Lip cyanosis as the first symptom of Leigh syndrome associated with mitochondrial complex I deficiency due to a compound heterozygous NDUFS1 mutation: A case report

BACKGROUND

Leigh syndrome (LS) is a rare, progressive, and fatal neurodegenerative disease that occurs mainly in infants and children. Neonatal LS has not yet been fully described.

METHODS

The study design was approved by the ethics review board of Shenzhen Children's Hospital.

RESULTS

A 24-day-old full-term male infant presented with a 2-day history of lip cyanosis when crying in September 2021. He was born to nonconsanguineous Asian parents. After birth, the patient was fed poorly. A recurrent decrease in peripheral oxygen saturation and difficulty in weaning from mechanical ventilation during hospitalization were observed. There were no abnormalities on brain magnetic resonance imaging (MRI) or blood and urine organic acid analyses on admission. His lactic acid level increased markedly, and repeat MRI showed symmetrical abnormal signal areas in the bilateral basal ganglia and brainstem with disease progression. Trio whole-exome sequencing revealed 2 heterozygous mutations (c.64C > T [p.R22X] and c.584T > C [p.L195S]) in NDUFS1. Based on these findings, mitochondrial respiratory chain complex I deficiency-related LS was diagnosed. The patient underwent tracheal intubation and mechanical ventilation for respiratory failure. His oxygen saturation levels were maintained at normal levels with partially assisted ventilation. He was administered broad-spectrum antibiotics, oral coenzyme Q10, multivitamins, and idebenone. During hospitalization, the patient developed progressive consciousness impairment and respiratory and circulatory failure. He died on day 30.

CONCLUSION

Lip cyanosis is an important initial symptom in LS. Mild upper respiratory tract infections can induce LS and aggravate the disease. No abnormal changes in the brain MRI were observed in the early LS stages in this patient. Multiple MRIs and blood lactic acid tests during disease progression and genetic testing are important for prompt and accurate diagnosis of LS.

The First Korean Family with Hemoglobin-M Milwaukee-2 Leading to Hereditary Methemoglobinemia

Hemoglobin M (HbM) is a group of abnormal hemoglobin variants that form methemoglobin, which leads to cyanosis and hemolytic anemia. HbM-Milwaukee-2 is a rare variant caused by the point mutation CAC>TAC on codon 93 of the hemoglobin subunit beta (HBB) gene, resulting in the replacement of histidine by tyrosine. We here report the first Korean family with HbM-Milwaukee-2, whose diagnosis was confirmed by gene sequencing. A high index of suspicion for this rare Hb variant is necessary in a patient presenting with cyanosis since childhood, along with methemoglobinemia and a family history of cyanosis.

[BLUE BABY, PINK FUTURE]

Neonatal cyanosis is relatively common. It is usually a consequence of cyanotic heart disease or a pulmonary disorder, and warrants a thorough and quick investigation. Mutations causing decreased affinity of hemoglobin to oxygen may change α1 to β2 binding. We describe a new mutation (asp 102 serine), in the γ chain of hemoglobin, causing neonatal cyanosis which resolves as the baby matures. In this case we would like to emphasize the importance of early diagnosis in order to avoid unnecessary disease workup.

Lung microRNA profile in chronic cyanotic piglets with decreased pulmonary blood flow

BACKGROUND

Cyanotic congenital heart defects with decreased pulmonary blood flow due to lung ischemia, hypoxia, and others lead to infant morbidity and mortality more than acyanotic heart disease does. Despite the great effort of medical research, their genetic link and underlying microRNAs molecular mechanisms remain obscure. In this study, we aimed to investigate microRNAs regulation during cyanotic defects in lung of immature piglets.

