Last modified: 2018-09-09
Abstract
Introduction: Acquired Neuromyotonia (Isaac’s Syndrome) is the result of peripheral nerve hyperexcitability, which manifests as spontaneous muscle twitching (myokymia). It may be associated with cramps, pain, hypertrophy, weakness, wasting and sweating. Contactin-associated protein-like 2 and Leucine-rich, glioma inactivated 1 protein are proteins within the VGKC complex knownto be associated with neuromyotonia.
Objective: To describe three children with acquired neuromyotonia with CASPR2 and LGI1 Antibodies.
Case report: Three children (case 1: 13-year-old boy; case 2: 14-year-old boy; case 3: 4-year-old boy), presented with acute onset myokymia and pain in lower limbs. Case 3 in addition had significant muscle weakness. EMG showed peripheral nerve hyperexcitability ( in 2). All infectious, alternative inflammatory and neurometabolic aetiologies were ruled out with appropriate investigations.
All patients had positive serum antibodies to CASPR2 and LGI1. Two cases improved without immunotherapy; case 1 was treated with Carbamazepine and gabapentin while case 2 received no treatment. Case 3 was treated with steroids, immunoglobulins and methotrexate with improvement. However, symptoms recurred on discontinuation of immunotherapy and he remained immunotherapy-dependant. All were screened for occult malignancies which were negative.
Conclusion: This is the first report of acquired neuromyotonia in children associated with CASPR2 and LGI1 antibodies in serum. It remains underreported in children and although not fatal, can be disabling and affect quality of life. This condition may be associated with underlying tumors, (thymoma) which mandates investigation. It is amenable to symptomatic treatment ,some patients may undergo spontaneous recovery, while the severely affected may require long-term immunotherapy.