Liddle’s syndrome was first described by Dr Grant Liddle, an American endocrinologist, in 1963. It is an extremely rare genetic disorder. If one parent has the condition, his or her children will have a 50/50 chance of inheriting the defective gene or of being clear of the disorder.
Liddle’s syndrome is caused by over-activity of the principal cell within the kidney’s cortical collecting tubule. This results in too much sodium being reabsorbed into the bloodstream and an excessive loss of potassium in the urine.
Cases have also been documented of individuals with no family background of Liddle’s syndrome developing the disorder due to new mutations in the gene that causes it.
An early onset of hypertension (high blood pressure) is the principle – sometimes the only – symptom of Liddle’s syndrome. This can occur in late childhood or early adulthood.
Suspicion that the hypertension is secondary to an underlying condition will have been aroused by both its early onset and difficulty in controlling it, since conventional anti-hypertensive therapies are not effective in treating the high blood pressure caused by Liddle’s syndrome.
Other symptoms that may be present are abnormal heart rate, constipation and low blood potassium levels.
Patients with the symptoms above will be referred by their GPs to a hospital hypertension clinic for further evaluation. The tests that will be undertaken to establish a firm diagnosis will be blood tests – checking, among other things, for hormones associated with blood pressure and kidney function, and two types of 24-hour urine tests – the first to check for over-production of adrenaline and the second to measure the level of salt secretion.
Following diagnosis, patients are prescribed tablets to lower their blood pressure and correct their low potassium levels and resultant metabolic alkalosis.
Potassium supplements will not normally be needed in addition to therapy with one or other of these drugs. They also block the over-activity in the cortical collecting tubule, described above, which is the cause of Liddle’s syndrome.
Patients will need to remain on this treatment for life and will be offered follow up, either in an out patient clinic or by their GP. They will also be advised to maintain a low-sodium diet.
Left untreated, the symptoms of Liddle’s syndrome – in particular, the hypertension – could expose patients to the risk of a stroke, heart disease or kidney problems. However, while there is no surgical cure for Liddle’s syndrome, conservative treatment with drugs, in addition to dietary vigilance, will result in a good outlook for patients.