Fenoterol precipitating myotonia in a minimally affected case of recessive myotonia congenita.

Fenoterol is used in patients with premature labor to delay delivery. A young women treated with fenoterol developed severe generalized myotonia. Symptoms disappeared after medication had been stopped. In a later study myotonic discharges were found electromyographically in the muscles of the patient and her brother. Both suffered from subclinical recessive myotonia congenita (Becker). A heterozygous manifestation may be supposed.