Prolonged muscle paralysis in a healthy individual may be caused by:

Pseudocholinesterase deficiency is an inherited enzyme abnormality that results in abnormally slow metabolic degradation of exogenous choline ester drugs such as succinylcholine and mivacurium. If there is a deficiency in the plasma activity of pseudocholinesterase, prolonged muscular paralysis may occur, resulting in the extended need for mechanical ventilation. A variety of pathologic conditions, physiologic alterations, and medications also can lower plasma pseudocholinesterase activity. Succinylcholine apnea may be seen suddenly in healthy individual due to deficiency of pseudocholinesterase .