METHODS

Cyanotic piglet model was induced by main pulmonary artery-left atrium shunt with distal pulmonary artery banding. Four weeks later, hemodynamic parameters confirmed the development of cyanotic defects and pulmonary lobe RNA was extracted from all animals. We studied the repertoire of porcine lung microRNAs by Solexa deep sequencing technology and quantified highly expressed microRNAs by microarray hybridization. Furthermore, we quantitated selected microRNAs from cyanotic and control piglets by quantitative RT-PCR.

RESULTS

After surgical procedure 4 weeks later, the cyanotic model produced lower arterial oxygen tension, arterial oxygen saturation, and higher arterial carbon dioxide tension, hematocrit and hemoglobin concentration than controls (all P < 0.05). In 1273 miRNAs expressed in the immature piglets lungs, 2 most abundant microRNAs (miR-370 and miR-320) demonstrated significant difference between cyanotic and control group (all P < 0.05).

CONCLUSION

Our results extended lung microRNA profile in immature piglets and suggested that miR-370 and miR-320 are significantly up-regulated in cyanotic lung tissues.

PHOX2B mutations in patients with Ondine-Hirschsprung disease and a review of the literature

Congenital central hypoventilation syndrome (CCHS), also known as Ondine's curse, is characterized by idiopathic failure of autonomic breathing and is often associated with neurocristopathies such as Hirschsprung disease (HSCR). CCHS is caused by mutations in the paired-like homeobox 2B (PHOX2B) gene, often manifest as polyalanine repeat expansions. Herein, we report the cases of two unrelated Korean patients with Ondine-Hirschsprung disease. The patient's clinical manifestations were apnea and cyanosis requiring immediate endotracheal intubation, recurrent hypoventilation with hypercapnia, hypoxia after ventilator removal, and abdominal distension since birth. Intestinal biopsies were performed and the absence of ganglion cells in the colon was consistent with HSCR. We performed direct sequencing analysis in the PHOX2B and RET genes and fluorescence polymerase chain reaction in order to determine the polyalanine tract expansion in exon 3 of the PHOX2B gene. Expansion mutations were detected in both patients; one had 20/24 repeats and the other had 20/27 repeats. The 20/24 genotype has not been previously described in severe CCHS phenotypes and associated HSCR. We believe that the information in this report will improve our understanding of the phenotypic and genotypic heterogeneities of CCHS and HSCR.

A hemoglobin variant associated with neonatal cyanosis and anemia

Globin-gene mutations are a rare but important cause of cyanosis. We identified a missense mutation in the fetal Gγ-globin gene (HBG2) in a father and daughter with transient neonatal cyanosis and anemia. This new mutation modifies the ligand-binding pocket of fetal hemoglobin by means of two mechanisms. First, the relatively large side chain of methionine decreases both the affinity of oxygen for binding to the mutant hemoglobin subunit and the rate at which it does so. Second, the mutant methionine is converted to aspartic acid post-translationally, probably through oxidative mechanisms. The presence of this polar amino acid in the heme pocket is predicted to enhance hemoglobin denaturation, causing anemia.

The hypoxia-inducible factor HIF-1 promotes intramyocardial expression of VEGF in infants with congenital cardiac defects

OBJECTIVES

The response to hypoxia is primarily mediated by the transcription factor hypoxia-inducible factor-1 (HIF-1) which leads to the induction of a variety of adaptive gene products including vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS). This study was designed to test the hypothesis that HIF-1 and its target genes would be upregulated in the ventricular myocardium of infants with cyanotic congenital cardiac defects.

METHODS

14 infants with cyanotic (n = 7) or acyanotic cardiac defects (n = 7) were investigated. Samples from the right ventricular myocardium taken immediately after aortic clamping were studied for protein expression and DNA-binding activity.

