20-year-old woman with nausea and vomiting.

A 20-year-old woman was admitted to the hospital from the emergency department because of nausea, vomiting, and dehydration. She had no notable medical history and was taking no medications. During the previous 4 months, she had experienced intermittent nausea, vomiting, and increasing fatigue. Her symptoms had worsened during the 3 weeks before presentation, and she had sought treatment at an emergency department elsewhere 1 week before coming to our emergency department. At that time, she received intravenous hydration and was sent home with conservative treatment. She denied having abdominal pain, fever, loss of appetite, diarrhea, and headaches. However, she reported a 9-kg weight loss since her symptoms had begun. Her menstrual cycles were regular, and she denied purging behaviors, recent travel, or contact with other sick individuals. She was a nonsmoker, did not use alcohol, and denied illicit drug use. Her father had hypertrophic cardiomyopathy, but no other family members had known health problems. On admission, the patient was afebrile. Her supine heart rate and blood pressure were 104 beats/min and 90/60 mm Hg, respectively. While standing, her heart rate was 116 beats/min and her blood pressure was 70/50 mm Hg. She was alert, oriented, and appeared thin. Her mucous membranes were slightly dry and hyperpigmented. Examination of the neck revealed no lymphadenopathy. Heart sounds were normal, and no murmurs were detected. Lung examination yielded normal findings. Her abdomen was soft and nontender with no organomegaly. No abnormalities were identified on genital examination. Initial laboratory tests yielded the following results (reference ranges shown parenthetically): hemoglobin, 11.1 g/dL (12.0-15.5 g/dL); mean corpuscular volume, 84.9 fL (81.6-98.3 fL); white blood cell count, 6.7 × 10/L (3.5-10.5 × 10/L) with normal differential; platelet count, 235 × 10/L (150-450 × 10/L); sodium, 129 mEq/L (135145 mEq/L); potassium, 5.5 mEq/L (3.6-4.8 mEq/L); glucose, 99 mg/dL (70-100 mg/dL); bicarbonate, 20 mEq/L (22-29 mEq/L); chloride, 100 mEq/L (100-108 mEq/L); blood urea nitrogen, 27 mg/dL (6-21 mg/dL); creatinine, 1.0 mg/dL (0.7-1.2 mg/dL); serum osmolality, 277 mosm/kg H 2 O (275-295 mosm/kg H 2 O); and urine osmolality, 593 mosm/kg H 2 O (300-800 mosm/kg H 2 O). Electrocardiography revealed sinus tachycardia. Liver function test results were within normal limits.