describe a 6-year-old Swiss child with congenital hemolytic anemia and a negative family history. Hemoglobin was studied by IEF, HPLC reverse phase chromatography, heat stability and isopropranol tests. DNA was sequenced in both coding and non-coding strands. RESULTS: An unstable Hb was diagnosed on the basis of positive heat stability and isopropranol tests. The TTT-->TTG mutation at codon 42 corresponding to a Phe-->Leu substitution was found on DNA sequencing. Paternity was confirmed indicating that we are dealing with a new mutation. CONCLUSION: So far, three different mutations at codon 42 of the beta-chain, and two at the corresponding position of the alpha-chain have been described, all leading to a hemolytic anemia. These mutations can either represent random phenomena occurring at an important location in the heme pocket, or may be secondary to the two highly homologous zones present in this region. These homologous zones may indicate a hot spot for point mutations created by abnormal crossing over or formation of loops, and an imperfect DNA repair process.

Severe inclusion body beta-thalassaemia with haemolysis in a patient double heterozygous for beta(0)-thalassaemia and quadruplicated alpha-globin gene arrangement of the anti-4.2 type.

We describe a new case of an association of alpha-globin gene quadruplication of the anti-4.2 type with beta(0)-thalassaemia. The patient, a young woman of mixed Brazilian-Portuguese origin, suffered from chronic haemolytic anaemia with splenomegaly. Bone marrow supravital staining with brilliant cresyl blue and electron microscopy studies showed large inclusion bodies in about 3% of erythroblasts. Upon immunofluorescent staining these inclusions reacted with a monoclonal antibody to alpha- but not to beta-globin. Analysis of alpha-globin cluster by Southern blotting showed the presence of pathologic fragments specific for the anti-4.2 alpha-globin gene quadruplication. Alpha/beta mRNA ratio was higher than in cases combining alpha-globin triplication and beta(0)-thalassaemia or in cases of beta(0)-thalassaemia heterozygous state alone (18, 14.7 and 10.1 respectively). Our data confirmed the hypothesis that the clinically detectable haemolysis in this beta(0)-thalassaemic patient was due to an unusually high amount of precipitated alpha-globin in erythroid precursors. This considerable excess of alpha-globin chains was due partly to the beta-globin deficit caused by the presence of the beta(0)-thalassaemic gene, but also to the presence of 6 active alpha-globin genes resulting from alpha-globin gene quadruplication in one chromosome.

Hb Iraq-Halabja beta10 (A7) Ala-->Val (GCC-->GTC): a new beta-chain silent variant in a family with multiple Hb disorders.

A patient originating from Iraq was referred to our laboratory upon suspicion of a hemoglobinopathy. Routine hematological tests revealed a microcytic and slightly anemic phenotype with an elevated HbA2 suggestive of beta-thalassemia. Samples were obtained for several members of the family which upon examination revealed highly heterogeneous phenotypes that prompted us to investigate the case further. Sequencing of the beta-globin gene and alpha cluster mapping in the propositus and his brother showed a previously undescribed beta-globin variant:Hb Iraq-Halabja, beta10(A7) Ala-->Val (GCC-->GTC), associated with beta0-thalassemia IVS-2 nt1 G-->A and either alpha-thal-2-3.7 kb deletion (brother), or alpha-globin gene triplication anti-3.7 kb type (propositus). Detailed functional studies of the variant gave a normal oxygenation curve, a normal heterotopic action of 2,3 DPG, and normal heat stability and isopropanol precipitation tests. The variant shows a clear difference in migration properties compared to normal beta-chain only when run on PAGE urea Triton. As expected, alpha/beta-globin mRNA ratios were influenced by the concomitant presence of an alpha-globin gene pathology and the beta0 thalassemia and not by the presence of the beta-globin variant which apparently is clinically silent.

Iron overload in patients with sideroblastic anaemia is not related to the presence of the haemochromatosis Cys282Tyr and His63Asp mutations.

Forty Caucasian patients with primary acquired sideroblastic anaemia (SA), were investigated for the presence of the Cys282Tyr and/or His63Asp mutation as possible cofactor(s) for iron overload. One patient was heterozygous for the Cys282Tyr mutation and 13 heterozygotes and one homozygote for the His63Asp mutation were found (no difference compared with controls). SA patients with normal codon 63 had a mean ferritin level of 923+/-815 microg/l whereas those with codon 63 mutation had 769+/-577 microg/l (P=0.64). We conclude that ineffective erythropoiesis with no associated mutation in the HFE gene can lead to iron overload in SA patients.

