Hb Kirikiriroa [α57(E6)Gly→Cys; HBA1: c.172G>T]: A Novel Unstable α-Globin Variant with Oxidized Derivatives Interfering with Hb A1c.

We report the identification of a novel hemoglobin (Hb) variant [α57(E6)Gly→Cys; HBA1: c.172G>T], to be referred to as Hb Kirikiriroa. The variant was detected in five subjects from two families, with familial relationship established between the families following diagnosis. A persistently elevated Hb A1c over a 1-year period prompted hemoglobinopathy screening in an adolescent male of New Zealand (NZ) European descent (case 1). Capillary electrophoresis (CE) revealed the variant was negatively charged and susceptible to oxidation, with multiple abnormal peaks detected (0.4-5.1% total Hb). Hb A1c analysis by cation exchange high performance liquid chromatography (HPLC) was the first indication of the variant in a pregnant female of NZ European descent (case 2). Cases 1 and 2 had normal complete blood counts. Isopropanol stability testing provided evidence the variant was unstable. We herein describe the characterization of Hb Kirikiriroa and clinical significance of the variant for interference with Hb A1c analysis by CE and cation exchange HPLC.

Hb Tacoma: G>T or G>C, and Does It Matter?

Hb Tacoma [ß30(B12)Arg→Ser] is a missense variant that is caused by either an AGG>AGT or AGG>AGC substitution at codon 30 of the HBB gene. Currently, the latter is classified as a rare cause of ß0-thalassemia (ß0-thal). We propose that HBB: c.93G>C has been incorrectly assigned as ß0-thal and discuss whether HBB: c.93G>T or HBB: c.93G>C should be classified as ß+-thal instead, or as ß-globin variants without thalassemic effect. We present several subjects who are heterozygous for Hb Tacoma, one with HBB: c.93G>T and two with HBB: c.93G>C, to support our conclusions.

Hb Waikato [α127(H10)Lys→Gln; HBA1: c.382A>C]: A Novel High Oxygen Affinity Variant.

We report the identification of a novel, high oxygen affinity hemoglobin (Hb) variant [α127(H10)Lys→Gln; HBA1: c.382A>C]. The variant was detected in an adolescent male (proband) of Syrian descent by cation exchange high performance liquid chromatography (HPLC), during Hb A1c analysis. A complete blood count (CBC) showed elevated red blood cells (RBCs) (6.08 × 1012/L), Hb (16.1 g/dL) and packed cell volume (PCV) (0.48 L/L). Capillary electrophoresis (CE) revealed the variant was more negatively charged and represented 18.2% of total Hb. Isopropanol stability was normal. Cyanosis in the subject prompted investigation of oxygen affinity, with a reduced p50 of 20.8 mm Hg and a left shifted oxygen dissociation curve demonstrating increased oxygen affinity. We propose the novel variant be named Hb Waikato, which reflects the Hospital Laboratory where the variant was discovered and region where the proband was born and herein describe characterization.

Novel α0-Thalassemia Deletion Identified in an Indian Infant with Hb H Disease.

We report the identification of a large deletion of the α-globin gene cluster, which removed both HBA2 and HBA1 and included the region from HBZ to HBQ1 on chromosome 16 (16p13.3). The α0-thalassemia (α0-thal) deletion was discovered in an Indian family residing in New Zealand. The proband was a 3-month-old female, who presented with a Hb H disease of unknown molecular origin. Routine hematology showed marked hypochromic microcytic anemia, with numerous Hb H inclusion bodies. In the absence of iron deficiency, there was a strong clinical suspicion of α-thal. On initial screening using a multiplex gap polymerase chain reaction (gap-PCR), only the common rightward deletion (-α3.7) was detected. Investigation of the proband's mother and father revealed the mother was heterozygous for the -α3.7 deletion, while none of the seven most common pathogenic α-thal deletions were detected in the father. Multiplex ligation-dependent probe amplification (MLPA) was employed to detect the presence of a novel α0-thal deletion in both the proband and her father. For the proband, the α0-thal deletion in combination with the -α3.7 deletion, eliminated three copies of HBA consistent with a clinical diagnosis of Hb H disease.

Hb Manitoba [α102(G9)Ser→Arg] in Pasifika: Tongan Case Report.

Hb Manitoba [α102(G9)Ser→Arg] results from an AGC>CGC or AGC>AGA substitution at codon 102 of the HBA1 or HBA2 genes. The variant is mildly unstable but carriers typically have normal clinical presentation and hematological profile. Hb Manitoba has not been reported in Pasifika of Tongan, Samoan or New Zealand (NZ) Maori descent before. The cases presented here support the findings from existing literature but include results from alternative methodology including capillary zone electrophoresis (CZE), which may slightly underestimate the true variant percentage. The subject of our case report, a Tongan male with microcytic indices, was shown to be heterozygous for Hb Manitoba III (HBA2: c.309C>A) coinherited with the -α3.7 (rightward) deletion.

Relationship of the Cricothyroid Space with Vocal Range in Female Singers.

OBJECTIVES: This study aims to investigate the relationship between the anterior cricothyroid (CT) space at rest with vocal range in female singers. Potential associations with and between voice categories, age, ethnicity, anthropometric indices, neck dimensions, laryngeal dimensions, vocal data along with habitual speaking fundamental frequency were also explored. STUDY DESIGN: This is a cohort study. METHODS: Laryngeal dimensions anterior CT space and heights of the thyroid and cricoid cartilages were measured using ultrasound in 43 healthy, classically trained, female singers during quiet respiration. Voice categories (soprano and mezzo-soprano), age, ethnicity, weight, height, body mass index, neck circumference and length, anterior thyroid and cricoid cartilage heights, practice and performance vocal range, lowest and highest practice and performance notes along with habitual speaking fundamental frequency were collected. RESULTS: The main finding was that mezzo-sopranos have a significantly wider resting CT space than sopranos (11.6 mm versus 10.4 mm; P = 0.007). Mezzo-sopranos also had significantly lower "lowest and highest" performance notes than sopranos. There was no significant correlation between the magnitudes of the anterior CT space with vocal range. The participants with the narrowest and widest anterior CT space had similar vocal ranges. CONCLUSIONS: These results suggest that the CT space is not the major determinant of performance vocal range.

Novel haemoglobin mutation (α127Lys→Glu) increases oxygen affinity and has a minor effect on haptoglobin binding.

OBJECTIVES: To determine if a new haemoglobin (Hb) variant was the underlying cause of erythrocytosis in a subject with a high apparent HbA(1)c. DESIGN AND METHOD: Haemolysate was analysed by ESI MS, and individual components purified by ion exchange and reverse phase chromatography. Peptide mapping was used to pinpoint the substitution and DNA sequencing to confirm the precise mutation. Oxygen affinity was measured and relative haptoglobin (Hp) binding estimated. RESULTS: Intact protein analysis and peptide mapping suggested a mutation in peptide α13 and DNA sequencing confirmed a novel α127Lys→Glu substitution in the α 2 gene. The abnormal Hb had a significantly higher O(2) affinity (5.8 mmHg) than HbA (12.4 mmHg). In addition the mutation caused a small but significant decrease in Hp binding. CONCLUSION: Molecular models show that the side chain of α127Lys stabilises the T structure of deoxy Hb and that mutation to Glu would favour conversion to the high affinity R state. Notwithstanding this and the demonstrated high affinity, there was only a small increase in RBCs, Hb concentration and PCV in other female carriers of the mutation. The absence of a significant phenotype of erythrocytosis is most probably due to the low level (19%) of the variant.