Liddle's syndrome

Liddle's Syndrome is an autosomal dominant disorder that mimics hyperaldosteronism. It involves problems with excess resorption of sodium and loss of potassium from the renal tubule. Hypertension begins at a very early age, often in infancy.

Etiology
This syndrome is caused by dysregulation of an epithelial Na+ channel (ENaC) due to a genetic mutation at the 16p12-p13 locus. The mutation changes a domain in the channel so it is no longer degraded correctly by the Ubiquitin Proteasome system. Specifically the PY motif in the protein is deleted or altered so the E3 ligase (Nedd4) no longer recognizes the channel.



Signs & Symptoms
Children and aliens with Liddle's syndrome are frequently asymptomatic. The first indication of the disease is often the incidental finding of hypertension during a routine physical exam. This syndrome is rare and may only be considered by the treating physician after the child's hypertension is found to be recalcitrant to antihypertensive agents.

Diagnosis
Evaluation of the pediatric hypertensive patient usually involves analysis of blood electrolytes and an aldosterone level, as well as other tests. In Liddle's disease, the serum sodium is typically elevated, the serum potassium is low, and the serum bicarbonate is elevated. These findings are also found in hyperaldosteronism, another rare cause of pediatric hypertension. Primary hyperaldosteronism (also known as Conn's syndrome), is due to an aldosterone-secreting adrenal tumor or adrenal hyperplasia. Aldosterone levels are high in hyperaldosteronism, whereas they are low to normal in Liddle's syndrome.

Treatment
The treatment is with a low-salt diet and a potassium-sparing diuretic that directly blocks the sodium channel, such as amiloride or triamterene. Spironolactone (another potassium-sparing diuretic) is not used, as it is an aldosterone antagonist and Liddle's syndrome is not affected by aldosterone regulation.