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To describe the prevalence and characteristics of comorbidities in persons with rare epilepsies.Persons with rare epilepsies and caregivers of those affected were recruited through the Epilepsy Foundation and more than 30 rare epilepsy advocacy organizations affiliated with the Rare Epilepsy Network (REN). A web-based survey was conducted using a questionnaire consisting of core sections to collect data from affected persons on various aspects, including comorbidities. Comorbidity information was grouped into 15 classes, 12 of which had a stem question followed by detailed branch questions and 3 that were created from a combination of related questions.Of 795 persons with more than 30 different rare epilepsy diagnosis groups, one-half had ≥5 comorbidity classes and 97% were classified as complex chronic disease (C-CD). The highest number of comorbidity classes reported per person were persons with Aicardi syndrome, Phelan-McDermid syndrome (median, 7.0; IQR, 5.0-9.0), and tuberous sclerosis complex (median, 6.0; IQR, 4.0-8.0). The most common comorbidity classes were learning/developmental disability (71%), mental health issues (71%), sleep disorders (60%), brain abnormalities (52%), oral issues (49%), bone-joint issues (42%), hyper/hypotonia (42%), and eye-vision disorders (38%). The prevalence of brain abnormalities, hyper/hypotonia, eye, and cardiac disorders was significantly higher in persons first diagnosed with epilepsy at a younger age (9 months) than in those first diagnosed at an older age (P .05 for trend).Nearly all persons with rare epilepsies are medically complex, with a high prevalence of multiple comorbidities, especially those who were diagnosed with epilepsy in the first year of life. Comorbidities should be carefully considered in the diagnosis and management of persons with rare epilepsies.

Clinical genetic studies have shown that loss of Nav1.7 function leads to the complete loss of acute pain perception. The global deletion is reported lethal in mice, however, and studies of mice with promoter-specific deletions of Nav1.7 have suggested that the role of Nav1.7 in pain transduction depends on the precise form of pain. We developed genetic and animal husbandry strategies that overcame the neonatal-lethal phenotype and enabled construction of a global Nav1.7 knockout mouse. Knockouts were anatomically normal, reached adulthood, and had phenotype wholly analogous to human congenital indifference to pain (CIP): compared to littermates, knockouts showed no defects in mechanical sensitivity or overall movement yet were completely insensitive to painful tactile, thermal, and chemical stimuli and were anosmic. Knockouts also showed no painful behaviors resulting from peripheral injection of nonselective sodium channel activators, did not develop complete Freund’s adjuvant-induced thermal hyperalgesia, and were insensitive to intra-dermal histamine injection. Tetrodotoxin-sensitive sodium current recorded from cell bodies of isolated sensory neurons and the mechanically-evoked spiking of C-fibers in a skin-nerve preparation each were reduced but not eliminated in tissue from knockouts compared to littermates. Results support a role for Nav1.7 that is conserved between rodents and humans and suggest several possibly translatable biomarkers for the study of Nav1.7-targeted therapeutics. Results further suggest that Nav1.7 may retain its key role in persistent as well as acute forms of pain.