Voxelotor Treatment Interferes With Quantitative and Qualitative Hemoglobin Variant Analysis in Multiple Sickle Cell Disease Genotypes

Objectives Voxelotor was recently approved for use in the United States as a treatment for sickle cell disease (SCD) and has been shown to interfere with the quantitation of hemoglobin (Hb) S percentage. This study aimed to determine the effect of voxelotor on the quantitation of hemoglobin variant levels in patients with multiple SCD genotypes. Methods In vitro experiments were performed to assess the impact of voxelotor treatment on hemoglobin variant testing. Whole blood samples were incubated with voxelotor and then analyzed by routinely used quantitative and qualitative clinical laboratory methods (high-performance liquid chromatography [HPLC], capillary zone electrophoresis [CZE], and acid and alkaline electrophoresis). Results Voxelotor modified the α-globin chain of multiple hemoglobins, including HbA, HbS, HbC, HbD-Punjab, HbE, HbA2, and HbF. These voxelotor-hemoglobin complexes prevented accurate quantitation of multiple hemoglobin species, including HbS, by HPLC and CZE. Conclusions Technical limitations in quantifying HbS percentage may preclude the use of HPLC or CZE for monitoring patients treated with voxelotor. Furthermore, it is unclear whether HbS-voxelotor complexes are clinically equivalent to HbS. Consensus guidelines for reporting hemoglobin variant percentages for patients taking voxelotor are needed, as these values are necessary for determining the number of RBC units to exchange in acute situations.

Coinheritance of HbD-Punjab/β+-thalassemia (IVSI+5 G-C) in patient with Gilbert's syndrome

Thalassemia and qualitative hemoglobinopathy are hereditary disorders of Hb synthesis that lead to change in the Hb conformation or a decrease in the synthesis of structurally normal Hb, and consequently, to erythron pathology. Many variants of Hb are unstable or have altered affinity for oxygen, and, in heterozygous form can be associated with clinical and hematological manifestations (hemolytic anemia, hypochromic microcytic anemia, erythrocytosis). HbD-Punjab [β121 (GH4) Glu → Gln; HBB: C.364G> C] is variant of Hb carrying the amino acid substitution in the 121 position of β-globin chain. In all cases reported so far, patients with HbD-Punjab/β+-thalassemia (IVSI+5 G-C) combination experienced typical thalassemia with hypochromic microcytosis. HbD-Punjab was detected by electrophoresis from 37 to 94% of total Hb. The article describes rare clinical case of the cohabitation of HbD-Punjab/β+-thalassemia (IVSI+5 G-C) in a patient with homozygous variant of Gilbert's syndrome observed in AS Loginov Moscow Clinical Scientific Center.

Coexistence of rare variant HbD Punjab [α2β2121(Glu→Gln)] and alpha 3.7 kb deletion in a young boy of Hindu family in West Bengal, India

HbD Punjab is a variant of hemoglobin which occurs as a result of mutation in codon 121 (GAA>CAA) of the β-globin gene, which replaces glutamic acid with glutamine (Glu→Gln). The heterozygous state of HbD does not produce any clinical or hematological symptoms, although its association with HbS and thalassemia produces clinically significant but less severe conditions. The homozygous state produces mild hemolytic anemia and mild to moderate splenomegaly. Alpha-thalassemia is characterized by reduction or absence of the α-globin chains due to deletional or non-deletional mutations of α-globin genes located on chromosome 16. The present study describes a Hindu family where both HbD Punjab and alpha 3.7 kb deletion are present among the members in the heterozygous and double heterozygous state. Comparison of clinical and hematological parameters between the heterozygous and double heterozygous state of HbD and the alpha 3.7 kb deletion is also discussed here. According to our study, the prevalence rate of HbD Punjab is very low, i.e. 0.06%.

HbD Punjab/HbQ India compound heterozygosity: An unusual association.

Background: Haemoglobinopathies are the commonest hereditary disorders in India and pose a major health problem. Both beta thalassaemia and structural haemoglobin variants are relatively common in north western India. Here we report a 29 year old Sindhi female who was referred to us for a haemoglobinopathy work up and genetic counseling since her spouse was a classical beta thalassaemia carrier. Method: A complete blood count was done on an automated cell counter. Haemoglobin analysis was carried out using HPLC Variant Haemoglobin Testing System. The cellulose acetate electrophoresis was carried out [pH 8.9]. Confirmation of mutations was done by automated DNA sequencing. Results: HPLC analysis showed four major peaks, HbA0, a peak in the HbD window, an unknown peak [retention time 4.74 minutes] and a peak in the HbC window. The HbA2 level was 2.2% and the HbF level was 0.7%.Cellulose acetate electrophoresis at alkaline pH, a slow moving band was seen at the HbS/D position along with a prominent band at the HbA2 position. DNA sequencing of the β and α genes showed presence of the 2 hemoglobin variants :Hb D [b 121GAA à CAA] and Hb Q [a 64 AAG à GAG]. The δ globin gene was normal. The additional peak in the HbC window was due to the formation of a heterodimer hybrid. Conclusion: Both HbD Punjab and HbQ India are relatively common in India but their co-inheritance has not been described in the country. This is the second report of compound heterozygosity for HbQ India/HbD Punjab haemoglobinopathy globally, and the first one from India.