RESULTS

Protein levels of HIF-1alpha were significantly elevated in patients with cyanotic compared to acyanotic congenital heart disease and inversely correlated with the degree of hypoxemia. This response was accompanied by significantly enhanced HIF-1 DNA binding activity. Furthermore, protein levels of VEGF and eNOS were significantly higher in the myocardium of cyanotic than of acyanotic infants. To test the potential involvement of upstream regulatory pathways, activation of MAP kinases was determined. Intramyocardial levels of phosphorylated p38 MAP kinase, but not of ERK1/2 were significantly higher in infants with cyanotic compared to those with acyanotic congenital heart disease and inversely correlated to hypoxemia.

CONCLUSIONS

These findings show that chronic hypoxemia is associated with the induction and stabilization of the transcription factor HIF-1 as well as its target genes VEGF and eNOS in the myocardium of infants with cyanotic cardiac defects. Thus, stabilization of HIF-1 and induction of the adaptive hypoxia response could particularly participate in myocardial remodeling in children with congenital cardiac defects and chronic hypoxemia.

Congenital methemoglobinemia caused by Hb-MRatnagiri (beta-63CAT-->TAT, His-->Tyr) in an Indian family

Hb-M is a very rare hemoglobinopathy in the Indian subcontinent. We report a family with Hb-M with lifelong cyanosis from the Ratnagiri district in western India. The propositus was a 11-year-old female child with a history of increasing cyanosis exacerbated by fever and weakness. Similar complaints were also noted in her mother and five maternal family members. There was no history of cardiac illness or exposure to drugs and chemicals. The methemoglobin level was 39.3% in the propositus and 21.1% in her mother with normal NADH-methemoglobin reductase activity. Abnormal absorption peaks by spectroscopic analysis, presence of hemoglobin instability, and a slow-moving band on starch gel electrophoresis supported the presence of Hb-M. Automated DNA sequence analysis of the beta globin gene showed a C-->T substitution at codon 63. This leads to a substitution of histidine (CAT) by tyrosine (TAT) at the beta 63 (E7) position, similar to Hb-M Saskatoon. We have named this variant as Hb-M(Ratnagiri).

Gene targeting reveals a widespread role for the high-mobility-group transcription factor Sox11 in tissue remodeling

The high-mobility-group domain-containing transcription factor Sox11 is expressed transiently during embryonic development in many tissues that undergo inductive remodeling. Here we have analyzed the function of Sox11 by gene deletion in the mouse. Sox11-deficient mice died at birth from congenital cyanosis, likely resulting from heart defects. These included ventricular septation defects and outflow tract malformations that ranged from arterial common trunk to a condition known as double outlet right ventricle. Many other organs that normally express Sox11 also exhibited severe developmental defects. We observed various craniofacial and skeletal malformations, asplenia, and hypoplasia of the lung, stomach, and pancreas. Eyelids and the abdominal wall did not close properly in some Sox11-deficient mice. This phenotype suggests a prime function for Sox11 in tissue remodeling and identifies SOX11 as a potentially mutated gene in corresponding human malformation syndromes.

Congenital methemoglobinemia due to NADH-methemoglobin reductase deficiency in three Indian families

Congenital methemoglobinemia is a relatively rare clinical disorder characterized by life-long cyanosis, caused by either an inherited mutant hemoglobin (Hb-M) or deficiency of physiologically active NADH-dependent methemoglobin reductase (NADH-MR). NADH-MR deficiency leads to two different types of recessive congenital methemoglobinemia. In type I, cyanosis is the only major symptom and NADH-MR deficiency is restricted only to the red blood cells. In type II, cyanosis is associated with severe mental retardation and neurological impairment. The objective of this study is to establish the cause of cyanosis in our cases of congenital methaemoglobinemia. Erythrocyte NADH-MR activity was assayed spectrophotometrically. Spectral analysis of the hemolysate treated with potassium ferricyanide was recorded between 400-700 nm and Hb electrophoresis on starch gel at pH 7.0 was done to rule out the presence of Hb-M. NADH-MR deficiency was detected in 3 families. There was a history of consanguinity in one of these cases. The three propositi presented with breathlessness, fever and peripheral cyanosis. There was no history of cardiac illness or exposure to drugs and chemicals. There were no signs and symptoms of mental retardation. The presence of Hb-M was ruled out. Hb-A2, Hb-F, G6PD activity and reduced glutathione levels were normal. NADH-MR activity in all the cases ranged from 4.1 to 9.2 IU/g Hb (normal range 7.0-24.0 IU/g Hb). We describe NADH-MR deficiency in three unrelated cases (age 4 months to 6 years) where the activity of the enzyme was 30-40% of normal. These three cases of congenital methemoglobinemia are due to type-I NADH-MR deficiency without mental retardation.

