Successful Treatment of Methemoglobinemia in Two Boys with G6PD Deficiency and Favism Following Ascorbic Acid Therapy

Warittha Supho; Surapong Lertthammakiat; Priengrutai Prasopchoknapaporn

doi:10.69898/jhtm.36.2026.287752

Authors

Warittha Supho Ramadhibodi Chakri Naruebodindra Hospital, Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Samut Prakan, Thailand
Surapong Lertthammakiat Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Samut Prakan, Thailand
Priengrutai Prasopchoknapaporn Ramadhibodi Chakri Naruebodindra Hospital, Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Samut Prakan, Thailand

DOI:

https://doi.org/10.69898/jhtm.36.2026.287752

Keywords:

G6PD deficiency, methemoglobinemia, favism, ascorbic acid

Abstract

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common X-linked hematological disorder that predisposes individuals to acute hemolysis under oxidative stress. A rare complication is the co-occurrence of favism and methemoglobinemia, a condition where hemoglobin is oxidized to the ferric (Fe³⁺) state, impairing oxygen transport. Management is complicated because methylene blue, the first-line treatment for methemoglobinemia, is contraindicated in G6PD deficiency.

Case Report: This report describes two Thai boys (aged 2.8 and 3.2 years) who presented with respiratory distress, low oxygen saturation (SpO₂ 83–89%), unresponsive to oxygen therapy, and dark urine following fava bean ingestion. Laboratory findings revealed acute intravascular hemolysis with presence of ghost and blister cells on peripheral blood smears, alongside elevated methemoglobin levels (3.3% and 8.0%). Both patients were newly diagnosed with G6PD deficiency, with case 1 confirmed as the G6PD Mahidol mutation (487G>A) and case 2 confirmed as the G6PD Viangchan mutation (871G>A). Due to the contraindication of methylene blue, both patients were treated with ascorbic acid (intravenous in case 1; oral in case 2) and blood transfusions. The oxygen saturation normalized within 2 and 5 hours after ascorbic acid administration, respectively.

Conclusion: The co-occurrence of favism and methemoglobinemia is rarely reported, with only 16 previous cases. These cases highlight the importance of recognizing methemoglobinemia in G6PD-deficient patients presenting with desaturation and demonstrate that ascorbic acid is a safe, effective alternative for the treatment of methemoglobinemia. However, careful consideration of ascorbic acid dosage is essential to avoid potential pro-oxidant effects.

Keywords: G6PD deficiency, methemoglobinemia, favism, ascorbic acid

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