A novel SCN9A gene variant identified in a Chinese girl with paroxysmal extreme pain disorder (PEPD): a rare case report

BACKGROUND: Paroxysmal extreme pain disorder (PEPD) is a rare autosomal dominant hereditary disease, characterized by paroxysmal burning pain in the rectum, eyes or mandible and autonomic nervous symptoms, including skin redness and bradycardia. PEPD is a sodium channel dysfunctional disorder caused by SCN9A gene variants. It occurs mainly in Caucasians and only one case has been reported in the Chinese population. Here, we report the second PEPD case in a Chinese indivisual. CASE PRESENTATION: A 2 years and 6 months old girl initially presented with non-epileptic tonic seizures at 7 days after birth. Her clinical symptoms in order of presentation were non-epileptic tonic seizures, harlequin color change and pain. Genetic analysis showed the patient carried a heterozygous variant c.4384T>A (p.F1462I) in the SCN9A gene, which was speculated to cause PEPD symptoms. After administrating carbamazepine, the symptoms were relieved and the patient's condition improved. However, the patient’s mother, who carries the same SCN9A variant as her daughter, only showed bradycardia and sinus arrest but no PEPD-related pain. CONCLUSIONS: This is the second PEPD case reported in the Chinese population. With the discovery of a novel variant in SCN9A, we expanded the genotype spectrum of PEPD. This is the first case suggesting that the clinical presentations of SCN9A-associated PEPD may show inter familial phenotypic diversity. In the future of clinical diagnosis, patients with triggered non-epileptic tonic seizures or pain and harlequin color change should be considered for PEPD and proper and prompt treatment should be given. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12920-022-01302-z.