Abstract Details

CLCN1 mutations can cause myotonia congenita, which typically results in clinical symptoms of muscle stiffness, myotonia, and weakness. 

Subject 1 presented with a chronic idiopathic sensorimotor polyneuropathy, bilateral foot drop, and severe muscle pain was found to have a pathogenic CLCN1 mutation, c.689G>A, *p.Gly230Glu when in his 30’s. Subject 2 presented with severe muscle pain, fatigue, and a mild idiopathic sensory neuropathy and was found to have a pathogenic CLCN1 c. 689 G>A (p.Gly230Glu) mutation when in his 30’s. Subject 3 had episodes of paralysis triggered by cold, diet, stress, bright lights, preceded by headaches and body pain, that were improved with potassium administration and had a pathogenic mutation CLCN1 c.2680C>T (p.Arg894) with symptoms starting in her late 60’s. Subject 4 presented with muscle pain, cramps, episodes of weakness with unknown triggers, fatigue, and a mild idiopathic sensorimotor neuropathy who had a pathogenic CLCN1 c.568_569delinsTC (p.Gly190Ser); the diagnosis was thought to be “CIDP” and was delayed until her 50’s. 

CLCN1 mutations can cause a wide spectrum and severity of presentations. In all four subjects, excruciating muscle pain was a common theme. As we learn more about these rare diseases, periodic paralysis and neuropathy can be added to the phenotypic spectrum of CLCN1 mutations, as can be evidenced in some subjects with this mutation. Further research is recommended.