**Question:** Which one of the following statements is wrong regarding adult polycystic kidney disease -

A. Adult polycystic kidney disease (APKD) is a genetic disorder caused by mutations in PKD1 or PKD2 genes.
B. Patients with APKD typically develop multiple cysts in both kidneys.
C. The cysts in APKD are lined by simple cuboidal epithelial cells.
D. APKD is a rare disease affecting less than 1% of the population.

**Correct Answer:**

D. Adult polycystic kidney disease (APKD) is a rare disease affecting less than 1% of the population.

**Core Concept:**

Adult polycystic kidney disease (APKD) is a genetic disorder characterized by the abnormal formation of fluid-filled cysts in the kidneys. These cysts can lead to progressive kidney enlargement, impaired kidney function, and hypertension. APKD is caused by mutations in PKD1 or PKD2 genes, which encode polycystin-1 and polycystin-2 proteins that are essential for maintaining kidney tubule structure and function.

**Why the Correct Answer is Right:**

APKD is not a rare disease affecting less than 1% of the population. Instead, it is a relatively common hereditary disorder, affecting approximately 1 in 1,000-2,000 individuals worldwide. Mutation of PKD1 or PKD2 genes is the primary cause of APKD, leading to the production of abnormal polycystin-1 and polycystin-2 proteins. These proteins are crucial for maintaining the structure and function of kidney tubules, which are essential for reabsorbing essential substances and excreting waste products.

**Why Each Wrong Option is Incorrect:**

A. While PKD1 and PKD2 mutations contribute to APKD, the exact cause of the disease is not fully understood. The statement "less than 1% of the population" is incorrect as APKD affects a larger proportion of the population.

B. The formation of multiple cysts in both kidneys is a key feature of APKD, which contrasts with the statement that APKD is a rare disease.

C. Cysts in APKD are lined by simple cuboidal epithelial cells, not "simple cuboidal epithelial cells." Simple cuboidal cells are typically found in normal kidney tubules, while cysts in APKD have a more complex structure involving multiple layers of epithelial cells.

D. The statement "less than 1% of the population" is incorrect, as APKD affects a larger proportion of the population as mentioned earlier.

**Clinical Pearls:**

Understanding the genetic basis and clinical features of APKD is crucial for healthcare professionals as it can lead to early diagnosis, prognosis, and appropriate management of kidney disease. Genetic testing and regular monitoring of kidney function are essential for affected individuals to prevent complications, such as hypertension, renal failure, and the need for kidney transplantation.