Genotype/phenotype observations in African Americans with Bartter syndrome.
BACKGROUND
Two Bartter syndrome phenotypes have been described, and molecular analyses demonstrate mutations in 1 of 3 genes encoding ascending limb of Henle transporters. We report phenotypic observations in 5 African American children with Bartter syndrome in the context of a distinct genotype.


METHODS
Mutation analyses were performed in 5 unrelated African American children with Bartter syndrome. These results were correlated to clinical and laboratory data. Calcium metabolism was evaluated with a bone disk bioassay.


RESULTS
Mutation analyses demonstrated homozygous deletion of the ClC-Kb gene in all children. Two children had polyhydramnios and premature birth; the others were born at term and presented with failure to thrive or dehydration. All receive indomethacin, spironolactone, and potassium chloride with improved but borderline hypokalemia. Growth has improved with therapy, but height SD scores range from -3.9- to -1.4. Urinary calcium excretion is normal, and bone disk bioassay shows no abnormal calciotropic activity. No patient had nephrocalcinosis, but renal sonograms show loss of corticomedullary differentiation.


CONCLUSIONS
African Americans with Bartter syndrome genotyped to date have homozygous deletion of ClC-Kb Clinical observations in our patients include partial correction of hypokalemia and suboptimal growth despite therapy. Abnormal calciotropic activity and nephrocalcinosis are not seen, but renal ultrasounds are abnormal.
Schurman
S J
SJ
Department of Pediatrics, Divisions of Nephrology and Genetics, University of South Florida College of Medicine and All Children's Hospital, St Petersburg, Florida, USA.
Perlman
S A
SA
Sutphen
R
R
Campos
A
A
Garin
E H
EH
Cruz
D N
DN
Shoemaker
L R
LR
D027321:Anion Transport Proteins; D001477:Bartter Syndrome / Q000188:drug therapy / Q000235:genetics*; D044383:Black People; D002118:Calcium / Q000378:metabolism; D018118:Chloride Channels / Q000235:genetics*; D004252:DNA Mutational Analysis; D017353:Gene Deletion; D005838:Genotype; D006801:Humans; D007213:Indomethacin / Q000627:therapeutic use; D007223:Infant; D007231:Infant, Newborn; D008565:Membrane Proteins; D010641:Phenotype; D011189:Potassium Chloride / Q000627:therapeutic use; D013148:Spironolactone / Q000627:therapeutic use; D001741:Black or African American
D027321:Anion Transport Proteins; C412733:CLCNKB protein, human; D018118:Chloride Channels; D008565:Membrane Proteins; D013148:Spironolactone; D011189:Potassium Chloride; D002118:Calcium; D007213:Indomethacin