Rnx deficiency results in congenital central hypoventilation

The genes Tlx1 (Hox11), Enx (Hox11L2, Tlx-2) and Rnx (Hox11L2, Tlx-3) constitute a family of orphan homeobox genes. In situ hybridization has revealed considerable overlap in their expression within the nervous system, but Rnx is singularly expressed in the developing dorsal and ventral region of the medulla oblongata. Tlx1-deficient and Enx-deficient mice display phenotypes in tissues where the mutated gene is singularly expressed, resulting in asplenogenesis and hyperganglionic megacolon, respectively. To determine the developmental role of Rnx, we disrupted the locus in mouse embryonic stem (ES) cells. Rnx deficient mice developed to term, but all died within 24 hours after birth from a central respiratory failure. The electromyographic activity of intercostal muscles coupled with the C4 ventral root activity assessed in a medulla-spinal cord preparation revealed a high respiratory rate with short inspiratory duration and frequent apnea. Furthermore, a coordinate pattern existed between the abnormal activity of inspiratory neurons in the ventrolateral medulla and C4 motorneuron output, indicating a central respiratory defect in Rnx mice. Thus, Rnx is critical for the development of the ventral medullary respiratory centre and its deficiency results in a syndrome resembling congenital central hypoventilation.

Hemoglobin F-Cincinnati, alpha 2G gamma 2 41(C7) Phe-->Ser in a newborn with cyanosis

A term infant presented with mild cyanosis without evidence of hypoxia. Cardiopulmonary disease, polycythemia, and methemoglobinemia were excluded. Standard hemoglobin electrophoresis, including isoelectric focusing, were normal. However, by reverse-phase C4 HPLC, an abnormal globin chain was detected. Analysis of tryptic peptides and amino acid sequence showed that the patient had an amino acid substitution Phe-->Ser at residue 41(C7) in the G gamma chain. This was confirmed by DNA sequencing that demonstrated a point mutation at the expected site in exon 2 of the G gamma gene, accounting for the appropriate change in the codon. This substitution, hemoglobin F-Cincinnati, alpha 2 gamma 2 41(C7) Phe-->Ser, not previously described, presumably decreased oxygen affinity of the hemoglobin. This substitution is very near the heme group and the alpha 1 beta 2 interface and, hence, in a crucial area of the globin chain. Abnormalities of gamma globin chains tend to be overlooked due to their transient presence and trivial clinical symptomatology, or due to "in utero" selection when physiologically abnormal. Mutant hemoglobins with altered oxygen affinity should be included in the differential diagnosis of newborns presenting with cyanosis, in whom all common causes have been excluded.

[Hb M-Iwate [alpha 87 (F8) His-->Tyr]: analysis of the genomic DNA and biosynthesis]

Hb M-Iwate [alpha 87 (F8) His-->Tyr] was identified as the cause of cyanosis in a 21-year-old Japanese female. Amplification and sequencing of the alpha 2- and alpha 1-genes demonstrated the mutation CD87 CAC (His)-->TAC (Tyr) in the alpha 2-gene. Analysis of the in vitro globin biosynthesis in the reticulocytes disclosed a well-balanced beta/alpha synthetic ratio of 1.04 but an unexpectedly low alpha M/total alpha. Although the cause of the lowered alpha M-globin biosynthesis is not yet clear, it might be related to a defect in chain assembly rather than to a modified stability or a reduced amount of the abnormal alpha-globin mRNA.

