Hemoglobin M Disease as a Cause of Cyanosis in a Newborn

Congenital Methemoglobinemia: First Confirmed Case in the Arab Population with a Novel Variant in the CYB5R Gene in the State of Qatar: A Case Report

Methemoglobinemia (MetHb) is a rare hematological condition characterized by high methemoglobin levels in the blood. It happens when hemoglobin is oxidized, resulting in hypoxia and cyanosis, which may occur in inherited or acquired forms. Inherited or congenital methemoglobinemia is a rare autosomal recessive condition and has never been reported in the Arab population. Here we report a case of a 22-year-old Arab man with a positive family history who presented with bluish discoloration of the fingers and lips and was found to have methemoglobinemia. Genetic study on the patient and his family revealed compound heterozygous variants in the CYB5R3 Exon 5 c.431G>A p.Gly144Asp likely pathogenic variant and CYB5R3 Exon 9 c.871G>A p.Val291Met variant of unknown significance. We suggest that the novel c.871G>A p.Val291Met variant could be causative for methemoglobinemia.

A Case of Congenital Methemoglobinemia: Rare but Real

Methemoglobin (MetHb) is a form of hemoglobin in which iron in Hb is in an oxidized form (ferric) instead of ferrous, making it difficult to bind with oxygen. Usually, MetHb is present in small quantities (<1%) in humans, but once MetHb increases beyond 3%, the condition is known as methemoglobinemia. It can be further classified into hereditary and acquired. Hereditary forms are a rare cause of hypoxia and cyanosis. Only a few cases have been reported worldwide. Here, we present a case of a 33-year-old female with congenital methemoglobinemia who remains relatively healthy in spite of her underlying condition. This case report focuses on knowledge sharing and practical aspects of managing patients with congenital methemoglobinemia.

Acquired methemoglobinemia presenting to the pediatric emergency department: a clinical challenge

OBJECTIVES

Acquired methemoglobinemia (MetHb) is an uncommon presentation of cyanosis in the pediatric emergency department (ED), making its diagnosis and management a clinical challenge. Through this case series we hope to improve clinician ability to recognize the potential for MetHb in pediatric ED patients and to avoid overlooking this important cause of cyanosis.

METHODS

This was a case series using a health records review, investigating patients diagnosed with MetHb at our pediatric ED during 2007-2018. We included only cases with methemoglobin saturation ≥5%.

RESULTS

Ten patients were diagnosed with MetHb in our pediatric ED during the study period. Five had an underlying hematologic disease who received a pharmacologic trigger known to induce MetHb as well (four dapsone, one rasburicase). The other five patients were previously healthy, who presented with a clinical picture of hemolytic anemia, all of whom were diagnosed with previously unknown glucose-6-phosphate dehydrogenase (G6PD) deficiency. Two of the patients received methylene blue, and five patients needed packed red blood cells. All of the patients survived the acute MetHb episode.

CONCLUSION

Acquired MetHb in the pediatric ED is a rare but important cause of cyanosis. Diagnosis and management of acute, acquired MetHb in the ED requires a high level of suspicion, and a background knowledge of the common precipitants and underlying conditions associated with this condition. We hope this case series will help ED physicians to consider MetHb in pediatric patients presenting with cyanosis and persistent hypoxia. Exposure to known precipitants (e.g., medications and foods), particularly in the setting of active treatment for malignancy or with symptoms of hemolytic anemia should further increase suspicion.

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.