A–13–year old boy is referred for evaluation of nocturnal enuresis and short stature. His blood pressure is normal. The hemoglobin level is 8g/dl.urea 112 mg/dl, creatinine 6 mg/dl, sodium 119 mEq/ dl, potassium 4 mEq/l, calcium 7 mg/dl, phosphate 6 mg/dl and alkaline phosphatase 300 U/I. Urinalysis shows trace proteinuria with hyaline casts; no red and white cells are seen. Ultrasound shows bilateral small kidneys and the micturating cystourethrogram is normal. The most likely diagnosis is –

**Core Concept**
The patient presents with a complex clinical picture of nocturnal enuresis, short stature, and renal dysfunction, making it essential to consider a diagnosis that encompasses multiple systems, including the kidneys, electrolytes, and endocrine system.

**Why the Correct Answer is Right**
The patient's laboratory results reveal a low hemoglobin level, elevated urea and creatinine levels, indicating impaired renal function, and a low calcium level. Additionally, the presence of small kidneys on ultrasound and trace proteinuria with hyaline casts in the urinalysis further support renal involvement. The normal micturating cystourethrogram rules out obstructive uropathy, and the patient's normal blood pressure suggests that the renal impairment is not due to chronic hypertension. The combination of these findings, particularly the low calcium level and renal dysfunction, suggests a diagnosis of Fanconi syndrome, which is often seen in patients with renal tubular acidosis (RTA). However, the presence of hypocalcemia and the laboratory findings point towards a more specific diagnosis of Fanconi syndrome due to **Cystinuria**. Cystinuria is a genetic disorder characterized by the defect in the transport of cystine and dibasic amino acids in the kidneys, leading to their excessive excretion in the urine.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided, as the correct answer is not provided.

**Clinical Pearl / High-Yield Fact**
Cystinuria is an autosomal recessive disorder that affects the transport of cystine and dibasic amino acids in the kidneys, leading to their excessive excretion in the urine. Patients with cystinuria are at risk of developing kidney stones composed of cystine, which can cause obstructive uropathy and renal failure.

**Correct Answer:** C.

✓ Correct Answer: D. Nephronophthisis