A new ß(0) frameshift mutation, HBB: c.44delT (p.Leu14ArgfsX5), identified in an Argentinean family associated with secondary genetic modifiers of ß-thalassemia.

ß-Thalassemia intermedia (ß-TI) patients present with a wide spectrum of phenotypes depending on the presence of primary, secondary, and tertiary genetic modifiers which modulate, by different mechanisms, the degree of imbalance between α and ß chains. Here we describe a new ß(0) frameshift mutation, HBB: c.44delT (p.Leu14ArgfsX5), identified in four members of a family, associated with secondary genetic modifiers in three of them. The different genotype present in this family was suspected after hematological analysis and thorough observation of blood smears highlighting their importance in the identification of ß-TI patients among members of the same family.

Lineage switch in childhood acute leukemia: an unusual event with poor outcome.

Although rarely, switches between lymphoid and myeloid lineages may occur during treatment of acute leukemias (AL). Correct diagnosis relies upon confirmation by immunophenotyping of the lineage conversion and certification that the same cytogenetic/molecular alterations remain despite the phenotypic changes. From a total of 1,482 AL pediatric patients, we report nine cases of lineage conversion (0.6%), seven from lymphoid (four Pro-B, two Pre-B, one Common) to myelo-monocytic, and two from myeloid (bilineal, with myeloid predominance) to Pro-B. Eight patients were infants. Switches were suggested by morphology and confirmed with a median of 15 days (range: 8 days-6 months) from initiation of therapy. Of note, in five cases switches occurred before day 15. Stability of the clonal abnormalities was assessed by cytogenetic, RT-PCR/Ig-TCR rearrangement studies in all patients. Abnormalities in 11q23/MLL gene were detected in seven cases. Treatment schedules were ALL (two pts), Interfant-99 (five pts) and AML (two pts) protocols. Despite changing chemotherapy according to the new lineage, all patients died. Our findings support the association of lineage switches with MLL gene alterations and the involvement of a common lymphoid B-myeloid precursor. New therapies should be designed to address these rare cases. Possible mechanisms implicated are discussed.

Hb S-San Martin: a new sickling hemoglobin with two amino acid substitutions [ß6(A3)Glu→Val;ß105(G7)Leu→Pro] in an Argentinean family.

A new sickling hemoglobin (Hb) detected in an Argentinean family from San Martín, Buenos Aires, Argentina, is hereby described. Two mutations were identified on the same ß-globin gene resulting in a new variant named Hb San Martin. One mutation was found on exon 1, corresponding to Hb S [ß6Glu→Val, GAG>GTG] and the second one on exon 3 at ß105(G7)Leu→Pro, CTC>CCC. The replacement of leucine by proline will likely impair the structure breaking helix G and causing instability of the molecule and the clinical manifestations typical of unstable Hbs. The mutation at ß105 seemed to be a de novo one in our patients, arising on a previously mutated gene, due to the fact that Hb S is the most frequent structural variant.

[Erythrocyte indexes in hereditary spherocytosis]. / Indices eritrocitarios en la esferocitosis hereditaria.

Hereditary spherocytosis is a group of heterogenous disorders characterized by variability in its clinical manifestations, membrane protein defects and inheritance. We analysed the sensitivity and specificity of mean corpuscular hemoglobin concentration (MCHC) and red cell distribution width (RDW) in the diagnostic screening of hereditary spherocytosis. Ninety-four patients were compared to equal number of healthy, age-matched children. All indexes were derived from measurements obtained by aperture impedance (Coulter Counter Model JT). In patients with hereditary spherocytosis, MCHC (35.67+/-1.33 g/dl) and RDW (20.60+/-4.5%) were significantly higher than in normal control subjects (MCHC 33.48+/-0.68 g/dl, p: 0.000; RDW 13.22+/-0.9%, p: 0.000). By using a cutoff for the MCHC of 34.5 g/dl and for the RDW of 14.5%, both indexes showed a sensitivity of 81% and a specificity of 98.9%. The combination of the two test is an excellent predictor for the diagnosis of hereditary spherocytosis.

Two novel DNA variants associated with glucose-6-phosphate dehydrogenase deficiency found in Argentine pediatric patients.

OBJECTIVE: The enzyme glucose-6-phosphate dehydrogenase (G6PD) catalyses the first step in the pentose phosphate pathway, producing nicotinamide adenine dinucleotide phosphate (NADPH). NADPH plays a crucial role in preventing oxidative damage to proteins and other molecules in cells, mostly red blood cells. G6PD deficiency has an x-linked pattern of inheritance in which hemizygous males are deficient, while females may or may not be deficient depending on the number of affected alleles. We report two novel DNA variants in the G6PD gene detected in two male probands with chronic nonspherocytic hemolytic anemia (CNSHA), who were referred for hematological evaluation. METHOD: Probands and their relatives underwent clinical, biochemical, and molecular assessment. RESULTS: Two novel DNA variants, c.995C>T and c.1226C>A, were found in this study. At the protein level, they produce the substitution of Ser332Phe and Pro409Gln, respectively. These DNA variants were analyzed in the female relatives of probands for genetic counseling. CONCLUSIONS: The novel DNA variants were classified as class I based on the clinical, biochemical, and molecular evaluations performed.

