Hyponatremia-associated rhabdomyolysis following exercise in an adolescent with cystic fibrosis

Adolescents with well-controlled cystic fibrosis, including good lung function and appropriate growth, commonly participate in competitive athletic activities. We present the case of an adolescent male with cystic fibrosis, hyponatremia, dehydration, and rhabdomyolysis after participating in football practice on a summer morning. The patient presented with severe myalgia and serum sodium of 129 mmol/L, chloride 90 mmol/L, and creatine phosphokinase 1146 U/L. Aggressive hydration with intravenous 0.9% saline resulted in clinical improvement with no renal or muscular sequelae. Health care providers need to educate patients with cystic fibrosis about maintaining adequate hydration and sodium repletion during exercise. Research is needed regarding the appropriate amount and composition of oral rehydration fluids in exercising individuals with cystic fibrosis, as the physiology encountered in these patients provides a unique challenge to maintaining electrolyte balance and stimulation of thirst.