Infantile Convulsion Choreoathetosis Syndrome in a Hong Kong Chinese Family

Abstract

Background: Infantile convulsion choreoathetosis syndrome (ICCA) is inherited as an autosomal dominant trait. Seizures appear at 3-12 months, and are partial and may secondarily generalize. Seizures soon stop but paroxysmal choreoathetosis starts between 5-9 years. Genetic studies reveal evidence of linkage to the pericentromeric region of chromosome 16. No causative gene has been found to date. The SLC5A11 gene, encoding a sodium/glucose cotransporter and located in 16p12-p11 region, is postulated to be a candidate. However, no pathogenic mutation was found so far in families with ICCA. We report a Chinese family with ICCA syndrome. Method and Result: CWP was a 30-month-old boy who presented with 3 episodes of generalized tonic clonic convulsions, which may or may not be provoked by upper respiratory tract infection, between 6 and 7 months old. Physical examination and EEG was unremarkable. He was treated with low-dose valproate and remained seizure free since then. At 30 months, he had mild developmental language delay. His maternal 1st cousin, CWH, was a 16-year-old boy. He had multiple generalized tonic clonic seizures associated with upper respiratory tract infection at 11 months old. He was put on a week course of anticonvulsant then remained seizure-free. Since the age of 10, he had recurrent episodes of choreoathetosis involving all the 4 limbs. He had normal intelligence with normal neurological examination. The diagnosis of paroxysmal kinesigenic dyskinesia (PKD) was subsequently made. Once diagnosed, low-dose carbamazepine induced remission. 4 other family members had infantile convulsions with complete remission after few years of age. They did not have PKD. 2 more had transient PKD without infantile convulsion. They were not on treatment. Direct sequencing of the 15 coding exons of SLC5A11 gene from CWP, his mother and his normal sister did not show any coding mutations or splicing junction changes, indicating that this gene may not be involved in this family. Conclusion: Our family shows typical features of ICCA syndrome. Accurate diagnosis is very important as it is amenable to low-dose anticonvulsant treatment and in general of good prognosis. In agreement with other studies, our family may not be related to SLC5A11 gene mutation. Further linkage study is in progress.