Bartter and Gitelman Syndromes
On this page
Direct answer
Bartter and Gitelman syndromes are inherited salt-losing tubulopathies that cause hypokalaemic metabolic alkalosis with normal or low blood pressure. Bartter syndrome arises in the thick ascending limb of Henle, whereas Gitelman syndrome lies in the distal convoluted tubule, and urinary calcium is the simplest bedside discriminator, being high in Bartter and low in Gitelman.
What you must remember
- Core picture: hypokalaemic metabolic alkalosis with salt wasting, high renin and high aldosterone, yet blood pressure is normal or low.
- Bartter site: the thick ascending limb, with NKCC2 defects in type 1 and ROMK defects in type 2 presenting antenatally with polyhydramnios and prematurity.
- Gitelman site: the distal convoluted tubule, due to loss of the thiazide-sensitive NCC cotransporter (SLC12A3), usually presenting in school age or adolescence.
- Calcium clue: Bartter shows hypercalciuria and sometimes nephrocalcinosis, whereas Gitelman shows hypocalciuria.
- Magnesium rule: Gitelman syndrome causes hypomagnesaemia, and magnesium must be replaced because low magnesium keeps renal potassium wasting going.
- Diuretic mimicry: covert loop diuretic use mimics Bartter and thiazide use mimics Gitelman, so a urine diuretic screen comes first.
- Treatment: potassium and sodium chloride supplements and potassium-sparing agents; indomethacin is used in some antenatal Bartter cases to block prostaglandin-driven salt wasting.
Comparing the two tubulopathies at a glance
A nine-year-old presents with cramps, tingling and a low potassium found on routine testing, with normal blood pressure. Another infant, born after polyhydramnios, has failure to thrive and nephrocalcinosis on ultrasound, and both conditions look alike on the blood gas.
| Feature | Bartter syndrome | Gitelman syndrome |
|---|---|---|
| Defect site | Thick ascending limb | Distal convoluted tubule |
| Main transporter or gene | NKCC2, ROMK, ClC-Kb, barttin | NCC (SLC12A3) |
| Typical onset | Antenatal to infancy | School age to adulthood |
| Urinary calcium | High, with nephrocalcinosis | Low |
| Serum magnesium | Normal or low | Usually low |
Urinary calcium and serum magnesium together separate the two groups in most children. Renin and aldosterone are high in both, so hormonal values alone do not distinguish them.
Blood gas values overlap considerably, so the site, age and calcium features carry most of the diagnostic weight. Sweat chloride is normal in both, which helps exclude cystic fibrosis, a mimic with hypochloraemic alkalosis. A spot urine calcium-to-creatinine ratio is a practical test for the calcium clue.
Where the exam sets its traps
Most errors come from labels applied before the urine and the drug history are examined.
- Trap: calling every salt-wasting child with normal blood pressure Bartter syndrome. Correct: Gitelman syndrome is the commoner picture in older children, and low urinary calcium with low magnesium points to it.
- Trap: diagnosing a genetic tubulopathy without asking about drugs. Correct: covert diuretic abuse produces the same biochemistry, so a urine diuretic screen comes before a genetic label.
- Trap: correcting potassium without replacing magnesium. Correct: low magnesium drives renal potassium wasting, so hypokalaemia stays refractory until magnesium is restored.
Frequently asked questions
How does urinary calcium differ in Bartter and Gitelman syndromes?
Bartter syndrome typically shows hypercalciuria, often with nephrocalcinosis, whereas Gitelman syndrome shows hypocalciuria. This single biochemical difference is the most useful bedside discriminator between the two.
Why does Gitelman syndrome usually present late?
Gitelman syndrome involves the thiazide-sensitive NCC transporter in the distal convoluted tubule, and its defect is generally milder than that of Bartter syndrome. Symptoms such as cramps, tetany and weakness therefore usually appear in school age or adolescence.
Why must magnesium be replaced in Gitelman syndrome?
Hypomagnesaemia increases renal potassium wasting, so hypokalaemia persists despite potassium supplements. Replacing magnesium is therefore a prerequisite for correcting potassium in Gitelman syndrome. Serum magnesium is therefore checked in every child with unexplained hypokalaemia.
Which drug history can mimic Bartter or Gitelman syndrome?
Covert loop diuretic use, such as furosemide, mimics Bartter syndrome, while thiazide use mimics Gitelman syndrome. A urine diuretic screen is therefore essential before a genetic diagnosis is accepted.