Utility of AVP gene testing in familial neurohypophyseal diabetes insipidus.
BACKGROUND
Familial neurohypophyseal diabetes insipidus (FNDI) is a rare disorder resulting from arginine vasopressin (AVP) gene mutations. A partial defect in AVP secretion occurs early in the course of FNDI and may not be detected by a water deprivation test (WDT). Testing for AVP gene mutations may confirm a diagnosis of FNDI when a WDT is inconclusive and may also predict individuals who will later develop FNDI.


OBJECTIVE
To test the utility of AVP gene analysis in confirming the diagnosis of FNDI.


METHODS
Five families (20 subjects, 14 symptomatic and six asymptomatic) with FNDI and nine children with idiopathic neurohypophyseal diabetes insipidus (INDI).


METHODS
Genomic DNA was analysed for AVP gene mutations using polymerase chain reaction (PCR) amplification and sequencing.


RESULTS
Heterozygous AVP gene mutations were found in all subjects with FNDI but none of the ICDI patients. Each family had their own distinct mutation. We identified two novel mutations (C44W and C105S). One asymptomatic subject developed diabetes insipidus (DI) 4 months after detection of an AVP gene mutation. The WDT suggested partial DI in 4/6 but was normal in 2/6 children with FNDI.


CONCLUSIONS
AVP gene testing allowed diagnostic confirmation of FNDI when the WDT was inconclusive in symptomatic children, therefore obviating the need for a repeat WDT and enabling earlier initiation of appropriate treatment. AVP gene testing also has the potential to identify which asymptomatic children will later develop FNDI.
Chitturi
Sridhar
S
Paediatric Endocrinology and Diabetes, Mater Children's Hospital, Brisbane, Australia.
Harris
Mark
M
Thomsett
Michael J
MJ
Bowling
Francis
F
McGown
Ivan
I
Cowley
David
D
Leong
Gary M
GM
Batch
Jennifer
J
Cotterill
Andrew M
AM
D001127:Arginine Vasopressin / Q000235:genetics* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D020790:Diabetes Insipidus, Neurogenic / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D010904:Pituitary Gland, Posterior / Q000002:abnormalities; D014868:Water Deprivation
D001127:Arginine Vasopressin