RESUMEN
Neonatal cyanosis in healthy newborns can be associated either with methemoglobin due to cytochrome b5 reductase deficiency or to M-hemoglobin, a group of hemoglobin variants resulting from mutations in the globin chain genes. We report the clinical case of a neonate with cyanosis and normal cardiac and respiratory function. At birth the hematological parameters were normal; however, the methemoglobinemia was 16%. Spontaneously, the cyanosis gradually decreased and by the fifth month of age the methemoglobin level was normal. A heterozygous Gγ-globin gene (HBG2) missense mutation 87 C-A (Leu28Met) was identified. His father, with a history of transfusion in the neonatal period, is heterozygous for the same mutation. This hemoglobin variant, not previously described, was called Hb F Viseu and is the sixth Gγ-chain variant reported in association with neonatal cyanosis.