Hereditary Congenital Methemoglobinemia Diagnosed at the Age of 79 Years: A Case Report.

Background: Cardiopulmonary disorders are the most common cause of central cyanosis, and methemoglobinemia is often overlooked in the differential diagnosis of patients with central cyanosis. In most cases, methemoglobinemia is acquired and hereditary congenital methemoglobinemia is rare. Only a few case reports of congenital methemoglobinemia can be found in PubMed. To date, only four cases of congenital methemoglobinemia diagnosed after the age of 50 years have been reported. Case Presentation: A 79-year-old Japanese woman presented at our hospital with the chief complaints of dyspnea and cyanosis. She exhibited cyanosis of the lips and extremities, and her SpO2 was 80%, with oxygen administration at 5 L/min. Blood gas analysis revealed a PaO2 of 325.4 mmHg and methemoglobin level of 36.9%. The SpO2 and PaO2 values were dissociated, and methemoglobin levels were markedly elevated. Genetic analysis revealed a nonsynonymous variant in the gene encoding nicotinamide adenine dinucleotide cytochrome (NADH) B5 reductase 3 (CYB5R3), and the patient was diagnosed with congenital methemoglobinemia. Conclusions: It is important to consider methemoglobinemia in the differential diagnosis of patients with central cyanosis. At 79 years of age, our patient represents the oldest patient with this diagnosis. This report indicates that it is crucial to consider the possibility of methemoglobinemia regardless of the patient's age.

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.

CYB5R3 homozygous pathogenic variant as a rare cause of cyanosis in the newborn.

Detailed below is a very illustrative case of a rare pathology of recessive congenital methemoglobinemia. The patient, a newborn female, was homozygous for c.535G > A, p.(Ala179Thr) a pathogenic variant in the CYB5R3 gene. The reported population frequency of the allele is 0.853%, demonstrating why it is remarkable to find both parents are heterozygous carriers without consanguinity. A brief review of previously published cases is also presented.

Cyanosis, hemolysis, decreased HbA1c and abnormal co-oximetry in a patient with hemoglobin M Saskatoon [HBB:c.190C > T p.His64Tyr].

We describe a first Dutch case of Hb M Saskatoon (HBB:c.190C > T p.His64Tyr) in a 47-year-old female Dutch patient who presented with cyanosis, hemolysis, and abnormal co-oximetry. A mean corpuscular volume (MCV) of 105 fL caused by reticulocytosis (160 × 109/L) and low red blood cell count (3.6 × 1012/L) suggested an increased erythrocyte turnover. An HPLC glyco-globin analysis revealed a decreased HbA1c fraction of 12.3 mmol/mmol, HbA0 of 93.3% and an additional unidentified fraction at 1.2 min. DNA sequencing revealed a missense mutation in the HBB gene, (HBB:c.190C > T p.His64Tyr), known as Hb M Saskatoon, a variant which has been previously identified as an unstable hemoglobin variant leading to methemoglobinemia and anemia. In this report, we describe the clinical and remarkable laboratory aspects of our patient with Hb M Saskatoon, and the consequences for treatment and drug use.

Interpreting sulfhemoglobin and methemoglobin in patients with cyanosis: An overview of patients with M-hemoglobin variants.

INTRODUCTION: Methemoglobin (MetHb) and sulfhemoglobin (SHb) measurements are useful in the evaluation of cyanosis. When one or both values are elevated, additional analysis is important to establish the etiology of the disorder. Methemoglobinemia occurs from acquired or hereditary causes with diverse treatment considerations, while true sulfhemoglobinemia is only acquired and treatment is restricted to toxin removal. Some toxic exposures can result in a dual increase in MetHb and SHb. Hereditary conditions, such as M-Hemoglobin variants (M-Hbs), can result in increased MetHb and/or SHb values but are clinically compensated and do not require treatment if they are cyanotic but otherwise clinically well. METHODS: Herein, we report 53 hemoglobin variant cases that have associated MetHb and SHb levels measured by an adapted Evelyn-Malloy laboratory assay method. RESULTS: Our data indicate M-Hbs cause variable patterns of MetHb and SHb elevation in a fairly reproducible pattern for the particular variant. In particular, α globin chain M-Hbs can mimic acquired sulfhemoglobinemia due to an isolated increased SHb value. CONCLUSION: If the patient appears clinically well other than cyanosis, M-Hbs should be considered early in the evaluation process to differentiate from acquired conditions to avoid unnecessary testing and treatment regimens and prompt genetic counseling.

