Overview
Definition
A defect in distal tubule hydrogen ion secretion, leading to hyperchloremic metabolic acidosis with an inability to acidify urine below pH 5.5.
Epidemiology
Rare. Associated with autoimmune disorders (Sjögren's syndrome, SLE) and hereditary mutations.
Etiology & Risk Factors
- Inability of intercalated cells of distal tubule to secrete H+ into the lumen
- Associated with amphotericin B therapy, Sjögren's, and hypercalciuria
Clinical Symptoms
- Muscle weakness (due to hypokalemia)
- Nephrolithiasis / Nephrocalcinosis (calcium phosphate stones)
- Rickets or osteomalacia in children
Clinical Approach
Diagnosis
- Hyperchloremic metabolic acidosis with normal anion gap
- Inappropriately high urine pH (> 5.5) despite systemic acidosis
- Hypokalemia
- Positive urinary anion gap
Management
- Oral bicarbonate or citrate supplementation
- Potassium supplementation
Complications
- Kidney stones
- Nephrocalcinosis / CKD
- Growth retardation