Selenium responsive myositis during prolonged home total parenteral nutrition in cystic fibrosis.

The need for routine supplementation of total parenteral nutrition solutions with selenium (Se) has not been clearly defined. Although clinical selenium deficiency in patients on prolonged total parenteral nutrition has been reported, it is rarely observed in the United States. We report a 19-year-old woman with cystic fibrosis who developed muscle pain and weakness after 3 months on total parenteral nutrition which was not supplemented with Se. Coincident with her onset of symptoms, markedly elevated serum creatine kinase values were observed compared to baseline levels. Subsequent evaluations revealed undetectable (less than 0.02 microgram/ml) serum and urine Se levels in this patient. In addition, electromyographic evidence of myositis and nonspecific membrane irritability was documented. Therapy with oral Se rapidly reversed her symptoms and normalized with serum creatine kinase values over a 10-day period. Prolonged treatment with Se was required to achieve normal values of Se in the serum. Patients with severe pancreatic insufficiency, such as cystic fibrosis, may be at risk for clinical Se deficiency if on prolonged total parenteral nutrition without supplementation. Elevated creatine kinase levels should alert physicians to the possibility of Se deficiency in such patients.