**Core Concept**
Adrenal insufficiency, particularly congenital adrenal hyperplasia (CAH), is a critical condition that can lead to life-threatening consequences if not promptly diagnosed and treated. It involves a deficiency in cortisol production, resulting in an accumulation of precursor hormones, such as 11-deoxycortisol, which can be converted to androgens, causing virilization and increased pigmentation.

**Why the Correct Answer is Right**
The infant's presentation of increased pigmentation, normal genitalia appearance, and hypoglycemia (blood glucose level of 30 mg/dL) is suggestive of CAH due to 21-hydroxylase deficiency, the most common cause of CAH. This enzyme deficiency leads to an accumulation of 11-deoxycortisol, which can be converted to androgens, causing virilization and increased pigmentation. Additionally, the deficiency of cortisol leads to an inability to glucocorticoid-mediated gluconeogenesis, resulting in hypoglycemia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the infant's increased pigmentation and virilization, which are characteristic features of CAH.
**Option B:** This option is incorrect because it does not explain the infant's hypoglycemia, which is a direct result of cortisol deficiency.
**Option C:** This option is incorrect because it does not account for the infant's normal genitalia appearance, which is typically affected in CAH due to androgen excess.

**Clinical Pearl / High-Yield Fact**
CAH due to 21-hydroxylase deficiency is the most common cause of CAH, accounting for approximately 90-95% of cases. It is an autosomal recessive disorder, and affected infants often present with hypoglycemia, virilization, and increased pigmentation.

**Correct Answer:** D (Note: Correct answer letter is missing. Assuming it's option D for this explanation.)