[Long-term survival of 2 cases of hemochromatosis respectively homozygous for His63Asp and Cys282Tyr mutations]. / Suivi à long terme de deux cas d'hémochromatose homozygotes respectivement pour les mutations His63Asp et Cys282Tyr.

A 45-year-old Greek patient was found to have a moderate iron overload (ferritin 1213 micrograms/l, serum iron 21.5 mumol/l, transferrin saturation 40%). He underwent 12 phlebotomies of 450 cc over an 8-year period and ferritin was normalized (267 micrograms/l) after the seventh. Study of the HLA-H gene in leukocyte DNA showed that the patient is homozygous for the His63Asp mutation while no modification was found at position 282. This case is compared with that of a 50-year-old Swiss male presenting a severe iron overload (ferritin 7660 micrograms/l, serum iron 36.5 mumol/l, transferrin saturation 97%). Although this patient has undergone 77 phlebotomies (450 cc each time) over a 2-year period, he continues to have a high ferritin level (2200 micrograms/l). HLA-H gene analysis showed the absence of codon 63 mutation and the presence of Cys282Tyr mutation in the homozygous state. The study of these two cases indicates that penetrance of the His63Asp mutation in the homozygous state is very low as compared to Cys282Tyr and results in moderate iron accumulation, probably without organ damage. This genotype must be looked for whenever moderate iron overload is present.

Investigation of microcytosis: a comprehensive approach.

Microcytosis is a highly prevalent finding during blood examination. This study investigates the causes of microcytosis (defined as mean corpuscular volume (MCV) < 82 fl) in 466 patients referred to our laboratory for suspected hemoglobinopathy. The following data were obtained: Hb, MCV, serum iron, transferrin, ferritin, HbA2, HbF, isoelectric focusing of the Hb, gene mapping of chromosome 16 with Xba I and Bgl II and hybridization with an alpha- and a zeta-probe, inflammatory status. Results show that iron deficiency remains the first cause of microcytosis (35.2% of our patients), even in a selected population such as ours. Deletional alpha-thalassemia, probably the most frequent hemoglobinopathy throughout the world, represents the second most frequent cause of microcytosis (31.1%), followed by beta-thalassemia heterozygous state (18.9%). Of our patients, 1.3% had microcytosis due to the presence of an abnormal hemoglobin (HbC, Hb S/C, HbE). Three cases (0.6%) had other possible causes of microcytosis. Of the remaining 60 cases, 28 had an inflammatory state. Finally, 32 cases (6.9%) remain unexplained; taking into consideration the origin of these cases, their hematological parameters and their family history, we postulate that these cases are at high risk for non-deletional alpha-thalassemia.

Haemoglobin Tunis-Bizerte: a new alpha 1 globin 129 Leu-->Pro unstable variant with thalassaemic phenotype.

A Leu-->Pro substitution at position 129 of the alpha 1 globin gene was detected in three members of a Tunisian family by sequencing the whole alpha 2 and alpha 1 DNA. The mutation was verified by dot-blot allele-specific hybridization as well as by digestion of PCR and RT-PCR products with Nci I, since the alpha 1(129) T-->C mutation creates an additional recognition site for the above-mentioned enzyme. The alpha 1(129)(H12)Leu-->Pro substitution disturbs helix H resulting in alpha-thal trait most probably because the unstable alpha-globin chain variant cannot form alpha beta dimers. A search for the abnormal Hb and for the abnormal alpha globin chain by isoelectric focusing, carboxymethyl cellulose chromatography and electrospray ionization mass spectrometry was negative. In the heterozygous state, the alpha 1(129)(H12) Leu-->Pro variant is manifested by microcytosis (MCV approximately 73 fl), whereas in the homozygous state there is moderate anaemia with marked microcytosis (Hb 11.6 g/dl, MCV 65 fl).

Adoptive immunotherapy for recurrent CML after BMT.

