Okay, let's tackle this question about the 'boiled cabbage' smell of urine. First, I need to remember which metabolic disorders are associated with specific urine odors. The question is asking about the cause of this particular smell.

I recall that maple syrup urine disease is known for a sweet, maple-like odor, but that's not the case here. Then there's phenylketonuria, which can have a musty odor. Wait, maybe it's isovaleric aciduria? I think that's the one with the sweaty sock or cabbage smell. Oh right, isovaleric aciduria is also called "sweatfoot syndrome" because of the odor. The smell can be described as similar to boiled cabbage.

So the core concept here is organic acidemias and their characteristic odors. The correct answer should be isovaleric aciduria. Let me check why the other options are wrong. Maple syrup urine disease is a branched-chain ketoacidosis, so that's out. Propionic acidemia has a pungent, cheesy smell. Glutaric aciduria type I might have a different odor. Methionine malabsorption, like in cystathioninuria, doesn't typically present with a urine odor.

Wait, another possibility is trimethylaminuria, which has a fishy odor. No, that's not it. So the key is to link the cabbage smell to isovaleric aciduria. The clinical pearl here is remembering the specific odors associated with each inborn error. For exams, these are high-yield facts. The correct answer is option C, assuming the options are listed correctly. Let me structure the explanation now.

**Core Concept**
The "boiled cabbage" odor in urine is a hallmark of **isovaleric aciduria**, an inborn error of metabolism affecting leucine catabolism. This autosomal recessive disorder results from deficiency of **isovaleryl-CoA dehydrogenase**, leading to accumulation of isovaleric acid, which imparts the characteristic smell.

**Why the Correct Answer is Right**
In isovaleric aciduria, impaired breakdown of leucine causes accumulation of isovaleric acid, a volatile compound with a pungent, cabbage-like odor. The acid is excreted in urine, producing the diagnostic feature. Acute episodes may cause metabolic acidosis, encephalopathy, and ketosis, often triggered by infections or fasting. Early diagnosis via newborn screening and dietary management are critical.

**Why Each Wrong Option is Incorrect**
**Option A:** Maple syrup urine disease (MSUD) causes a sweet, syrupy odor due to branched-chain ketoacid accumulation.
**Option B:** Propionic acidemia presents with a pungent, cheesy or "sweaty" odor, not cabbage-like.
**Option D:** Glutaric aciduria type I may cause hypoglycemia and macrocephalus but lacks the specific cabbage smell.

**Clinical Pearl / High-Yield Fact**
Remember the "cabbage" smell as a key clue for isovaleric aciduria. On exams, linking specific urine odors (e.g., maple syrup = MSUD, fishy = trimethylaminuria) to metabolic disorders can quickly narrow differential diagnoses. Always consider inborn errors in neonates with metabolic acidosis and characteristic odors.

**Correct Answer: C.

✓ Correct Answer: C. Hypermethioninemia