Factor VIII Response to Vasopressin in Nephrogenic Diabetes Insipidus

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Title: Factor VIII Response to Vasopressin in Nephrogenic Diabetes Insipidus
Authors: Toraldo, Roberto; D'Avanzo, Michele; Fazzone, Antonio; Papa, Maria L.; Santinelli, Raffaele; Tolone, Carlo; Iafusco, Ferdinando
Publisher: Journal of Pediatrics
Date Published: September 01, 1991
Reference Number: 316
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This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)

Certain blood factors respond to arginine vasopressin (AVP) or to a synthetic analog of AVP called DDAVP. After one researcher injected two NDI patients with DDAVP, he noticed that in each of them two of the blood factors that normally respond to DDAVP, factor VIII coagulant activity (FVIIIC) and factor VIII-related antigen (FVIIIR:Ag), did not respond. The researcher then tested the mothers of both NDI patients because they carried the NDI-causing gene and passed it on to their sons. (Mothers who carry the NDI-causing gene often do not fully express NDI symptoms. This is because the mutated NDI-causing gene is located on the X chromosome, and the mothers have the mutated gene on one X chromosome and a normal gene pair on their other X chromosome.) Both mothers had half the normal response to DDAVP in the two blood factors.

This led the researcher to suggest that the response of these two blood factors to DDAVP might be one way to diagnose for NDI and NDI carriers. However, later researchers came up with conflicting results when they sought to verify the initial researcher's suggestion.

D'Avanzo, et al., studied the response of FVIIC and FVIIIC:Ag to DDAVP in two unrelated NDI patients aged 2 and 5 years, and in their carrier mothers. The first patient had no marked increase in either FVIIIC or FVIIIR:Ag. Patient 2 showed a normal increase in FVIIIC, but no increase in FVIIIR:Ag. In both mothers, there was a normal increase of FVIIIC and no increase in FVIIIR:Ag.

The authors assume that NDI can be produced by different genes or combinations of genes. They warn that the response of these two blood factors to DDAVP as a means to diagnose NDI in patients or to identify carriers is not always a reliable diagnostic test, and that it should be used with caution.