Experience with four consecutive BFM-based protocols for treatment of childhood with non-promyelocytic acute myeloblastic leukemia in Argentina.

Childhood acute myeloid leukemia (AML) achieves event-free-survival (EFS) rates of ∼50%. Double induction phase has been introduced for improving these results. Four consecutive protocols for AML treatment were evaluated to assess the impact of the addition of a second induction course in our setting. From January 1990 to January 2014, 307 evaluable AML patients were accrued. They were classified into low-risk (LR) and high-risk (HR) according to cytogenetic/molecular findings and response on day 15. The first two studies administered one induction cycle while the latter two protocols administered double induction. Relapse was the most frequent event and early-deaths were reduced by 50% in the last protocol. Statistically significant differences were observed when comparing EFS in LR and HR groups. Patients from both risk-groups who received double induction achieved significantly better outcome. EFS improved in protocols with double induction and early-deaths rate was decreased. Cytogenetic/molecular features and early-response were confirmed as prognostic factors.

[Effect of hydroxyurea on hemoglobin S]. / Efecto de la hidroxiurea en hemoglobina S.

Previous studies have determined the laboratory alterations, clinical efficacy and toxicity profile associated with hydroxyurea (HU) therapy in patients with severe sickle cell anemia. We report the efficacy of HU treatment in the prevention of vaso-occlusive crises in an 11-years-old boy with severe sickle cell disease. The number of vaso-occlusive crises, hospital days and blood transfusions in the year before HU treatment were compared with the same parameters at 6, 12, 24, 36 and 72 months of treatment. A decrease in the frequency of vaso-occlusive crises, blood transfusions and days spent in hospital were demonstrated during the HU treatment period compared to the same period before hand. The clinical and laboratory response to HU was dramatic in this severely affected patient, allowing him a normal schooling and social life. The adverse effects observed were not serious and reversed after transient discontinuation of HU. We conclude that long-term chronic treatment with HU for seriously ill sickle cell patients appears feasible, and devoid of any major toxicity.

Hb Alesha [beta67(E11)Val-->Met, GTG-->ATG] in an Argentinean girl.

Hb Alesha is caused by a GTG-->ATG mutation at codon 67 of the beta-globin gene, resulting in abnormal beta-globin chains in which the normal beta67(E11) valine is changed to methionine. This hemoglobin (Hb) is also known as Hb Bristol, the first unstable Hb described, since in a fraction of the variant the methionine is modified into an aspartic acid by a posttranslational modification. This replacement disrupts the apolar bonds between the valine and the heme group, producing an unstable Hb and severe hemolysis. We have identified this rare hemoglobinopathy in an Argentinean girl with severe hemolytic anemia, splenomegaly and frequent requirement for red blood cell transfusions.

Hb Johnstown [beta109(G11)Val-->Leu]: A high oxygen affinity variant associated with beta0-thalassemia.

Hb Johnstown [beta109(G11)Val-->Leu], a high oxygen affinity hemoglobin (Hb) variant associated with beta0-thalassemia (thal) [IVS-I-1 (G-->A)], was identified in an 8-year-old girl referred to our laboratory because of erythrocytosis and a left-shifted oxygen dissociation curve (ODC). The phylogenetic tree showed that the mother was heterozygous for the Hb variant and the father was a beta0-thal carrier. This Hb variant, with normal electrophoresis, was characterized at the DNA level by beta gene sequencing. The amino acid substitution potentially disrupts alpha1beta1 contacts i n the deoxyHb conformation, thus shifting the equilibrium towards the high affinity oxyHb conformation. The erythrocytosis and low values for actual P50 due to Hb Johnstown were more marked due to the co-inheritance of the beta0-thal.

Efecto de la hidroxiurea en hemoglobina S / Effect of hydroxyurea on hemoglobin S

Previous studies have determined the laboratory alterations, clinical efficacy and toxicity profile associated with hydroxyurea (HU) therapy in patients with severe sickle cell anemia. We report the efficacy of HU treatment in the prevention of vaso-occlusive crises in an 11-years-old boy with severe sickle cell disease. The number of vaso-occlusive crises, hospital days and blood transfusions in the year before HU treatment were compared with the same parameters at 6, 12, 24, 36 and 72 months of treatment. A decrease in the frequency of vaso-occlusive crises, blood transfusions and days spent in hospital were demonstrated during the HU treatment period compared to the same period before hand. The clinical and laboratory response to HU was dramatic in this severely affected patient, allowing him a normal schooling and social life. The adverse effects observed were not serious and reversed after transient discontinuation of HU. We conclude that long-term chronic treatment with HU for seriously ill sickle cell patients appears feasible, and devoid of any major toxicity