INHERITANCE OF VON-WILLEBRAND-FACTOR DEFICIENCY IN DOBERMAN-PINSCHERS

Objective - To determine the inheritance of von Willebrand factor (vWF ) deficiency in Doberman Pinschers. Design - Prospective, observationa l study. Animals - 26 adult Doberman Pinschers or mixed-breed dogs and 101 pups produced from 18 matings between adult dogs. Procedure - Mea surement of plasma VWF concentrations in parents and progeny. On the b asis of plasma VWF concentrations, dogs were grouped as normal (75 to 160 U of vWF/dl), midrange (greater than or equal to 30 and < 75 U of vWF/dl), or low (< 30 U of vWF/di). Results - The percentile distribut ion of VWF concentrations was trimodal. Distribution between dogs with low and midrange plasma vWF concentrations changed sharply, whereas t he change between dogs with midrange and normal plasma VWF concentrati ons was gradual. Three matings between dogs with low VWF concentration s produced 13 offspring, all with low VWF concentrations. Two matings between dogs with normal plasma vWF concentrations produced 14 offspri ng, all with normal vWF concentrations. Eight matings between dogs wit h normal and low plasma VWF concentrations produced 54 offspring, 40 w ith midrange, 13 with normal, and 1 with low vWF concentrations. There were 5 matings of dogs with midrange plasma VWF concentrations to dog s with low, midrange, or high VWF concentrations. The results of ail m atings were consistent with a single gene defect where each normal all ele produced half the total amount of VWF when both alleles are normal and each defective allele produced < 15 U of vWF/dl. Clinical Implica tions - Dogs with low plasma vWF concentrations may be homozygous for the defective allele, whereas dogs with midrange plasma VWF concentrat ions may be heterozygous. It can be difficult to distinguish normal ho mozygotes from heterozygotes if evaluation is based only on plasma VWF concentration.