**Core Concept**
Crigler Najjar type II syndrome is a congenital disorder characterized by a mild deficiency of the enzyme uridine diphosphate glucuronosyltransferase (UGT1A1), which plays a crucial role in bilirubin conjugation. This enzyme deficiency leads to elevated levels of unconjugated bilirubin, causing jaundice and potential neurological complications.

**Why the Correct Answer is Right**
The correct answer is a consequence of the partial deficiency of UGT1A1 enzyme in Crigler Najjar type II syndrome. This partial deficiency results in a moderate increase in unconjugated bilirubin levels, which can cause jaundice but is generally less severe than in Crigler Najjar type I syndrome, where the enzyme activity is almost completely absent. The elevated bilirubin levels in Crigler Najjar type II syndrome can be managed with phototherapy, which helps to break down unconjugated bilirubin.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Crigler Najjar type II syndrome involves a partial deficiency of UGT1A1 enzyme, not a complete absence.
**Option B:** This option is incorrect because Crigler Najjar type II syndrome is characterized by a moderate increase in unconjugated bilirubin levels, not a complete absence of bilirubin conjugation.
**Option D:** This option is incorrect because Crigler Najjar type II syndrome is a distinct clinical entity from Gilbert syndrome, which involves a partial deficiency of UGT1A1 enzyme but is generally milder and does not require treatment.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that Crigler Najjar type II syndrome is a treatable condition, and prompt recognition and management can prevent long-term neurological damage. Phototherapy is a key treatment modality for managing elevated bilirubin levels in this condition.

**Correct Answer: C.**