Cholinesterases silent variants

Mivacurium block is significantly prolonged in patients with inherited homozygous silent or atypical plasma cholinesterase variants the... 

However, the situation concerning silent cholinesterase variants is rather complex, and some conclusions that have been drawn may be incorrect. Some reports have stated that no enzyme activity and no cholinesterase-like protein could be detected in the silent sera studied, but it is clear that whether or not any cholinesterase activity is observed depends on a number of factors. If the gene and all of its alleles are absent, no protein product will be produced, and the phenotype will be silent under all assay conditions. The same holds true if a gene is present... 

Additional evidence concerning the heterogeneity of homozygous silent sera has been reported by Lubin et al. (L36), who studied two patients whose silent cholinesterases were different from one another and were unlike any of those reported by Rubinstein et al. (Rll). Two other patients with dissimilar silent cholinesterases were studied by Das (D2). Arnason et al. (All) have also reported on a possible nearly silent cholinesterase variant. It is difficult to compare these results with those of previous workers because of differences in experimental procedures. 

In summary, the situation concerning the silent or near silent cholinesterase variants is complex. There are at least three cholinesterase variants which are most importantly characterized by a severe quantitative deficiency in cholinesterase activity. Family studies indicate that these three variant are alleles of the gene for usual cholinesterase, Ey, although more studies are needed in this area. There are indications that a variety of other near-silent cholinesterase subtypes exist. Cases of true silence, because the gene is absent or because it produces no protein product, appear to be very rare. Many cases reported to have no cholinesterase activity have subsequently been found to have at least a trace of activity when studied imder more sensitive assay conditions or with a different substrate. 

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