NBME Decreased activity in the enzyme that reduces Fe3+ to Fe2+ (NBME Answers)

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free120/Block 2/Question#39 (8.5 difficulty score)
A 3-month-old boy is brought to the emergency ...
Decreased activity in the enzyme that reduces Fe3+ to Fe2+🔍,📺
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+7
submitted by aejinkim(7),

the hypoxia and the "blood sample appears brown" should point you towards methemoglobinemia.

if you want a fun video from "9-1-1" that actually explains a lot of it: https://www.youtube.com/watch?v=LFmlRzQ-0RA

xmen very nice videos +++ +1

+1
submitted by madden875(19),

From wikipedia:

"Spontaneously formed methemoglobin is normally reduced (regenerating normal hemoglobin) by protective enzyme systems, e.g., NADH methemoglobin reductase (cytochrome-b5 reductase), NADPH methemoglobin reductase, and the ascorbic acid and glutathione enzyme systems. Disruptions with these enzyme systems lead to methemoglobinemia."

+0
submitted by mariame(8),

https://www.medicalnewstoday.com/articles/321955#:~:text=The%20most%20common%20cause%20of,is%20unable%20to%20carry%20oxygen.

I was wondering why a baby could get methemoglobinemia. Some answers in the link.

+0
submitted by hemoglobin_(1),

The congenital type is due to a deficiency of the enzyme NADH-cytochrome b5 reductase, which impairs the ability of hemoglobin to bind oxygen, leading to poor oxygenation of body tissues. Cyanosis and hypoxia result. Source: https://www.visualdx.com/visualdx/diagnosis/methemoglobinemia?moduleId=101&diagnosisId=56035