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Congenital methemoglobinemia is a rare cause of cyanosis that is characterized by increased methemoglobin levels and caused by mutations in the cytochrome B5 reductase 3 (CYB5R3) gene resulting in deficiencies of the nicotinamide adenine dinucleotide-cytochrome b5 reductase enzyme. The congenital disease has two types: type I, in which the enzyme deficiency occurs only in the erythrocytes, and type II, in which all tissues are affected. Accordingly, cyanosis is the sole clinical manifestation in type I, whereas cyanosis is accompanied by such severe neurological findings as intellectual disability, microcephaly, generalized dystonia, and movement disorders. In this study, a case who presented with respiratory distress was found to have high methemoglobin levels and was diagnosed with type II congenital methemoglobinemia due to the presence of neurological findings was presented. The patient's treatment was adjusted, the methemoglobin level was reduced, and cyanosis regressed, but no change was observed in neurological findings. This untreatable, rare condition must be included in the differential diagnosis of patients with unexplained cyanosis and high methemoglobin levels, and genetic counseling must be provided to the family, because of its severity and 25% recurrence rate. |
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