**Question:** Triad of Fetty's syndrome does not include:

A. Pulmonary hypertension
B. Congenital heart disease
C. Chronic renal failure
D. Hyperkalemia

**Core Concept:** Fetty's syndrome is a clinical entity characterized by three cardinal signs: hyperkalemia, hyperkalemic periodic paralysis, and pulmonary hypertension. It is a rare condition associated with mutations in the SCN4A gene, which encodes the voltage-gated sodium channel (Nav1.4) found in skeletal muscles and cardiac muscles.

**Why the Correct Answer is Right:** The correct answer, D. Hyperkalemia, is not part of the triad because hyperkalemia is a consequence of the syndrome, not a cause or component of the clinical presentation. The triad consists of hyperkalemic periodic paralysis, pulmonary hypertension, and hyperkalemia.

**Why Each Wrong Option is Incorrect:**

A. Pulmonary hypertension is a component of the triad, as it is a consequence of the underlying genetic defect causing abnormal sodium channels.
B. Congenital heart disease is not part of the triad, as it is not directly related to the genetic defect in SCN4A gene or the resulting hyperkalemic periodic paralysis.
C. Chronic renal failure is not part of the triad because it is not directly associated with the specific genetic defect or the resulting hyperkalemic periodic paralysis.

**Clinical Pearl:** The triad of Fetty's syndrome highlights the importance of considering genetic disorders in the differential diagnosis of patients presenting with hyperkalemic periodic paralysis and pulmonary hypertension. Early recognition and genetic testing can lead to appropriate management and counseling for affected individuals and their families.