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A boy of Mediterranean descent develops dark urine and jaundice 2 days after eating fava beans. He had a similar episode after taking sulfamethoxazole.
XLR; G6PD
- Common variants: A- (African), Mediterranean, Asian
- Most common enzyme deficiency worldwide
- Episodic hemolysis triggered by oxidative stress
- Triggers: Fava beans, sulfonamides, antimalarials, infections
- Bite cells, Heinz bodies on smear (during crisis)
- Neonatal jaundice
- Quantitative G6PD enzyme activity assay (spectrophotometric): the standard diagnostic test
- Test when not in acute crisis: young reticulocytes have higher enzyme activity and can mask deficiency, giving false-normal results during hemolysis
- Confirmatory G6PD molecular testing identifies the specific variant (A-, Mediterranean, etc.)
- Carrier detection in heterozygous females can be unreliable by enzyme assay due to X-inactivation; molecular testing is preferred
- Avoid triggers, supportive care during crises