CLCN1 mutation and right foot drop
Objective: To expand the clinical spectrum of CLCN1 mutations.
Background: It has been known that CLCN1 mutations can cause myotonia congenita, which typically results in clinical symptoms of muscle stiffness, myotonia, and weakness.
Methods: A 58 year old proband had genetic, clinical, radiographic and electrophysiological testing.
Results: A very healthy 58 year old athletic gentleman presented with painless right foot drop. Electrophysiological testing revealed a right peroneal neuropathy with no myotonia. Genetic testing revealed a pathogenic CLCN1 mutation, c.950G>A, (p.Arg317Gln). Extensive laboratory work up including CK, acetylcholine receptor antibody, voltage gated calcium channel antibody, GM1 antibody, paraneoplastic panel, MRI imaging of the lumbar spine was unrevealing.
Conclusion: CLCN1 mutations can cause a wide spectrum and severity of presentations. In our subject, a an isolated right peroneal neuropathy is a rare presentation of a CLCN1 mutation.