**Core Concept:** Dent's disease is a rare primary tubulopathy characterized by proximal renal tubular dysfunction, leading to nephrocalcinosis and nephrolithiasis. It is caused by mutations in the CLCN5 or DENT1 gene, encoding proteins involved in chloride transport in the renal tubules.

**Why the Correct Answer is Right:** On laboratory evaluation, Dent's disease presents with elevated blood and urine phosphate levels, high urine calcium-to-creatinine ratio, and low urine phosphate excretion. This is due to the impaired reabsorption of phosphate in the renal tubules, leading to increased phosphate excretion in urine. Additionally, elevated blood and urine calcium levels are often seen, which is attributed to increased calcium reabsorption in the renal tubules.

**Why Each Wrong Option is Incorrect:**

A. Low blood phosphate levels - This is incorrect because Dent's disease results in elevated blood phosphate levels due to impaired reabsorption in the renal tubules.

B. Normal blood and urine calcium levels - Although blood calcium levels may be normal in some cases, the primary abnormality in Dent's disease is the elevated phosphate levels, not calcium.

C. Increased urine phosphate excretion - This is incorrect because, as mentioned earlier, Dent's disease results in impaired phosphate reabsorption in the renal tubules, leading to decreased urine phosphate excretion.

D. Low urine calcium excretion - Similar to urine phosphate excretion, the primary abnormality in Dent's disease is the elevated phosphate levels, not calcium. Elevated urine calcium may be present in some cases due to increased calcium reabsorption in the renal tubules.

**Clinical Pearl:** In Dent's disease, the key laboratory findings are elevated blood phosphate and urine phosphate levels, along with decreased urine phosphate excretion. While elevated blood and urine calcium levels may be observed, the primary abnormality is the elevated phosphate levels, which lead to nephrocalcinosis and nephrolithiasis.