The patient presents with renal cysts and a family history of hypertension and renal calculi. Which protein is likely mutated?

• A. Fibrocystin
• B. Polycystin
• C. Nephrocystin
• D. Sodium-potassium-2 chloride cotransporter

Answer: (B)

In this scenario, the presence of renal cysts along with a family history of hypertension and renal calculi suggests a genetic condition related to cystic kidney diseases. The protein most likely mutated in this context is polycystin.

Polycystin is associated with autosomal dominant polycystic kidney disease (ADPKD), which is characterized by the formation of numerous cysts in the kidneys, leading to renal dysfunction, hypertension, and the potential for renal calculi due to urinary changes. The gene mutations affecting polycystin can cause abnormal cell signaling and disruption of normal kidney structure and function.

As for the other proteins listed, fibrocystin is typically associated with fibrocystic kidney disease, nephrocystin is linked to nephronophthisis, and the sodium-potassium-2 chloride cotransporter is involved in electrolyte balance but does not directly relate to cyst formation. Thus, polcystin stands out clearly as the likely mutated protein in the case of renal cysts and the defined family history.