Which condition is most common inborn error of metabolism globally?

• A. Maple Syrup Urine Disease
• B. Phenylketonuria
• C. G6PD Deficiency
• D. Galactosemia

Answer: (C)

G6PD deficiency is the most widespread inborn error of metabolism worldwide because its deficiency is extremely common across diverse populations and is maintained at high carrier frequencies in malaria-endemic regions. G6PD is the first enzyme in the pentose phosphate pathway and is crucial for producing NADPH, which helps protect red blood cells from oxidative damage. When G6PD is deficient, red cells become vulnerable to oxidative stress from infections, certain drugs, fava beans, and other triggers, leading to hemolysis. The combination of a high global population frequency and the broad geographic distribution, especially in areas historically exposed to malaria where the mutation provides some protection against the parasite, drives its status as the most common metabolic-inborn defect observed worldwide.

In contrast, conditions like phenylketonuria, galactosemia, and maple syrup urine disease are comparatively rarer in most populations, which is why they are less likely to be the most common globally. However, they are still important metabolic disorders with distinct management implications, such as dietary restrictions and newborn screening.