Updated: 8/11/2017

Syndrome of Apparent Mineralocorticoid Excess (SAME)

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Snapshot
  • A 10-year-old boy with autism presents to his pediatrician’s office for muscle weakness. He has been refusing all food except licorice. His parents have been buying him bags of licorice in an effort to prevent starvation. Laboratory test reveals hypokalemia and metabolic alkalosis. His parents are counseled about eating excessive licorice and the family is referred to a specialist center for behavioral therapy.
Introduction
 

 
  • Clinical definition
    • Syndrome of Apparent Mineralocorticoid Excess (SAME) is a hereditary defect in 11β-hydroxysteroid dehydrogenase causing
      • hypertension
      • hypokalemia
      • metabolic alkalosis
    • these findings are similar to those in primary aldosteronism
  • Epidemiology
    • demographics
      • early childhood onset
    • risk factors
      • family history
  • Etiology
    • hereditary deficiency
    • acquired disorder
      • ingestion of glycyrrhetinic acid (licorice)
  • Pathogenesis
    • genetic loss-of-function mutation in 11β-hydroxysteroid dehydrogenase (kidney isoform)
      • 11β-hydroxysteroid dehydrogenase usually converts cortisOL to cortisONE
        • cortisOL can activate mineralocorticoid receptors (in fact, similar affinity with aldosterone)
        • cortisone is inactive
      • deficiency results in excess cortisol, which will increase activation of mineralocorticoid receptor
    • glycyrrhetinic acid inhibits 11β-hydroxysteroid dehydrogenase and reduces gene expression
  • Genetics
    • inheritance pattern
      • autosomal recessive
    • mutations
      • chromosome 16
      • 11β-HSD2 gene
  • Associated conditions
    • nephrogenic diabetes inspidus
      • induced by chronic hypokalemia
Presentation
  • Symptoms
    • infants
      • low birth weight
      • failure to thrive
  • Physical exam
    • muscle weakness due to hypokalemia
    • hypertension
Studies
  • Labs
    • hypokalemia
    • metabolic alkalosis
    • ↓ aldolsterone level
    • ↓ renin activity
    • may have ↑ creatinine
  • Urine
    • hypercalciuria
    • free cortisol to free cortisone ratio on 24-hour urine collection
      • normal ratio is 0.3-0.5
      • in hereditary disorder, ratio is 5-18
      • in licorice ingestion, ratio is only modestly elevated
Differential
  • Liddle syndrome
    • urine cortisol to cortisone ratio is normal
  • Primary aldosteronism
    • elevated aldosterone
Treatment
  • Conservative
    • remove licorice from diet
      • indications
        • for those with acquired SAME from licorice ingestion
  • Medical
    • mineralocorticoid blockade
      • indications
        • for those with hereditary SAME
      • drugs
        • spironolactone
        • eplerenone
        • amiloride
        • triamterene
    • corticosteroids
      • indications
        • if mineralocorticoid blockade is not effective or tolerated
    • thiazides
      • indications
        • hypercalciuria
Complications
  • Cardiac arrhythmia from hypokalemia

References

 

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