Craig HD, Hansson JH, Feld L, Yadin O, Farquet C, Bowlin D,
Shackleton C, Lifton RP
Prospective molecular genetic diagnosis of apparent
mineralocorticoid excess and Liddle's syndrome
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1548 1996
Apparent mineralocorticoid excess (AME) and Liddle's syndrome (LS)
are easily confused forms of severe hypertension with hypokalemic
alkalosis. In both cases, there is increased sodium reabsorption via the
apical epithelial sodium channel. AME is caused by mutations in
11-beta-hydroxysteroid dehydrogenase (11-beta-HSD), while LS is
cased by mutation in the apical sodium channel. There is a high
cortisol:cortisone ratio in AME, and autosomal dominant transmission in
LS.
Because the diagnosis is so difficult, the authors investigated 4
cases previously published as having LS. They found that there were
no mutations in the sodium channel subunits, calling the diagnosis of LS
into question. They then considered a diagnosis of AME. While the
sodium channels were normal, the found mutations in 11-beta-HSD in all
4 patients. They diagnosis was confirmed by finding high urinary cortisol
to cortisone ratio. A 5th patient with severe hypertension and
hypokalemic alkalosis, but no family history of hypertension, was found
to have de novo LS.
Comment: This study demonstrates the utility of molecular tools
to aid in the diagnostic differentiation between LS and AMD, two clinical
diagnoses that are different to separate on clinical grounds. We will be
seeing more of this type of molecular diagnosis in the future
(see
Abstract A1810).
(Robert A. Star, M.D., University of Texas Southwestern Medical
School, Dallas)
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Am Soc Nephrol
H: Pathophysiology :
Hormonal aberrations
Acidosis/alkalosis :
Hypokalemia