Hemoglobin Denver [alpha 2 beta 2(41) (C7) Phe-->Ser]: a low-O2-affinity variant associated with chronic cyanosis and anemia

OBJECTIVE

To report a previously undescribed low-O2-affinity hemoglobin variant that is associated with chronic cyanosis.

DESIGN

Pertinent laboratory and historical data for the index case (from Denver, Colorado) and certain family members were recorded, and the hemoglobin variant was characterized.

MATERIAL AND METHODS

Electrophoresis, high-performance liquid chromatography (HPLC), and isoelectric focusing were used to examine blood specimens for the presence of hemoglobin variants, and the O2 affinity of whole blood was determined. The abnormal peptide detected on reverse-phase HPLC of separated globin chains was analyzed for its amino acid composition and sequence.

RESULTS

Although no abnormal hemoglobin band separated from hemoglobin A on electrophoresis, HPLC, and isoelectric focusing, a heat test showed hemoglobin instability, and O2 affinity studies disclosed an appreciably right-shifted dissociation curve. On chromatography, the new variant--hemoglobin Denver--was found to be due to a substitution of serine for phenylalanine at position 41 (C7) in the beta chain. In addition to substantial reduction in O2 affinity, hemoglobin Denver is accompanied by moderate reticulocytosis and mild anemia.

CONCLUSION

Hemoglobin Denver causes no clinical symptoms other than cyanosis, which is attributable to the low O2 affinity.

Hemoglobin Kansas found in a patient with polycythemia

A 62-year-old woman, long suspected of having heart disease, was admitted to our hospital for thorough examination. Her hemoglobin level was 17.7 g/dl and her 2.3-DPG level was 8.90 microM/ml RBC. The patient proved to have polycythemia, hemoglobin Kansas, and diabetes mellitus. To our knowledge, this is the third case of hemoglobin Kansas in the world.

Familial cyanotic breath-holding spells

Breath-holding spells can be a source of considerable parental anxiety and are a frequent cause of referral to paediatric services. This report is of a family of seven siblings all of whom have suffered breath-holding spells, including three who developed breath-holding spells within the neonatal period, with the other four developing them at 3-4 months of age. All of the children have on occasions exhibited convulsive activity at the termination of the episode. All had normal initial electroencephalogram's (EEG) and one had centrotemporal spikes on his EEG when repeated at age 6 years. Anticonvulsant therapy resulted in a reduced frequency of breath-holding spells. The epidemiology, pathophysiology and therapy of breath-holding spells is discussed with reference to this unique family. This report gives further credence to the notion that there often may be a familial predisposition to breath-holding spells.

Hb-M "Hyde Park": a de novo mutation, identified by mass spectrometry and DNA analysis

BACKGROUND

Structural hemoglobinopathies usually are inherited as autosomic dominant traits; de novo mutations are uncommon. Analytical and preparative procedures for the characterization of an abnormal hemoglobin are complex and time-consuming. Mass spectrometer analysis allows a rapid identification of the amino acid substitution.

METHODS AND RESULTS

A cyanotic 7-year-old girl was found to have 16% methemoglobin. Laboratory data showed the presence of an abnormal hemoglobin, which was isolated by collecting the abnormal peak from DEAE and globin chains from CM52. The amino acid substitution was rapidly identified by FAB mass spectroscopic analysis, leading to the recognition of HbM Hyde Park. These data were confirmed by molecular analysis (Southern blot and DNA sequencing). Neither the parents nor a sister showed any abnormality; non-paternity was excluded by blood group serology and HLA typing.

CONCLUSIONS

This is a case of HbM Hyde-Park arising as a de novo mutation. FAB mass spectroscopic analysis is a rapid and useful analytical method for identifying aminoacid substitution.

