Transient neonatal cyanosis associated with a new Hb F variant: Hb F viseu

The first Chinese with Hb Chile leading to chronic anemia and methemoglobinemia: a case report

BACKGROUND

Hemoglobin (Hb) Chile [β28(B10) Leu > Met; HBB: c.85 C > A] is a rare hemoglobin variant caused by a missense mutation in the HBB gene. Only one case of Hb Chile has been reported worldwide so far. It is an unstable hemoglobin, characterized by cyanosis associated with chronic methemoglobinemia and hemolytic anemia induced by sulfonamides or methylene blue.

CASE PRESENTATION

A 9-year-3-month-old girl had mild anemia of unknown etiology for more than 6 years. She had a slight pallor without other symptoms or signs. The complete blood count revealed normocytic normochromic anemia with a sometimes-elevated reticulocyte count, and the bone marrow cytology showed marked erythroid hyperplasia, but the tests related to hemolysis were normal. Therefore, the whole exome sequencing was performed and showed a heterozygous mutation for HBB: c.85 C > A. With asymptomatic methemoglobinemia confirmed later, she was eventually diagnosed with Hb Chile.

CONCLUSIONS

This is the first report of Hb Chile in China and the second worldwide. This case shows that Hb Chile is clinically heterogeneous and difficult to diagnose and expands our understanding on the clinical and hematological traits of the disease.

The journey from blue to pink–a rare cause for self-limiting methemoglobinemia in an Indian baby

Objectives

To describe a rare case of methemoglobinemia in a newborn baby with excellent prognosis. Methemoglobinemia in the neonatal period is very rare and when present is usually caused by environmental toxicity from strong oxidizing agents and rarely due to enzyme deficiency or inherited disorders of hemoglobin metabolism.

Case presentation

We report a newborn baby presented with cyanosis and desaturation right from birth, later found to have methemoglobinemia and started medication. Genetic evaluation revealed a mutation in the gamma chain of fetal haemoglobin (HbF) causing abnormal hemoglobin. Physiologically significant mutations in gamma-globin genes cause symptoms in the fetus and neonate that gradually abate in the first few months of life.

Conclusions

Genetic evaluation is advisable in babies with unexplained methemoglobinemia as the prognosis of the condition depends on the underlying mutation. Early diagnosis of methemoglobinemia due to gamma chain mutation in HbF as in our case helps in reassuring the parents and also in preventing unnecessary aggressive investigations.

Clinical characteristics on manifestation and gene mutation of a transient neonatal cyanosis: A case report

BACKGROUND

We analyzed the main features of an infant diagnosed with temporary neonatal cyanosis in order to strengthen our understanding of the disease.

CASE SUMMARY

We report a patient diagnosed with temporary neonatal cyanosis. The main clinical characteristics, gene mutation and treatment are discussed and a review of related literature was conducted. The neonate aged 1 d and 5 h was admitted to hospital due to cyanosis after birth. The main clinical manifestation was cyanosis, which was not improved by auxiliary ventilation and the patient showed no obvious shortness of breath or methemoglobinemia. Gene mutation analysis showed a heterozygous c.190C>T mutation in the HBG2 gene associated with transient neonatal cyanosis, which was derived from his mother. Symptomatic supportive treatment was given for 2 mo. The neonate was discharged and gradually improved with oral administration of vitamin C and vitamin B2 for 2 wk.

CONCLUSION

There is no special treatment for temporary neonatal cyanosis caused by heterozygous mutation of the HBG2 gene.

Failing blood gas measurement due to methemoglobin forming hemoglobin variants: a case report and review of the literature

INTRODUCTION

We present a case of an arterial blood gas sample analysis from a 33-year old woman where no oximetry results could be obtained using the Radiometer ABL800 FLEX device. Clinical history of this patient learned that she was carrier of a methemoglobin forming hemoglobin variant type Hyde Park (HbM Hyde Park) and raised the question whether or not this variant could be the cause of the errors obtained during analysis.

MATERIALS AND METHODS

A literature search was performed, focusing on methemoglobin forming hemoglobin variants and their influence on oxygenation measurements. An overview of the currently described methemoglobin forming hemoglobin variants is also included.

RESULTS AND DISCUSSION

In the presence of dyshemoglobins such as methemoglobin, techniques used to obtain parameters that reflect the patient oxygenation status, such as pulse oximetry and CO-oximetry can be influenced. In these cases, CO-oximetry is the preferred technique because it can compensate for this, in contrast to pulse oximetry. In case of the presence of methemoglobin originating from a hemoglobin variant, it is possible that CO-oximetry data cannot be calculated because the absorbance spectrum of this methemoglobin can differ from regular methemoglobin. Moreover, pulse oximetry devices are actually prone to erroneous results since pulse oximetry data will be calculated in these cases, but unreliable and should be avoided.

CONCLUSION

Methemoglobin forming hemoglobin variants are rare genetic mutations. However, they can possibly interfere with the calculation of CO-oximetry values. In these cases, pulse oximetry data should be avoided because they could lead to incorrect medical decisions.

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.

An unusual cause of neonatal cyanosis…

We report a case of a female neonate whose pulse oximetry screening for congenital heart disease at 40 h of life was positive. The pregnancy was uneventful with no relevant family history. The neonate presented with bluish discolouration of the skin lasting until day 15. Cardiovascular examination and chest radiography were normal. Septic screening was negative. Oxygen therapy was started with poor response; investigations revealed a methaemoglobinaemia of 7.4%. The methaemoglobin level reached a peak of 15% on day 10, falling thereafter. The infant was discharged by day 20 with a normal physical examination and a methaemoglobinaemia of 11.4%. By 2 months of age this had fallen to 2.4%. Further investigation revealed a haemoglobin M variant: a heterozygous mutation of the γ globin gene known as Hb F-M Viseu. The mutation occurs in the γ chain, therefore the methaemoglobinaemia is transitory, resolving with the transition from fetal to adult haemoglobin.

Diagnosis and prevention of thalassemia

Thalassemia is the most common monogenic inherited disease worldwide and it affects most countries to various extents. This review summarizes the current approaches to phenotypic and genotypic diagnosis of thalassemia in clinical practice. Prevention strategies that encompass carrier screening, genetic counseling and prenatal diagnosis are discussed. The importance of public education and an awareness of a changing perception regarding this group of diseases are emphasized. It also addresses the impact of the rapidly increasing knowledge in disease severity modification by hemoglobin F (Hb F).