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Abstract
Methemoglobinemia is a condition characterized by the presence of high concentrations of methemoglobin in blood, which is unable to release oxygen to the tissues. It is a rare entity, with low diagnostic suspicion, and can be acquired or hereditary. Among the hereditary forms, there are hemoglobin M and congenital recessive methemoglobinemia. The latter is caused by a deficiency of the enzyme NADH cytochrome b5 reductase (B5R), as a consequence of biallelic alterations in the CYBR3 gene. We report the clinical, hematologic and molecular characteristics of a newborn with a diagnosis of B5R deficiency.
The infant presented with cyanosis in the first hours of life and elevated methemoglobin levels. After ruling out pulmonary, cardiac, infectious and other acquired causes, the diagnosis was reached by CYB5R3
gene sequencing. We emphasize the importance of recognizing the cause of methemoglobinemia in order to provide adequate treatment and genetic counseling.
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