Chronic perinatal hypoxia delays cardiac maturation in a mouse model for cyanotic congenital heart disease.

Compared with acyanotic congenital heart disease (CHD), cyanotic CHD has an increased risk of lifelong mortality and morbidity. These adverse outcomes may be attributed to delayed cardiomyocyte maturation, since the transition from a hypoxic fetal milieu to oxygen-rich postnatal environment is disrupted. We established a rodent model to replicate hypoxic myocardial conditions spanning perinatal development, and tested the hypothesis that chronic hypoxia impairs cardiac development. Pregnant mice were housed in hypoxia beginning at embryonic day 16. Pups stayed in hypoxia until postnatal day (P)8 when cardiac development is nearly complete. Global gene expression was quantified at P8 and at P30, after recovering in normoxia. Phenotypic testing included electrocardiogram, echocardiogram, and ex vivo electrophysiology study. Hypoxic P8 animals were 47% smaller than controls with preserved heart size. Gene expression was grossly altered by hypoxia at P8 (1,427 genes affected), but normalized after recovery (P30). Electrocardiograms revealed bradycardia and slowed conduction velocity in hypoxic animals at P8, with noticeable resolution after recovery (P30). Notable differences that persisted after recovery (P30) included a 65% prolongation in ventricular effective refractory period, sinus node dysfunction, 23% reduction in ejection fraction, and 16% reduction in fractional shortening in animals exposed to hypoxia. We investigated the impact of chronic hypoxia on the developing heart. Perinatal hypoxia was associated with changes in gene expression and cardiac function. Persistent changes to the electrophysiological substrate and contractile function warrant further investigation and may contribute to adverse outcomes observed in the cyanotic CHD population.NEW & NOTEWORTHY We utilized a new mouse model of chronic perinatal hypoxia to simulate the hypoxic myocardial conditions present in cyanotic congenital heart disease. Hypoxia caused numerous abnormalities in cardiomyocyte gene expression, the electrophysiologic substrate of the heart, and contractile function. Taken together, alterations observed in the neonatal period suggest delayed cardiac development immediately following hypoxia.

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.

IDDCA syndrome in a Chinese infant due to GNB5 biallelic mutations.

Herein, we present a Chinese infant with an early-onset intellectual developmental disorder with cardiac arrhythmia syndrome. A 6-month-old boy visited our hospital because of convulsions and paroxysmal cyanosis for 1 day. Mental development analysis showed that the patient had a neurodevelopmental delay. Frequent seizures occurred, and ECG monitoring demonstrated severe cardiac arrhythmia. Whole-exome sequencing showed that the infant had two compound heterozygous variants, NM_016194:c.458G>A/p.Cys153Tyr and NM_016194:c.1032C>A/p.Tyr344*, in GNB5. The first variant was inherited from his mother, while the other one was a de novo variant. Haplotype analysis indicated that the de novo variant was located in the paternal chromosome. Structural modeling indicated that both mutations could influence the interaction of GNB5 with its binding protein. Our study expanded the known genetic and phenotypic spectrum of GNB5-associated diseases, by presenting a Chinese male infant with IDDCA.

Exon sequencing of the alpha-2-globin gene for the differential diagnosis of central cyanosis in newborns: a case report.

BACKGROUND: Cyanosis is usually associated with serious conditions requiring urgent treatment in the neonatal intensive care unit (NICU). Hemoglobin M (Hb M) disease is one type of congenital methemoglobinemia characterized by cyanosis. Among these variants, α-globin chain mutations such as Hb M Boston present cyanosis from birth while other variants usually manifest later in life. CASE PRESENTATION: We report a case of a male newborn with cyanosis apparent since birth. Surprisingly, his respiratory and hemodynamic status including normal arterial blood oxygen saturation was stable, but oxygen saturation on pulse oximetry did not increase after 100% supplemental oxygen was started. In addition to routine pulmonary and cardiologic evaluation, further evaluation for dyshemoglobin was conducted; α2-globin gene sequencing showed a single-point variant causing Hb M Boston. Methemoglobin (MetHb) level estimated by co-oximetry was normal. After a 14-day stay in the NICU, the patient remained respiratory and hemodynamically stable without supplemental oxygen except for cyanosis. CONCLUSIONS: Hb M disease is a benign disease and does not require any treatment whereas acquired methemoglobinemia is a potentially fatal condition. Neonatologists should be aware that low oxygenation status on pulse oximetry in the face of normal arterial blood saturation values might indicate the possibility of Hb M disease in early neonatal cyanosis, irrespective of MetHb value.