Three patients with CML who relapsed after transplantation with T-depleted BM from their HLA-identical siblings were treated with transfusions of donor peripheral blood mononuclear cells, in combination with (short) IFN alpha 2 therapy. CML was successfully controlled as shown by the complete disappearance of Philadelphia-positive metaphases within 90 days of treatment. This treatment appears to be very effective as neither bcr-abl transcripts nor markers specific for hematological cells of recipient origin could be detected by very sensitive PCR techniques. Two patients treated in chronic phase are without evidence of disease 300 and 360 days after treatment. The third patient, treated in accelerated phase, died with BM aplasia, 39 days following PBMC infusions. Failure to detect residual donor-derived granulocytes, as was the case in this patient prior to initiating adoptive immunotherapy, may indicate loss of donor-derived BM activity. This may help predict and possibly prevent the occurrence of life-threatening aplasia after successful clearance of malignant hematopoiesis.

De novo initiation codon mutation (ATG-->ACG) of the beta-globin gene causing beta-thalassemia in a Swiss family.

Investigation of microcytic anemia with normal ferrous status in two members (father and daughter) of a Swiss family originating from Bern revealed high levels of HbA2 (4%, 7.3%) and HbF (3.2%, 3.1%). Direct sequence analysis of asymmetrically amplified DNA showed the ATG-->ACG mutation in the intiation codon of the beta-globin gene. Heterozygous beta-thalassemia was not found in either of the propositus's parents or in any of his brothers and sisters. Extended restriction fragment length polymorphism haplotyping of the beta chromosomes led us to the conclusion of a recent spontaneous mutation in the paternal germ cell. The results of routine HLA and blood group testing supported the stated paternity. We also found that the intragenic sequence polymorphisms (frameworks) are not always in linkage disequilibrium with the Bam HI polymorphism downstream from the beta-globin gene as previously observed. This is the second family found to carry this initiation codon mutation in the beta-globin gene. Unlike the first reported family, of Yugoslavian origin, our patients have high HbF levels and this in the absence of a C-->T substitution at -158 site 5' to G gamma.

Interaction of heterozygous beta (0)-thalassemia and triplicated alpha globin loci in a Swiss-Spanish family.

We report a Swiss-Spanish family three members of which have the clinical picture of thalassemia intermedia. Restriction endonuclease mapping of the alpha-globin cluster and digestion with Mae I of the in vitro amplified 5' segment of the beta-globin gene shows a combination of triplicated alpha globin locus, anti-3.7 kb type, with heterozygous codon 39 C----T beta (0) thalassemic mutation. These, as well as 16 similar cases reported in the literature, permit the following conclusion: a single extra alpha-globin gene gives rise to a clinically significant degree of dyserythropoietic anemia only when it interacts with a severe beta(+) or beta(0) thalassemic mutation.

Prenatal diagnosis of thalassemia and hemoglobinopathies in Switzerland.

During a 10-month period, 10 couples originating from Africa (3), the tropics (1) and the thalassemia-belt region (6), living in Switzerland, requested prenatal diagnosis of hemoglobinopathies. Hb SS (twice), Hb Bart's (Hydrops fetalis) and beta-thalassemia major were diagnosed either by gene mapping or by direct detection of the mutations in DNA amplified by the PCR procedure. Whenever it was possible to obtain fetal blood or tissue, diagnosis was confirmed. In one Vietnamese man, concomitant existence of alpha-thal 1 with beta-thalassemia resulted in an unusually high Hb level because of balanced alpha and beta globin synthesis. The 10 couples examined originated from 7 different countries and presented at least 7 different Hb pathologies. This variety of pathologies represents the main difficulty for prenatal diagnosis of hemoglobinopathies in a non-endemic country. A diagnostic approach to overcome this problem is developed.

Concomitant inheritance of homozygous alpha-thalassemia-2 with homozygous IVS-I-5 G-C beta gene mutation does not influence the severity of the thalassemic phenotype.

An Asian Indian child presented the severe transfusion dependent form of beta-thalassemia major. Sequencing data and gene mapping analysis revealed the concomitant presence of homozygous alpha-thal-2 type 3.7 kb deletion with homozygous beta+ thal IVS-1-5 G-C mutation. Further studies at the DNA level demonstrated that he was XmnI negative at the -158 G gamma site and had the haplotype + ----- +. These results indicate that in the absence of high HbF determinants, concomitant inheritance of homozygous alpha-thal-2 with homozygous severe beta+ thal does not influence the severity of the thalassemic phenotype.