Genetic Analysis of Low Cholinesterase Activity in a Patient

Abstract

In the present study, we present a patient with congenital hypothyroidism accompanied by low cholinesterase activity in serum. The proband is a 48-year-old Japanese woman. The cholinesterase activity in the proband was consistently decreased to 5% of the reference range.The full coding region of the cholinesterase gene (exon 2-4) was amplified and the amplified PCR products were sequenced by the dideoxy cycle sequence method. A genetic mutation of A to G transition was identified in the exon 2, resulting in a missense mutation from Glu (GAA) to Gly (GGA) at codon 90 of exon 2. This patient was homozygous for this substitution and the common polymorphism site of codon 539 in exon 4 was Thr (ACA), indicating this allele is Kvariant. Although we could not investigate the mRNA amount in liver cells, we tentatively concluded that the proband had no cholinesterase activity in serum due to abnormal secretion from the liver cells due to the missense mutation.