Abstract
This case report describes the management of a 49-year-old female with restricting-type anorexia nervosa and excessive compulsive exercising associated with rhabdomyolysis, high levels of serum creatine kinase (CK) (3,238 U/L), and marked hyponatremia (Na+: 123 mEq/L) in the absence of purging behaviours or psychogenic polydipsia; it is the first case report to describe exercise-associated hyponatremia in a patient with anorexia nervosa. The patient, who presented with a body mass index (BMI) of 13.4 kg/m2, was successfully treated by means of an adapted inpatient version of an enhanced form of cognitive behavioural therapy (CBT-E). Within a few days, careful water restriction, solute refeeding, and the specific cognitive behavioural strategies and procedures used to address the patient's excessive compulsive exercising and undereating produced a marked reduction in CK levels, which normalised within one week. Exercise-associated hyponatremia also gradually improved, with serum sodium levels returning to normal within two weeks. The patient thereby avoided severe complications such as cerebral or pulmonary oedema or acute renal failure and was discharged after 20 weeks of treatment with a BMI of 19.0 kg/m2 and improved eating disorder psychopathology.
Highlights
Rhabdomyolysis, muscle injury associated with increased serum creatine kinase activity (CK), has been widely reported in those who practice sports [1] and may occur in conjunction with exercise-associated hyponatremia [2]
An association between hyponatremia and rhabdomyolysis has previously been reported in populations of athletes [2,3,4, 11], to our knowledge this is the first time that a case of both being induced by excessive exercising in a female patient with anorexia nervosa has been described
There are three main mechanisms involved in hyponatremia during exercise: (i) unequal replacement of salt and water lost in sweat; (ii) syndrome of inappropriate antidiuretic hormone release; and (iii) excess fluid intake [2]
Summary
Rhabdomyolysis, muscle injury associated with increased serum creatine kinase activity (CK), has been widely reported in those who practice sports [1] and may occur in conjunction with exercise-associated hyponatremia [2]. Exercise is defined as “excessive” when it significantly interferes with important activities, occurs at inappropriate times or in inappropriate settings, or continues despite injury or other medical complications [16]. In such patients, generally females, excessive exercising often results in overuse injuries, bone fractures [17], and cardiac complications [18]. Some reports have described the occurrence of rhabdomyolysis in patients with anorexia nervosa [22,23,24,25], but indications as to how best to manage the condition and prevent the development of severe complications such as acute renal failure and cerebral and pulmonary oedema are not available in the existing literature [25]. We describe here a case of a patient with restricting-type anorexia nervosa and concomitant rhabdomyolysis and hyponatremia, likely the consequence of excessive compulsive exercising, successfully managed by means of fluid restriction and solute repletion associated with an adapted inpatient version of an enhanced form of cognitive behavioural therapy (CBT-E)
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