Alpha chain hemoglobins with electrophoretic mobility similar to that of hemoglobin S in a newborn screening program.

OBJECTIVE: To characterize alpha-chain variant hemoglobins with electric mobility similar to that of hemoglobin S in a newborn screening program. METHODS: ß(S) allele and alpha-thalassemia deletions were investigated in 14 children who had undefined hemoglobin at birth and an electrophoretic profile similar to that of hemoglobin S when they were six months old. Gene sequencing and restriction enzymes (DdeI, BsaJI, NlaIV, Bsu36I and TaqI) were used to identify hemoglobins. Clinical and hematological data were obtained from children who attended scheduled medical visits. RESULTS: THE FOLLOWING ALPHA CHAIN VARIANTS WERE FOUND: seven children with hemoglobin Hasharon [alpha2 47(CE5) Asp>His, HbA2:c.142G>C], all associated with alpha-thalassemia, five with hemoglobin Ottawa [alpha1 15(A13) Gly>Arg, HBA1:c.46G>C], one with hemoglobin St Luke's [alpha1 95(G2) Pro>Arg, HBA1:c.287C>G] and another one with hemoglobin Etobicoke [alpha212 84(F5) Ser>Arg, HBA212:c.255C>G]. Two associations with hemoglobin S were found: one with hemoglobin Ottawa and one with hemoglobin St Luke's. The mutation underlying hemoglobin Etobicoke was located in a hybrid α212 allele in one child. There was no evidence of clinically relevant hemoglobins detected in this study. CONCLUSION: Apparently these are the first cases of hemoglobin Ottawa, St Luke's, Etobicoke and the α212 gene described in Brazil. The hemoglobins detected in this study may lead to false diagnosis of sickle cell trait or sickle cell disease when only isoelectric focusing is used in neonatal screening. Additional tests are necessary for the correct identification of hemoglobin variants.

Alpha chain hemoglobins with electrophoretic mobility similar to that of hemoglobin S in a newborn screening program

OBJECTIVE: To characterize alpha-chain variant hemoglobins with electric mobility similar to that of hemoglobin S in a newborn screening program. METHODS: βS allele and alpha-thalassemia deletions were investigated in 14 children who had undefined hemoglobin at birth and an electrophoretic profile similar to that of hemoglobin S when they were six months old. Gene sequencing and restriction enzymes (DdeI, BsaJI, NlaIV, Bsu36I and TaqI) were used to identify hemoglobins. Clinical and hematological data were obtained from children who attended scheduled medical visits. RESULTS: The following alpha chain variants were found: seven children with hemoglobin Hasharon [alpha2 47(CE5) Asp>His, HbA2:c.142G>C], all associated with alpha-thalassemia, five with hemoglobin Ottawa [alpha1 15(A13) Gly>Arg, HBA1:c.46G>C], one with hemoglobin St Luke's [alpha1 95(G2) Pro>Arg, HBA1:c.287C>G] and another one with hemoglobin Etobicoke [alpha212 84(F5) Ser>Arg, HBA212:c.255C>G]. Two associations with hemoglobin S were found: one with hemoglobin Ottawa and one with hemoglobin St Luke's. The mutation underlying hemoglobin Etobicoke was located in a hybrid α212 allele in one child. There was no evidence of clinically relevant hemoglobins detected in this study. CONCLUSION: Apparently these are the first cases of hemoglobin Ottawa, St Luke's, Etobicoke and the α212 gene described in Brazil. The hemoglobins detected in this study may lead to false diagnosis of sickle cell trait or sickle cell disease when only isoelectric focusing is used in neonatal screening. Additional tests are necessary for the correct identification of hemoglobin variants.

Hb Stanleyville-II [α78(EF7)Asn→Lys (α2); HbA2: c.237C>A]: incidence of 1:11,500 in a newborn screening program in Brazil.

Almost 3 million babies were tested in a newborn screening program in Minas Gerais, Brazil (1998-2008); 128 who have S-like hemoglobins (Hbs) were tested for the ß(S) allele and 112 were identified through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or sequencing. Hb Stanleyville-II [α78(EF7)Asn→Lys (α2); HbA2: c.237C>A] was present in 96 children (85.7%), two in a homozygous state and 94 in a heterozygous state. Its estimated prevalence was 1:11,500. Hbs Hasharon [α47(CE5)Asp→His, GAC>CAC (α2)], Ottawa [α15(A13)Gly→Arg (GGT>CGT) (α2 or α1)], G-Ferrara [ß57(E1)Asn→Lys (AAC>AAA or AAG)], St. Luke's [α95(G2)Pro→Arg, C CG>C GG (α1)], Maputo [ß47(CD6)Asp→Tyr (GAT>TAT)] and Etobicoke [α84(F5)Ser→Arg (AG C>AG G or CGC or AGA) (α2 or α1)] were also identified. Many children with Hbs Stanleyville-II and Hasharon also co-inherited the -α(3.7) thalassemia gene. African ancestry was recognized by parents of all 31 children with Hb Stanleyville-II who were interviewed. Mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) values were significantly lower in children with α-thalassemia (α-thal). We came to the conclusion that Hb Stanleyville-II is not so uncommon in Brazil and seems to have originated from the African slave trade. This study reinforces the importance of an accurate diagnosis of variants that have electrophoretic mobility similar to Hb S [ß6(A3)Glu→Val, GAG>GTG] so that false diagnoses are avoided.

Unstable hemoglobin Rush [beta 101(G3) Glu>Gln, HBB:c.304G>C] in a Brazilian family with moderate hemolytic anemia.

Hemoglobin Rush is an unstable variant generated by a mutation of the ß-globin gene which causes amino acid replacement Glu>Gln in the central cavity of hemoglobin (G3). Many members of a Brazilian family of Italian descent have hemoglobin Rush. This is the second report in world literature. Clinical and laboratory features were retrieved and gene mutation was characterized. Hemoglobin electrophoresis, gene sequencing, and restriction fragment length polymorphism with Hpy188I were used to characterize it. In 13 affected members, hemoglobin ranged from 9.3 to 13.0 g/dL and reticulocyte count up to 12.8%. The intensity of hemolysis appeared to be linked to increased stress. The mutation was proved to be HBB:c.304G>C, beta 101(G3) Glu>Gln. Heterozygous hemoglobin Rush should be suspected when alkaline electrophoresis shows three bands, whereas isoelectric focusing and acid electrophoresis show only two. Adequate genetic counseling to avoid intermarriage should be provided because homozygous hemoglobin Rush is predicted to be clinically severe.