Gray baby syndrome is caused by :
**Core Concept**
Gray baby syndrome is a rare but life-threatening condition that occurs in newborns due to an accumulation of sulfhemoglobin, a compound that forms when sulfonamides, especially sulfadiazine, are metabolized in the presence of a deficiency of the enzyme diaphorase (also known as NADPH cytochrome P450 reductase). This condition is characterized by cyanosis, vomiting, and abdominal distension.
**Why the Correct Answer is Right**
The correct answer is related to the metabolism of sulfonamides. Sulfhemoglobin is formed when sulfonamides are metabolized by the enzyme diaphorase. In newborns, the activity of this enzyme is low, leading to an accumulation of sulfhemoglobin and the characteristic symptoms of gray baby syndrome. This condition is often associated with the use of sulfadiazine, a sulfonamide antibiotic.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not related to gray baby syndrome.
**Option B:** This option is not correct as it does not relate to the metabolism of sulfonamides.
**Option C:** This option is incorrect as it does not describe the underlying cause of gray baby syndrome.
**Clinical Pearl / High-Yield Fact**
Gray baby syndrome is a classic example of a drug-induced condition that highlights the importance of careful consideration of the pharmacokinetics and pharmacodynamics of medications in vulnerable populations, such as newborns.
**Correct Answer:** D. Sulfadiazine.