BACKGROUND: Heterozygous KCNQ2 variants cause benign familial neonatal seizures and early-onset epileptic encephalopathy in an autosomal dominant manner; the latter is called KCNQ2 encephalopathy. No case of KCNQ2 encephalopathy with arthrogryposis multiplex congenita has been reported. Furthermore, early-onset scoliosis and opisthotonus have not been documented as characteristics of KCNQ2 encephalopathy. CASE REPORT: A male infant born with scoliosis and arthrogryposis multiplex congenita developed intractable epilepsy on the second day of life. At 4 months of age, he developed opisthotonus. The opisthotonus was refractory to medication in the beginning, and it spontaneously disappeared at 8 months of age. Whole-exome sequencing revealed a novel de novo heterozygous variant in KCNQ2, NM_172107.4:c.839A > C, p.(Tyr280Ser). CONCLUSIONS: Early-onset scoliosis, arthrogryposis multiplex congenita, and opisthotonus may be related to KCNQ2 encephalopathy.