What is the diagnosis for a patient with hypernatremia, hypokalemia, hyperchloremia, normal eGFR, hypocalcemia, hypomagnesemia, and hypophosphatemia?

Diagnosis: Gitelman Syndrome or Bartter Syndrome

The constellation of hypernatremia, hypokalemia, hyperchloremia, normal eGFR, hypocalcemia, hypomagnesemia, and hypophosphatemia is most consistent with Bartter syndrome, particularly given the preserved renal function and the characteristic pattern of renal electrolyte wasting with multiple concurrent deficiencies.

Primary Diagnostic Considerations

Bartter Syndrome as Leading Diagnosis

• Bartter syndrome classically presents with hypokalemia, metabolic alkalosis (though hyperchloremia can occur), hypomagnesemia, and hypocalcemia with preserved renal function 1
• The normal eGFR is a key distinguishing feature, as these tubular disorders do not initially impair glomerular filtration 1
• Hypomagnesemia occurs frequently in Bartter syndrome and requires specific attention, as magnesium deficiency impairs potassium repletion 2
• The simultaneous presence of hypophosphatemia, hypocalcemia, and hypomagnesemia creates a characteristic pattern where hypomagnesemia is associated with hypokalemia in 42% of cases and hypocalcemia in 22% of cases 3

Key Pathophysiologic Features

• Patients with Bartter syndrome exhibit inappropriate renal wasting of potassium, calcium, and magnesium despite low serum levels 4
• The hyperchloremia with hypokalemia suggests a non-anion gap metabolic disturbance with renal tubular dysfunction 1
• Hypomagnesemia must be corrected simultaneously with hypokalemia, as magnesium deficiency prevents effective potassium repletion 2, 4

Differential Diagnostic Algorithm

Rule Out Secondary Causes First

1. Medication-induced losses: Loop or thiazide diuretics cause substantial urinary potassium and magnesium wasting 2, 5
2. Gastrointestinal losses: Diarrhea can produce similar electrolyte patterns but typically with volume depletion 5
3. Post-obstructive diuresis: Following urinary tract obstruction relief, multiple electrolyte losses occur including hypokalemia, hypocalcemia, and hypomagnesemia 6

Confirm Primary Tubular Disorder

• Measure urinary electrolytes: Inappropriate magnesiuria, kaliuresis, and calciuria despite low serum levels confirm renal wasting 4
• Genetic testing: A panel including genes for Bartter syndrome (SLC12A1, KCNJ1, CLCNKB, BSND, CASR) and Gitelman syndrome (SLC12A3) should be performed 1
• Check for metabolic alkalosis rather than hyperchloremia, as the acid-base status helps differentiate subtypes 4

Critical Management Pitfalls

Avoid These Common Errors

• Do NOT attempt complete normalization of plasma potassium levels in Bartter syndrome, as this is often unachievable and may lead to overcorrection 1
• Do NOT use potassium citrate or other potassium salts that worsen alkalosis; only potassium chloride should be used 1
• Do NOT supplement salt in patients with secondary nephrogenic diabetes insipidus, as this worsens polyuria and risks hypernatremic dehydration 1
• Do NOT overlook magnesium replacement, as hypomagnesemia prevents correction of hypokalemia and hypocalcemia 2, 3

Specific Treatment Approach

Electrolyte Replacement Strategy

• Sodium chloride supplementation: 5-10 mmol/kg/day in divided doses throughout the day 1
• Potassium chloride supplementation: Use only potassium chloride, not citrate or other salts 1
• Magnesium supplementation: Organic magnesium salts have better bioavailability; maintain serum magnesium ≥0.70 mmol/L (1.7 mg/dL) 1, 7
• Spread supplements throughout the day to maintain stable levels 1

Pharmacologic Therapy

• NSAIDs (indomethacin or ibuprofen) should be considered in symptomatic patients, especially in early childhood 1
• Gastric acid inhibitors must be used together with nonselective cyclooxygenase inhibitors to prevent gastrointestinal complications 1
• Potassium-sparing diuretics, ACE inhibitors, or angiotensin receptor blockers are NOT routinely recommended 1

Monitoring Requirements

• Serial monitoring of plasma electrolytes is essential, as hypophosphatemia and hypomagnesemia often become apparent only after initial metabolic derangements are corrected 1
• Regular assessment every 6-12 hours in acute settings 8
• Frequency should be individualized based on severity and response to treatment 2