Hemoglobin Sunshine Seth: A Case Report of Low-Oxygen-Affinity Hemoglobinopathy

Pulse oximetry is routinely used in the newborn nursery for clinical monitoring and to detect critical congenital heart disease. The differential diagnoses for reduced peripheral oxygen saturation in an infant include congenital heart disease, respiratory distress syndrome, transient tachypnea of the newborn, persistent pulmonary hypertension of the newborn, meconium aspiration syndrome, pneumonia, pneumothorax, and sepsis. The diagnostic evaluation for neonatal hypoxemia can be invasive and expensive. When this evaluation is unrevealing, other interventions may be tried without clear benefit to the patient, including, but not limited to, supplemental oxygen. Therefore, it is important to consider alternative, albeit rare, diagnoses, including hemoglobinopathies with abnormal oxygen binding properties. Mutations in the structure of alpha- and beta-globin chains can alter the affinity of hemoglobin for oxygen, and changes in oxygen affinity may result in changes in the oxygen saturation detected by pulse oximetry. These changes may or may not be of clinical significance. This case report describes Hemoglobin Sunshine Seth, a rare low-oxygen-affinity hemoglobin variant presenting as reduced peripheral oxygen saturation in an otherwise well-appearing infant male.

Family case hemolytic anemia due to abnormal unstable hemoglobin with low oxygen affinity (Hb Cheverly)

Hereditary hemolytic anemia caused by unstable hemoglobin is a rare pathology, characterized by variability of clinical manifestations. This disease is characterized by the hemolytic crises, which are frequently associated with infections or taking drugs that cause hemolysis. Age of debut depends on which of the globin chains mutation occurs. Among these diseases, hemolytic anemia associated with the presence of a structurally abnormal unstable hemoglobin with low oxygen affinity in the erythrocytes is a special group. With this type of abnormal hemoglobin, pulse oximetry demonstrates falsely low oxygen saturation of the blood, with increased oxygen delivery to the tissues. It is important to identify unstable hemoglobin in order to avoid the misinterpretation of low oxygen saturation during the pulse oximetry in emergency cases, surgeries or intensive therapy. The article presents an analysis of the family with hereditary hemolytic anemia due to unstable hemoglobin Cheverly. The main clinical and diagnostic markers of the disease are described in detail. Parents gave their permission for using personal data for clinical research and publications.

Oxygenation during general anesthesia and thoracic surgery in a patient with Titusville low-oxygen affinity hemoglobin

The purpose of this case study is to describe the physiological characteristics of a patient with the low-oxygen affinity Titusville hemoglobin variant. A 46-yr-old man with exertional dyspnea was diagnosed with a mediastinal lymphadenopathy of unknown origin and, to obtain definitive diagnosis by biopsy, underwent endobronchial ultrasound-guided transbronchial needle aspirate under sedation and video-assisted thoracoscopy under general anesthesia. High inspired fraction of oxygen ([Formula: see text]) was used to guarantee adequate oxygenation even during the one-lung ventilation needed for thoracoscopy. Following radial and pulmonary arterial catheterization, continuous mixed-venous oxygen saturation ([Formula: see text]), cardiac output, oxygen delivery (DO2), oxygen consumption (V̇o2), and oxygen extraction ratio (ERO2) were measured. Serial blood gas analyses were obtained at different [Formula: see text]. Anesthesia and surgery were carried out safely. Data obtained during the clinical case were utilized to 1) construct an in vivo Titusville hemoglobin dissociation curve and 2) describe oxygen delivery and consumption of a human with Titusville mutation. Titusville hemoglobin showed relatively high P50 (i.e., 30 vs. normal of 27) and very low cooperativity (Hill coefficient of 1.45 vs. normal 2.27), which was compensated in our patient by increases in cardiac output, rather than by augmenting oxygen extraction.

Engineering oxidative stability in human hemoglobin based on the Hb providence (βK82D) mutation and genetic cross-linking

Previous work suggested that hemoglobin (Hb) tetramer formation slows autoxidation and hemin loss and that the naturally occurring mutant, Hb Providence (HbProv; βK82D), is much more resistant to degradation by H2O2. We have examined systematically the effects of genetic cross-linking of Hb tetramers with and without the HbProv mutation on autoxidation, hemin loss, and reactions with H2O2, using native HbA and various wild-type recombinant Hbs as controls. Genetically cross-linked Hb Presbyterian (βN108K) was also examined as an example of a low oxygen affinity tetramer. Our conclusions are: (a) at low concentrations, all the cross-linked tetramers show smaller rates of autoxidation and hemin loss than HbA, which can dissociate into much less stable dimers and (b) the HbProv βK82D mutation confers more resistance to degradation by H2O2, by markedly inhibiting oxidation of the β93 cysteine side chain, particularly in cross-linked tetramers and even in the presence of the destabilizing Hb Presbyterian mutation. These results show that cross-linking and the βK82D mutation do enhance the resistance of Hb to oxidative degradation, a critical element in the design of a safe and effective oxygen therapeutic.

Hemoglobin variants – pathomechanism, symptoms and diagnosis

The diagnosis of hemoglobin variants that are not any of the better-known forms of thalassemia, sickle cell, HbC, HbD, or HbE anomalies is often challenging and requires detailed knowledge of the difference in symptoms and analysis. Experience in laboratory medicine plays an important role as the range of variants is extensive and lack of expertise can result in a wrong diagnosis. Hemoglobin variants with low oxygen affinity may present cyanosis and low oxygen saturation levels, whereas variants with increased oxygen affinity show polyglobulia and concomitant complications. Differential diagnosis of methemoglobin variants requires careful assessment, which can be problematic especially in pediatric medicine. Other variants, due to their instability, can cause more or less distinct hemolysis or thalassemia syndromes depicting serious disease patterns. Clear distinction is not always possible as several symptoms are often present. Many variants are autosomal dominant inherited.