A second observation of the fetal methemoglobin variant Hb F-M-Fort Ripley or alpha 2G gamma 2(92)(F8)His----Tyr

We have identified a second baby with the fetal methemoglobin F-M-Fort Ripley. It was observed in a Caucasian infant from Canada; at least eleven additional members of that family were known to have had a neonatal cyanosis similar to that seen in the propositus and in a previously described baby (2). Sequencing of amplified DNA that included (part of) the G gamma gene greatly facilitated the characterization. The G gamma X chain was readily isolated by reversed phase high performance liquid chromatography; its quantity was approximately 12.5% of total gamma. Interestingly, the baby also carried the A gamma T mutation on one chromosome, either in cis or in trans to the G gamma X mutation. Hb F-M-Fort Ripley could be isolated in reasonably pure form by DEAE-cellulose chromatography. The isolated Hb FX was unstable, had spectral changes characteristic for the M-hemoglobins, while its methemoglobin derivative reacted rapidly with cyanide. Oxygen affinity data could not be obtained. It is suggested that the formation of a rather large amount (approximately 25%) of mixed hybrids (alpha 2G gamma X.gamma) with low oxygen affinity is the main cause for the occurrence of the neonatal cyanosis.

[Oxygen-binding properties of blood in hemoglobinosis M Boston detected in the USSR for the first time]

Hemoglobin M-Boston comprising 30% of the total blood Hb was detected in two members of a Russian family. The stages of its identification were described. An analysis was made of probands' whole blood oxy-Hb dissociation curves. At pO2 = 100 mm Hg oxygenation of Hb M-Boston beta-chains was 44% only, while mutant alpha-chains were completely oxidated. Despite a significant decrease in arterial blood oxygen content arteriovenous variation by O2 content at pO2 differential from 100 to 40 mm Hg is within the normal level due to various directions of changes in P50 and Hill's coefficient of probands' whole blood. The authors consider that pronounced cyanosis in Hb M-Boston carriers is not the consequence of tissue hypoxia but is caused by a higher content of nonfunctioning Hb M-Boston that changes the blood color.

[Hereditary cyanosis caused by the presence of abnormal hemoglobin M in the blood: its detection, identification and properties]

A total of 17 cases of anomalous hemoglobin M (Hb M) were detected among subjects of varying nationalities in different regions of the USSR. The methods used for identification of Hb M Saskatoon, Hb M Boston, Hb M Iwate, Hb M Hyde Park have been described, among them--electron paramagnetic resonance. Spectral characteristics, electrophoretic mobility of these Hb in pH gradient, reaction with cyanides, thermal stability, in vitro reduction with methemoglobin reductase, isolated from donor's red blood cells, have been investigated. The functional parameters (log P50 and n) have been determined for hemolysates containing anomalous hemoglobin, as well as for chromatographically pure fractions of anomalous hemoglobins. The importance of the proper diagnosis of hemoglobinosis M has been stressed.

Hb Warsaw (beta 42 Phe----Val): an unstable hemoglobin with decreased oxygen affinity. I. Hematologic and clinical expression

Four members in two generations of a Polish-American family exhibited findings of congenital Heinz-body hemolytic anemia accompanied by cyanosis. Two of the affected family members have also developed severe pulmonary hypertension, with a fatal outcome in one of them. Blood from the affected individuals showed decreased oxygen affinity and contained elevated levels of methemoglobin. An unstable hemoglobin fraction underwent rapid precipitation following exposure of the red cell lysates to isopropyl alcohol or heat. This hemoglobin contained a newly identified abnormal beta chain with an amino acid substitution at the same position as that of Hb Hammersmith and Hb Bucuresti-Louisville.

Mutant fetal hemoglobin causing cyanosis in a newborn

A well but cyanotic newborn was found to have a mutant gamma-globin chain, leading to a functionally abnormal fetal hemoglobin. A single amino acid substitution was found in a site consistent with known adult M hemoglobins. This patient showed no clinical evidence of cyanosis at 5 weeks of age as gamma-chain synthesis was replaced by beta-chain synthesis. A sibling born 20 months later was also cyanotic and the same mutant hemoglobin was found.

