An unusual cause of neonatal cyanosis…

Abstract

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.

Methemoglobinemia in a Newborn

“…Methaemoglobinaemia should be suspected in newborns, in the absence of any obvious cardiac and pulmonary dysfunction that are persistent cyanosis and hypoxia and did not improve in the administration of oxygen supplementation. [1][2][3] In methaemoglobinaemia, the haeme iron is oxidised to the ferric (Fe 3+ ) rather than ferrous (Fe 2+ ). [1][2][3][4][5] The ferric haeme in methaemoglobin is unable to neither bind nor transport oxygen.…”

“…[1][2][3] In methaemoglobinaemia, the haeme iron is oxidised to the ferric (Fe 3+ ) rather than ferrous (Fe 2+ ). [1][2][3][4][5] The ferric haeme in methaemoglobin is unable to neither bind nor transport oxygen. These reduce the affinity of haemoglobin to oxygen and shift the curve to the left leading to tissue hypoxia and acidosis.…”

“…These reduce the affinity of haemoglobin to oxygen and shift the curve to the left leading to tissue hypoxia and acidosis. [1][2][3]5 Methaemoglobinaemia is a rare disease that occur when the red blood cells contain methaemoglobin at levels higher than 1%. 1,6 Methaemoglobinaemia has two forms; inherited and acquired.…”

“…1,6 Methaemoglobinaemia has two forms; inherited and acquired. 2 Inherited disorder causing methaemoglobinaemia resulted from an enzymatic deficiency of Nicotinamide adenine dinucleotide cytochrome b5 reductase, 1,2,5 which is classified into two distinct phenotypes. In type I, the most common form, the deficiency of NADH cytochrome b5 activity is found only in erythrocytes, with other cell types unaffected.…”

“…Cyanosis can also be caused by a reduced blood oxygen carrying capacity secondary to an abnormal form of haemoglobin, such as methaemoglobinaemia. 1,2…”