Recurrent nocturnal tongue biting in a child with hereditary chin trembling.

A 13-month-old boy presented with repeated episodes of tongue biting during sleep. On evaluation, he was found to have hereditary chin trembling, a rare autosomal dominant condition characterized by continuous or intermittent tremulous activity of the mentalis muscle. This is the first report of this kind from India. The tongue biting appeared to be the result of parasomnia. Treatment with clonazepam was very effective; it completely ameliorated the symptom of tongue biting but had no effect on chin trembling.