• Anamarija Meglič, Mirjana Perkovič-Benedik, Katarina Trebušak Podkrajšek, and Sara Bertok.
• Department of Pediatric Nephrology, Division of Pediatrics, University Children's Hospital, University Medical Centre Ljubljana, Bohoričeva ulica 20, 1000, Ljubljana, Slovenia, anamarija.meglic@mf.uni-lj.si.
• Pediatr. Nephrol. 2014 Sep 1;29(9):1643-6.

BackgroundParoxysmal extreme pain disorder (PEPD) is a rare autosomal dominant pain disorder linked to a mutation in the SCN9A gene, which encodes voltage-gated sodium channel Nav1.7. Abnormal pain sensitivity occurs because of changes in the properties of voltage-gated sodium channels. Different mutations in SCN9A and a spectrum of clinical expressions have been described.Case Diagnosis/TreatmentHere we describe a 3-year-old child with a rare clinical picture of PEPD. Extremely painful voiding had been present since the child's birth. The diagnosis was confirmed by the detection of a heterozygous pathogenic mutation in the SCN9A gene, c.554G>A (p.Arg185His) inherited paternally. The same mutation was also found in the girl's father, who has occasionally had some pain in his jaw while yawning since childhood. Significant reduction of the pain was achieved with carbamazepine.ConclusionsThe case is interesting because the same mutation as that found in the girl and her father has been found in patients with small fiber sensory neuropathy. These data do not correlate with the clinical picture of our case and her father, but intra- and interfamily phenotypic diversity in symptoms associated with a gain-of-function variant of Na(V)1.7 are also described and may explain our case.

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