Downregulation of microRNA­199a­5p protects cardiomyocytes in cyanotic congenital heart disease by attenuating endoplasmic reticulum stress.

Chronic hypoxia is a key pathological change in patients with cyanotic congenital heart defect (CCHD). It has been demonstrated that enhanced myocardial unfolded protein response (UPR) increases the capacity to buffer endoplasmic reticulum (ER) stress and to avoid subsequent apoptosis caused by the hypoxia that underlies CCHD. The present study was performed to determine the regulatory role of microRNAs (miRNAs) in this cytoprotective UPR process. The results revealed that miR­199a­5p was markedly downregulated in the cardiac tissue of patients with CCHD and in human myocardial cells cultured in hypoxic conditions. The two major UPR modulators, 78 kDa glucose­regulated protein (GRP78) and activating transcription factor 6 (ATF6), were potential target genes of miR­199a­5p in CCHD myocardial specimens. In addition, the miR­199a­5p mimic and inhibitor were evidently able to change GRP78 and ATF6 gene expression and ER stress­associated apoptosis in hypoxia­treated cardiomyocytes. The interaction between miR­199a­5p and the ATF6 and GRP78 3'­UTR binding sites in myocardial cells was also confirmed by luciferase assay. Thus, it is concluded that myocardial downregulation of miR­199a­5p favors the UPR against hypoxia­induced ER stress in CCHD, which contributes to myocardial protection.

Detection of Hb Rothschild HBB: c.[112T>A or 112T>C], Through High Index of Suspicion on Abnormal Pulse Oximetry.

We describe a case with a low oxygen affinity hemoglobin (Hb) variant who presented with cyanosis in the absence of cardiopulmonary disease. The patient, a 27-year-old pregnant female (P1G2), complained of a productive cough and bluish discoloration of the lips that started 3 days prior to seeking attention. She had no previous episodes and has generally been in good health. A positive family history of cyanosis was obtained in one sibling. Systematic examination, notably the cardiorespiratory system, revealed no abnormalities. The arterial Hb oxygen saturation (SpO2) on pulse oximetry was 81.0% and Hb separation studies revealed an Hb variant identified as Hb Rothschild [ß37(C3)Trp→Arg] (HBB: c.[112 T>A or 112 T>C]) by gene sequencing. The amino acid substitution (Trp→Arg) is an important contact point at the α1ß2 interface and favors a T-quaternary state of the Hb tetramer. This leads to a low oxygen affinity state, which results in premature release of oxygen and drop in oxygen saturation. In the absence of cardiopulmonary disease, a decreased oxygen saturation reading, with or without cyanosis, should arouse suspicion for a possible dysHb.

Neonatal Cyanosis Due to Hemoglobin Variant: Hb F-Sarajevo.

Neonatal cyanosis is rarely due to hemoglobin variants with low oxygen affinity. We describe the clinical course and results of molecular genetic analysis of a boy who presented after birth with severe cyanosis. Arterial blood-gas analysis demonstrated a pronounced shift of the oxygen-hemoglobin dissociation curve to the right and molecular genetic analysis revealed a γ-globin variant, Hb F-Sarajevo. The patient presented is the second reported case of neonatal cyanosis due to this mutation, which was first described in 2012 by Zimmermann-Baer and coauthors. With the introduction of universal screening for congenital heart disease, the finding of low oxygen saturation will uncover more neonates with hemoglobinopathies with low oxygen affinity.

Diagnosis of a rare fetal haemoglobinopathy in the age of next-generation sequencing.

