Glucose-6-Phosphate Dehydrogenase Deficiency Presenting With Concurrent Hemolysis and Methemoglobinemia in a Young Woman: A Case Report of a Rare Medical Condition.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common red-cell enzymopathy worldwide, yet symptomatic disease in women is uncommon because of its X-linked inheritance. The coexistence of G6PD deficiency with methemoglobinemia is exceedingly rare, with only isolated reports in the literature. This overlap poses a unique therapeutic dilemma because methylene blue, the standard treatment for methemoglobinemia, requires nicotinamide adenine dinucleotide phosphate generated via the G6PD pathway and is, therefore, contraindicated in people with G6PD deficiency. We describe the case of a young woman presenting with her first hemolytic crisis in whom previously undiagnosed G6PD deficiency was complicated by significant methemoglobinemia. Early recognition of this dual presentation allowed for prompt discontinuation of methylene blue, treatment of hemolysis and methemoglobinemia with transfusion and ascorbic acid, and subsequent recovery. This case illustrates the importance of recognizing G6PD deficiency in discordant oximetry-arterial blood gas scenarios and avoiding methylene blue, particularly when dietary nitrites are a potential precipitant.