Hb I-toulouse [β66(E10)LYS→GLU] in association with α-thalassemia

Hb I-Toulouse in Association with Homozygosity for the α3.7 Deletion in a Pacific Island Woman

“…Both were normocytic and macrocytic, Rosa et al 1 Hendy and Cauchi reported that the differences in laboratory features observed between their two patients, viz microcytosis and lower percentage of Hb I-Touluse, in the presence of similar low iron levels (5 and 9), could be attributed to the difference in the α-globin genotype. 3 The 25 year-old pregnant Solomon Islander's genotype was -α 3.7 /-α 3.7 , whilst the 10-year old child's genotype was αα /-α 3.7 . Similarly, this case was found to have a genotype of -α 3.7 /-α 3.7 in the presence of normal iron and ferritin levels of 23 μmol/L and 273 μg/L respectively.…”

“…2 Two more cases were reported in a 25 year-old pregnant Solomon Islander and her 10-year old paternal cousin. 3 In Hb I-Toulouse the amino acid substitution occurs in the E10 region producing an alteration in the ionic bond between lysine in the position 66 of the β-chain and the propionic chain of the heme giving rise to a slightly unstable ferrihemoglobin associated with a mild hemolytic anemia in the heterozygous state. 2…”

“…reported an MCV of 120 microns3 , and Tejuca et al2 reported value was110 fl. This case and Hendy and Cauchi's 3 25 year-old pregnant Solomon Islander had MCV's of 72 and 78 fl respectively and both showed hypochromia and microcytosis.…”

Hemoglobin I‐Toulouse: A rare hemoglobinopathy presenting with low oxygen saturations

“…Although the association between Hb I‐Toulouse and alpha thalassemia has been seen in the previous case, 5 one case of compound heterozygosity of Hb S‐ and Hb I‐Toulouse presenting with possible vaso‐occlusive episodes has been reported, 4 there is insufficient evidence to define the clinical implications of interactions between Hb I‐Toulouse and other beta‐globin variants such as Hb S or beta thalassemia. Significant medical issues, such as chronic hemolysis or sickle cell disease phenotype, could occur if the Hb I‐Toulouse variant is co‐inherited with other beta‐globin variants, as reported previously 5 . Hence, partner testing and prenatal genetic counseling should be considered in couples where Hb I‐Toulouse and another beta‐globin variant are discovered, since a compound heterozygous state may be associated with an increased risk of hemolysis.…”

“…Hb I‐Toulouse has been described to be unstable and sensitive to spontaneous oxidation 2 . The presentations of the previously reported cases include anemia, 3 joint pain, 4 and symptoms of thalassemia 5 and thrombocytosis, 6 though it is likely that some of these features were due to compound heterozygosity with Hb S and possibly alpha thalassemia in some of these cases 4,5 …”