Neonatal cyanosis resulting from a fetal methaemoglobin variant is rare. Most such variants are only described in a few published case reports. We present the case of a newborn with unexplained persistent cyanosis, ultimately determined to have a γ-chain mutation causing Hb FM-Fort Ripley. This neonatal haemoglobinopathy can be challenging to diagnose, as significant oxygen desaturation may result from barely detectable levels of the mutant haemoglobin and co-oximetry studies may show a falsely normal methaemoglobin level. Our analysis of the infant's haemoglobin included high-performance liquid chromatography, cellulose acetate electrophoresis and citrate agar electrophoresis, which showed trace amounts of a suspected variant. Ultimately, the diagnosis was made through a novel application of next-generation sequencing (NGS). NGS-based diagnostic approaches are becoming increasingly available to clinicians, and our case provides a framework and evidence for the utilisation of such testing paradigms in the diagnosis of a rare cause of neonatal cyanosis.

Congenital methemoglobinaemia due to Hb F-M-Fort Ripley in a preterm newborn.

Methemoglobinaemia is a rare cause of cyanosis in newborns. Congenital methemoglobinaemias due to M haemoglobin or deficiency of cytochrome b5 reductase are even rarer. We present a case of congenital methemoglobinaemia presenting at birth in a preterm infant. A baby boy born at 29 weeks and 3 days of gestation had persistent central cyanosis immediately after delivery, not attributable to a respiratory or cardiac pathology. Laboratory methemoglobin levels were not diagnostic. Cytochrome b5 reductase levels were normal and a newborn screen was unable to pick up any abnormal variants of fetal haemoglobin. Genetic testing showed a γ globin gene mutation resulting in the M haemoglobin, called Hb F-M-Fort Ripley. The baby had no apparent cyanosis at a corrected gestational age of 42 weeks. Although rare, congenital methaemoglobin aemia should be considered in the differential in a preterm with central cyanosis and investigated with genetic testing for γ globin chain mutations if other laboratory tests are non-conclusive.

[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 ß2 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.

Hb M-Iwate in an Indian family.

BACKGROUND: High performance liquid chromatography in a newborn girl with congenital cyanosis and a unilateral cleft palate revealed a variant hemoglobin with retention time of 4.8 min, similar to hemoglobin Q-India. Since hemoglobin Q-India did not explain the cyanosis, further investigations were initiated. METHODS: Sequencing of α-globin genes revealed hemoglobin M-Iwate ([α87 (F8) His → Tyr]) that was confirmed on restriction enzyme analysis. RESULTS: Hemoglobin M-Iwate is a rare methemoglobinemic variant formed due to a point mutation in the α-globin gene. Primarily reported from the Iwate prefecture of Japan, there have been occasional case reports from other regions as well. Inherited methemoglobinemia finds only rare mention in Indian literature while hemoglobin M-Iwate has not been reported from India. CONCLUSIONS: This case illustrates the step-wise logical diagnostic approaches necessary to elucidate the cause of methemoglobinemia in an otherwise healthy child with cyanosis.

Novel FBN1 gene mutation and maternal germinal mosaicism as the cause of neonatal form of Marfan syndrome.

Marfan syndrome (MFS) is an autosomal dominant disorder caused by mutations in the fibrillin 1 gene (FBN1). Neonatal form of MFS is rare and is associated with severe phenotype and a poor prognosis. We report on a newborn girl with neonatal MFS who displayed cyanosis and dyspnea on the first day of life. The main clinical features included mitral and tricuspid valve insufficiency, aortic root dilatation, arachnodactyly, and loose skin. Despite the presence of severe and inoperable heart anomalies, the girl was quite stable on symptomatic treatment and lived up to the 7th month of age when she died due to cardiorespiratory failure. Molecular-genetic studies revealed a novel intronic c.4211-32_-13del mutation in the FBN1 gene. Subsequent in vitro splicing analysis showed this mutation led to exon 35 skipping, presumably resulting in a deletion of 42 amino acids (p.Leu1405_Asp1446del). Interestingly, this mutation is localized outside the region of exons 24-32, whose mutation is responsible for the substantial majority of cases of neonatal MFS. Although the family history of MFS was negative, the subsequent molecular genetic examination documented a mosaicism of the same mutation in the maternal blood cells (10-25% of genomic DNA) and the detailed clinical examination showed unilateral lens ectopy.