Revisiting the clinical impact of variants in EFHC1 in patients with
different phenotypes of genetic generalized epilepsy
Abstract
The most common form of genetic generalized epilepsy (GGE) is juvenile
myoclonic epilepsy (JME), which accounts for 5 to 10% of all epilepsy
cases. The gene EFHC1 is associated with JME. However, it remains
debatable whether testing for EFHC1 mutations should be included in the
diagnostic epilepsy gene panels. To investigate the clinical utility of
EFHC1 testing, we studied 125 individuals: 100 with JME and 25 with
other GGEs. We amplified and sequenced all EFHC1 coding exons. Then, we
applied a revised version of the American College of Medical Genetics
and Genomics (ACMG)/Association for Molecular Pathology(AMP) guidelines
to predict the pathogenicity and benign impact of the variants. Mutation
screening revealed 11 missense variants in 44 probands with JME (44%)
and in 1 of the 7 individuals with generalized tonic clinic seizures on
awakening (14%). Overall, only the variant c.685T>C was
strictly classified as ‘pathogenic’ (1/11, 9%), five variants were
classified as ‘benign’ (45%), and the remaining five (45%) were
considered variants of uncertain significance (VUS). There is currently
a limitation to test for genes that predispose an individual to complex,
non-monogenic phenotypes. Thus, we consider EFHC1 to be a risk factor
for JME but not currently useful for clinical purposes.