HbM methaemoglobinaemia as a rare case of early neonatal benign cyanosis.

Early neonatal central cyanosis that is unrelated to cardiopulmonary causes, alerts clinicians to possibility of methaemoglobinaemia. Congenital methaemoglobinaemia due to haemoglobin M is an autosomal dominant disorder characterised by lifelong cyanosis. We report a case presentation and review of diagnostic pitfalls of a newborn who presented with central cyanosis; investigations revealed a low methaemoglobin reductase (2.2 IU/g Hb), with normal maternal levels (9.1 IU/g Hb). Therefore, haemoglobinopathy investigations were completed on the mother and her baby, which showed an α-globin variant in both. The maternal α2 globin gene sequencing showed heterozygosity for haemoglobin M Boston (α58 His → Tyr).