**Question:** In type II Renal Tubular Acidosis (RTA), serum potassium level is -

A. Low
B. Normal
C. High
D. High

**Correct Answer:** A. Low

**Core Concept:**
Renal Tubular Acidosis (RTA) is a group of disorders that affect the ability of the kidneys to maintain the acid-base balance of the body. There are two main types of RTA: Type I and Type II. Type II RTA is characterized by impaired acidification of the urine, leading to a decrease in hydrogen ion concentration in the blood (hypocapnia) and increased serum potassium levels.

**Why the Correct Answer is Right:**
In Type II RTA, the impaired acidification of urine results in a compensatory mechanism to counteract the decreased acidity of blood. This mechanism involves the release of hydrogen ions (H+) from the cells into the bloodstream to lower the blood pH. As a result, the serum potassium levels increase since potassium ions (K+) are released from cells in response to the increased H+ ions in the blood.

**Why Each Wrong Option is Incorrect:**
Type II RTA is characterized by high serum potassium levels, not low. Therefore, options B (Normal) and D (High) are incorrect. Option C (High) is also incorrect because it contradicts the increased potassium levels due to the compensatory mechanism described above.

**Clinical Pearl:**
Type II RTA should be considered in patients presenting with symptoms like fatigue, weakness, and muscle cramps, as high serum potassium levels can lead to arrhythmias and cardiac arrest if left untreated. Monitoring of serum potassium levels and prompt diagnosis and treatment are essential to prevent serious complications.