Transient neonatal myasthenia gravis in a baby born to a mother with new-onset anti-MuSK-mediated myasthenia gravis.

We describe a 30-year-old pregnant woman with undiagnosed weakness who delivered a severely weak neonate. Subsequent workup of the mother revealed myasthenia gravis with muscle-specific kinase antibodies. The infant responded to intravenous immunoglobulin and symptoms normalized.

Diffusely increased insertional activity: "EMG disease" or asymptomatic myotonia congenita? A report of 2 cases.

The term "EMG disease" is used by some to describe the unexpected finding of diffusely increased insertional activity on needle electromyography in an otherwise asymptomatic person. The cause is unknown, but it has been hypothesized that these patients actually have a subclinical myotonic disorder. We describe 2 patients with diffusely increased insertional activity on electromyography who had mutations of the CLCN1 gene associated with myotonia congenita.