2021 Volume 70 Issue 1 Pages 132-137
Prekallikrein (PK) is a type of serine protease synthesized in the liver, and it is involved in intrinsic clotting reaction, vasodilation and hyperfibrinolysis. Because congenital PK deficiency has few clinical symptoms such as bleeding, it is often found accidentally. We encountered a case of congenital PK deficiency in a male patient who is in his 50s. He visited our hospital for prostate cancer surgery, and a screening test showed extreme prolongation of the activated partial thromboplastin time (APTT) of 178.7 s. He had no bleeding symptoms and no relatives with bleeding tendency. A cross-mixing test was performed to find the cause of APTT prolongation, and we obtained a waveform of the factor deficiency pattern. However, all intrinsic clotting factors showed normal patterns. Therefore, we measured the activities of PK and high-molecular-weight kininogen (HMWK), which are contact factors, by the one-stage coagulation method. Results showed that the PK activity was 1.5%, and the HMWK activity was 74.5%; the PK activity was significantly decreased. Eventually, he was diagnosed as having congenital PK deficiency. In gene analysis, heterozygous missense mutations were found at three locations: exon 5, exon 9 and exon 14. The effect of this mutation on PK activity has not been reported. From this experience, we thought that this disease should be considered as a cause of unknown APTT prolongation. In addition, the pattern of a cross-mixing test is very useful for diagnosing this disease.
