Acute postasthmatic amyotrophy is a rare condition, previously reported in only 26 cases. It is characterized by a sudden onset of a flaccid paralysis of an arm or a leg with completely preserved sensibility, about 1 week after an asthmatic attack. The cause is probably due to a lesion of the anterior horn of the spinal cord, but evidence indicates a more widespread pathological process. The etiology is unknown, but infectious or immunological mechanisms are likely.