[A family of pseudocholinesterase deficiency (silent type II)]

We report here a case of pseudocholinesterase (E.C. 3.1.1.8) deficiency, silent type II. The proband was a 29-year-old healthy man. His parents were cousins. A family study revealed that 9 out of 17 members of family investigated (paternal side 6, maternal side 3) concentrations. Serum cholinesterase activity were correlated well with serum albumin concentrations in both healthy people and patients with chronic liver diseases. The ratio of cholinesterase activity to albumin concentrations in serum was found more useful to detect heterozygous pseudocholinesterase deficiency than the serum cholinesterase activity alone. Both the dibucaine number and the fluoride number were within normal range in all family who showed low cholinesterase activity in serum. The amount of immunoreactive substance in serum against anticholinesterase antibody was normal in the proband as well as his family, while it was about twice of the value expected from their activity in those who had low ratio of serum cholinesterase activity to albumin concentrations. These results altogether suggested that the proband was a case of homozygous pseudocholinesterase deficiency, silent type II.