A novel haemoglobin variant mimicking cyanotic congenital heart disease

Abstract

Screening for critical congenital heart defects in newborn babies can aid in early recognition, with the prospect of improved outcome. However, as this universal newborn screening is implemented, there will be an increasing number of false-positive results. In order to avoid multiple investigations and uncertainty, an haemoglobin (Hb) variant must be included in the differential diagnosis in otherwise well newborns with low oxygen saturation by pulse oximetry. We describe a novel fetal Hb variant (heterozygous γ-globin gene (HBG1) mutation in exon 2 c.202G>A (p.Val68Met)) identified in a newborn with positive pulse oximetry screening for congenital heart disease.

A Hemoglobin Variant Causing an Unexplained Low Oxygen Saturation by Pulse Oximetry: Two Case Reports

“…Moreover, this Hb variant seems to be associated with high oxygen affinity, which may compromise oxygen delivery to tissues and cause mildly elevated lactate [ 3 ], something not present in our cases.…”

“…With these two cases, we aim to raise awareness among clinicians about the existence of this particular Hb variant, only described once previously [3], that may cause low SpO2 but normal SaO2 and PaO2. In newborns, HbF constitutes the largest fraction of Hb [5], and this mutation only affects γ-globin and, therefore, only affects fetal Hb [9].…”

“…Hemoglobinopathies occur when genetic alterations lead to Hb variants, due to the synthesis of a Hb with an abnormal structure, or in thalassemias, due to reduced synthesis of globin chains [ 3 , 6 , 7 ].…”

“…We describe two cases of a Hb variant, caused by mutations in HBG1 exon 2 c.202G>A (p.Val68Met), a mutation that has been reported only once to date [ 3 ].…”

“…hyaline membrane disease), and congenital heart diseases (e.g. Tetralogy of Fallot) but also in the presence of Hb variants, in which PaO2 and SaO2 in arterial blood gas (ABG) samples are normal, but SpO2 is low [3][4][5].…”