OBJECTIVETo analyze the phenotypes and proline-rich transmenbrane protein 2 (PRRT2) gene mutations in patients of infantile convulsions with paroxysmal choreoathetosis (ICCA).

METHODSClinical data were collected from ICCA patients and their family members. Genomic DNA was extracted from peripheral blood samples with standard protocol. Mutations of PRRT2 were screened using PCR amplification and Sanger sequencing.

RESULTSEleven families and one sporadic case with ICCA were recruited in this study. In 11 ICCA families, 49 family members were affected, of which 15 individuals had benign infantile convulsions (BIC) alone, 18 individuals had only paroxysmal kinesigenic dyskinesia(PKD), and 16 individuals had BIC followed by PKD. The seizure onset age of infantile convulsions was between 3 and 12 months. The onset age of PKD was ranging from 5 to 17 years old. Four affected members in two ICCA families had PKD or ICCA co-existing with migraine. The one sporadic ICCA case had afebrile seizures between 3.5 and 4 months, and developed paroxysmal twists of limbs after 3 years and 9 months of age. He had good response to treatment with oxcarbazepine at the age of 4 years and 10 months. PRRT2 mutations were identified in all 11 ICCA families. The most common mutation, c.649_650insC (p.R217PfsX8), was detected in 6 of the 11 families (54.5%). PRRT2 mutation (c.649_650insC) was also found in the sporadic ICCA case, and was identified as de novo mutation.

CONCLUSIONThe phenotype of PKD in ICCA families occurred in childhood or adolescence. Few affected members in some ICCA families may have migraine. PRRT2 is the causative gene of ICCA and the mutation c.649_650insC was the hotspot of PRRT2 mutations. PRRT2 mutation was also found in sporadic case with ICCA.