LAUSR

Dear Editor, Hb Kirklareli was first described—and has to date only been reported—by Bissé et al. in 2017 [1] in a 23-year-old Turkish woman from the city of Kirklareli who presented with anemia associated with iron deficiency. Molecular analysis of the α globin genes and mass spectrometry of the patient’s Hb peptides revealed the α1 H59L mutation (HBA1:c.176A>T] (according to Human Genome Variation Society-HGVS nomenclature). The patient’s father was also a carrier of the mutation. A heavy smoker, he did not present with anemia but had abnormally high HbCO levels (around 16%). Structural and biophysical analyses demonstrated that the oxygenated form of Hb Kirklareli denatures very quickly under physiological conditions as the mutant α subunits undergo autoxidation and lose the heme more quickly than the native α subunits. The α H59L subunits, in contrast, have much greater affinity for CO than for O2, preventing denaturation of the variant both in vitro and in vivo and explains the phenotypic differences between the patient and her father [1]. We detected Hb Kirklareli in an 11-year-old male Brazilian patient of Portuguese descent who had been admitted to the University Hospital, Unicamp. The patient presented with chronic obstructive respiratory insufficiency, and even after the obstruction had been resolved, O2 saturation remained low (86–88%). He had a history of wheezing in the first year of life, and the episodes of dyspnea and bronchoconstriction restarted when he was 7 years old. The episodes were associated with physical effort and changes in the weather, and the patient was admitted to hospital on sporadic occasions. Although the child was already being treated for bronchial asthma (formoterol + budesonide and prophylactic azithromycin), no wheezes were heard on lung auscultation during exacerbations. Computed tomography of the thorax and ventilation/perfusion lung scan were unremarkable. The definitive diagnosis was atopic asthma. After the parents had given their voluntary consent, peripheral blood samples were collected from the family. The hematologic and biochemical data for the patient and his parents are shown in Table 1. Only the father, who was diabetic and hypertensive, presented with anemia (normocytic and normochromic), while a slight reduction in iron was observed in both father and son; serum ferritin levels were within normal range. Cation-exchange high-performance liquid chromatography (HPLC) (VARIANT IITM; Bio-Rad Laboratories, Hercules, CA, USA) failed to reveal any additional elution peak, but the fact that the baseline was distorted (Supplementary Material Figure 1A) indicates that the hemolysate could usefully have been analyzed further. Reverse-phase HPLC (Waters Corporation, Milford, MA, USA) revealed the abnormal α chain (which accounted for 15% of the total globin), with a longer elution time than the normal α chain (SupplementaryMaterial Figure 1B). Tests to detect unstable Hb intra-erythrocyte bodies were negative [2]. Sequencing of the HBA1 and HBA2 genes (ABI PRISM® 3500, Applied Biosystems, Foster City, CA, USA) revealed the CAC→CTC substitution at codon 59 (HGVS nomenclature) of the HBA2 gene, which results in Hb Kirklareli [α2 Gisele Audrei Pedroso and Patricia Fernandes contributed equaly to the work.