Studies of nicotinamide adenine dinucleotide methemoglobin reductase activity in a Jewish population

In the original study of the deleterious effects of oxidant drugs on persons heterozygous for nicotinamide adenine dinucleotide reductase (NADH MetHb R) deficiency, several Jewish physicians used as controls had decreased enzyme activity. We collected blood samples from 555 Jewish persons to 1) estimate the heterozygote frequency for NADH MetHb R deficiency; and 2) determine if external variables such as age, gender, and ingested medications may alter the NADH MetHb R activity and thereby alter estimates of heterozygosity. Two persons possibly heterozygous for the deficiency were identified (carrier incidence = 1/309,000 jewish births). A difference in enzyme activity was found between males and females (P less than 0.03). We have examined the influence of the mean red cell age on the activity of erythrocyte NADH MetHb R and found it not to be materially influenced by mean red cell age; thus the possible intersex differences of mean red cell age cannot explain this observation. No significant difference (P greater than 0.1) was seen between persons ingesting the following drugs and those not: Dilantin; antidepressants/sedatives; cardiac, antineoplastic, or antigout/antiinflammatory drugs; thyroid supplements, estrogen-containing preparations, and antihistamines. NADH MetHb R activity did not correlate with age or spontaneous abortion. We conclude that heterozygosity for NADH MetHb R deficiency is not prevalent among Ashkenazic Jewish persons, and that external variables should be considered to ensure accurate interpretation of NADH MetHb R activity for correct estimation of heterozygosity.

Haemoglobin Miwate in Cape Town: A report of 2 cases

Two siblings had suffered from cyanosis since birth owing to the presence of Hb MIwate. The diagnosis was confirmed by electrophoresis, spectroscopy and peptide analysis. The benign nature of this unusual condition is stressed.

Hemoglobin Beth Israel. A mutant causing clinically apparent cyanosis

We found that an abnormal hemoglobin with a very low oxygen affinity was responsible for overt cyanosis in an otherwise healthy adolescent. Hemoglobin Beth Israel, in which serine replaces the asparagine residue normally present at position 102 (G4) of the beta-polypeptide chain, was associated with normal blood counts and no apparent exercise intolerance in the heterozygous carrier. Cyanosis resulted from a drastically right-shifted oxygen dissociation curve, whose position and shape could account for the absence of "physiologic" anemia. The whole-blood oxygen tension at 50 per cent oxygen saturation was 88 mm Hg (normally 26 +/- 1 mm Hg), and the arterial blood was only 63 per cent saturated with oxygen despite a normal oxygen tension of 97 mm Hg. The hemolysate showed a low oxygen affinity but normal Bohr effect. Unexplained cyanosis, particularly in association with normal arterial oxygen tension should prompt a search for an abnormal hemoglobin, which may obviate the need for invasive diagnostic procedures.

A study on the biochemical genetics of abnormal hemoglobins

In recent years, there were found in China 2 kinds of hemoglobin-M (Hb M Shanghai-1, Hb M Shanghai-2) and 2 kinds of unstable hemoglobin (Hb Shanghai-1, Hb Shanghai-2), amoung which the propositus of Hb Shanghai-2 proved to be a heterozygote for both unstable hemoglobin gene and beta-thalassaemia gene. This article gives an account of the biochemical analysis and genetic studies of these four kinds of abnormal homoglobins. Besides, we present here also the records of 2 family pedigrees of alpha-thalassaemia, and found in the blood of a patient a small quantity of another abnormal hemoglobin constituent in addition to Bart's hemoglobin and hemoglobin H. On these bases, a new hypothesis concerning the heredity of alpha-thalassaemia disease is proposed.