Anemia e desaturazione... uno strano caso di favismo

Methemoglobinemia is a rare but significant complication in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. In these individuals, oxidative stress - triggered by infections, drugs, or foods like fava beans - can convert hemoglobin iron from its ferrous (Fe2+) to ferric (Fe3+) state, forming methemoglobin (MetHb), which is unable to bind and transport oxygen. Normally, MetHb is reduced back via NADPH-dependent pathways, but in G6PD-deficient patients, NADPH production is impaired, leading to accumulation of MetHb and resulting in tissue hypoxia unresponsive to oxygen therapy. Clinical suspicion should arise in patients with acute hemolysis, normal lung findings, and persistent low SpO2 despite oxygen supplementation. Diagnosis is confirmed by blood gas analysis. Treatment is supportive, as methylene blue is contraindicated due to its oxidant properties. Recognizing this mechanism is essential for safe and effective management.