A 21-year-old woman comes to the office due to constipation and vague abdominal pain. She says, "For the last few months I have felt bloated and my stomach doesn't feel right." Review of systems is notable for irregular menses and occasional fatigue. Medical history is significant for a broken femur at age 6 but is otherwise noncontributory. Family history is significant for Graves disease in her father and primary myelofibrosis in her paternal grandmother. The patient smokes a pack of cigarettes daily and drinks wine when relaxing with friends. She does not use illicit drugs. Temperature is 37.2 C (99 F), blood pressure is 90/60 mm Hg, pulse is 118/min, and respirations are 16/min. BMI is 25.6 kg/m². Physical examination shows eroded enamel of the teeth.Laboratory results are as follows: Which of the following is the most likely cause of this patient's condition?

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11ec160b_360b_6320_9249_65a75bd76f2b_MD0001_00 This patient's hypotension, tachycardia, dental erosion, and electrolyte abnormalities (eg, hypokalemia, hypochloremia, elevated bicarbonate [likely due to metabolic alkalosis]) are consistent with self-induced vomiting, suggesting a diagnosis of bulimia nervosa (BN). Chronic vomiting can also result in calluses on the dorsum of the hands (Russell sign) and enlarged parotid glands with resultant increased salivary amylase. Patients with BN are excessively preoccupied with their weight and shape and engage in repeated episodes of binge eating and inappropriate compensatory behaviors (eg, vomiting, laxatives, diuretics, fasting, excessive exercise) to prevent weight gain. Other common signs of BN include dry skin, menstrual irregularities, abdominal bloating, and constipation. (Choice A) Serum amylase, which does not typically differentiate between salivary and pancreatic origins, can be elevated in both pancreatic disease and BN; however, lipase would also be significantly increased in pancreatic disease, whereas this patient has increased amylase alone. Acute pancreatitis commonly presents with pain and an acute abdomen. (Choice B) With heavy alcohol use, expected findings would include elevated liver enzymes and other signs suggestive of abuse and dependence (eg, inability to control drinking, use in hazardous situations, tolerance, withdrawal symptoms). (Choice D) Hypothyroidism is characterized by weakness, fatigue, cold intolerance, constipation, weight changes, menorrhagia, dry skin, and bradycardia. It would not explain this patient's tachycardia, dental erosion, hypokalemic metabolic alkalosis, or hyperamylasemia. (Choice E) Irritable bowel syndrome is a functional gastrointestinal disorder characterized by chronic abdominal pain, constipation, and/or diarrhea. It is a diagnosis of exclusion and would not explain this patient's physical examination and laboratory findings. (Choice F) Sjögren syndrome, an autoimmune disorder mainly affecting women, presents with dry eyes and a dry mouth. Lack of normal saliva production can lead to enlarged salivary glands and dental caries. Sjögren syndrome would not explain this patient's hypokalemic metabolic alkalosis. Educational objective: Bulimia nervosa is characterized by episodes of binge eating and compensatory weight-reduction behaviors. Signs of self-induced vomiting include hypokalemia, metabolic alkalosis, parotid gland enlargement, dorsal hand calluses, and dental erosion. __________ References: Bulimia nervosa - medical complications. (http://www.ncbi.nlm.nih.gov/pubmed/25866627) Initial evaluation, diagnosis, and treatment of anorexia nervosa and bulimia nervosa. (http://www.ncbi.nlm.nih.gov/pubmed/25591200)

A 21-Year-Old Woman Comes to the Office Due to Constipation