Calado J, Saunier S, Konrad M, Benessy F, Silbermann F, et al
Molecular diagnosis: a substitute for renal biopsy in
nephronophthisis
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1611 1996
Familial juvenile nephronophthisis (NPH) is an autosomal recessive
chronic tubulointerstitial nephritis that progresses to ESRD during
adolescence. The diagnosis is made by characteristic anatomical
alterations: the tubular basement membrane is thickened and split, and
there are medullary cysts. This disease can be suspected in affected
families using a maximal concentrating ability test and ultrasound. The
gene responsible for this disorder has been mapped to chromosome 2,
region 2q13. A large deletion (NPH1) is found in most families and
65% of spontaneous mutations.
The authors have developed a
PCR-based method to detect the deletion. The deletion was detected in 2
patients known to have NPH, and in 1 of 6 younger sibs. Of note, two sibs
with abnormal urine concentrating defects did not have the deletion,
suggesting that they did not have the disease, and that the concentration
defect was a false positive. In one sib, the abnormal deletion was
detected at 6 months of age; a concentration test turned positive 1 year
later. In conclusion, this PCR assay allows for easy and rapid molecular
diagnosis of this hereditary renal disease.
Comment: This is an exciting preliminary description of a
PCR-based test that should allow for presymptomatic and prenatal
diagnosis in affected families without resorting to a renal biopsy. The
diagnostic accuracy must be evaluated in a larger series. However, one
must remember that this test only identifies a single defect (NPH1), and
will not pick up other genetic defects in this area that may cause the NPH
syndrome. We will be seeing more of this type of molecular diagnosis in
the future (see
Abstract A1492).
(Robert A. Star, M.D., University of Texas Southwestern Medical
School, Dallas)
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Am Soc Nephrol
Proteinuria/Hematuria :
Hereditary hematuria/proteinuria
Cystic disease :
Hereditary polycystic disease