Okay, let's tackle this question. The patient is a 5-year-old girl with hypertension, virilization, and hypokalemia. The key here is to link these symptoms to the underlying condition.

Hypertension and hypokalemia often point to conditions involving mineralocorticoid excess. Virilization suggests androgen excess. The combination makes me think of congenital adrenal hyperplasia (CAH), specifically 21-hydroxylase deficiency. This enzyme is crucial in cortisol and aldosterone synthesis. When it's deficient, there's a buildup of precursor steroids, leading to increased androgen production (causing virilization) and reduced aldosterone, which can cause salt-wasting or, in some cases, mineralocorticoid excess from the accumulation of 11-deoxycorticosterone (DOC). DOC has both mineralocorticoid and weak glucocorticoid activity. This leads to hypertension and hypokalemia due to sodium retention and potassium loss.

Now, looking at other options. Congenital adrenal hyperplasia due to 11β-hydroxylase deficiency is another possibility. This enzyme is needed for converting DOC to cortisol. Deficiency here would also lead to DOC accumulation, causing similar symptoms. However, 21-hydroxylase is more common. 17α-hydroxylase deficiency might cause hypertension but with hypogonadism, not virilization. Arrhythmogenic right ventricular cardiomyopathy is unrelated to the endocrine findings. So the most likely answer is 21-hydroxylase deficiency.

The clinical pearl here is that in a child with hypertension, hypokalemia, and virilization, 21-hydroxylase deficiency should be high on the differential. The key is the combination of mineralocorticoid excess and androgen excess leading to the classic triad.

**Core Concept**
The triad of hypertension, hypokalemia, and virilization in a child points to **congenital adrenal hyperplasia (CAH)** due to **21-hydroxylase deficiency**. This enzyme deficiency disrupts cortisol and aldosterone synthesis, leading to **mineralocorticoid excess** (via 11-deoxycorticosterone) and **androgen overproduction**.

**Why the Correct Answer is Right**
21-Hydroxylase deficiency causes a block in the cortisol and aldosterone synthesis pathways. Accumulated **11-deoxycorticosterone (DOC)** acts as a mineralocorticoid analog, causing **sodium retention (hypertension)** and **potassium loss (hypokalemia)**. Simultaneously, shunting of precursors into the androgen pathway results in **virilization**. Classic CAH (salt-wasting form) also presents with hypoglycemia, but the non-classic form may present later with isolated virilization or hypertension.

**Why Each Wrong Option is Incorrect**
**Option A:** 11β-Hydroxylase deficiency causes hypertension and virilization but presents with **hyponatremia** (due to mineralocorticoid deficiency) and **hyperkalemia** (due to aldosterone deficiency), conflicting with hypokalemia here.
**Option B:** 17α-Hydroxylase deficiency

✓ Correct Answer: C. 11-ss hydroxylase deficiency