AssessmentsEating disorders: Pathology review
USMLE® Step 1 style questions USMLE
A 27-year-old woman comes to the physician to discuss her appetite. The patient tells the physician that for the last one and a half months she has been eating ice “nearly every day,” stating that she has intense cravings for it. Her appetite is otherwise normal, and she feels her weight has been stable over this time period. Apart from these cravings, she says her life is “completely normal,” and that she functions well at her job and is taking care of her 5-year old son. She does not have any history of mental illness. Family history is noncontributory. Which of the following is most likely to be found on further evaluation?
Content Reviewers:Antonella Melani, MD
23 year old Adeline is brought to the emergency department by her peers after fainting in the college cafeteria. Upon examination, her pulse is 47/min, and her blood pressure is 89 over 48 mmHg. In addition, her height is 162 cm or 5 ft 4 in, and she weighs 45.4 kg or 100 lbs. Adeline mentions that she considers herself fat, which is why she’s been trying to lose weight, and admits to purging or making herself vomit whenever she eats a large meal. On further questioning, she tells you that her last menstrual period was more than 3 months ago. You decide to run a urine pregnancy test, which comes back negative. The next day, you see 17 year old Emmanuel, who is brought to the clinic by his mother, who saw him forcibly vomit after lunch. Emmanuel states he has recently been very anxious about the college entrance exam and that he feels like vomiting is the only thing in life that he can control. His vitals show no abnormalities, his height is 185 cm or 6 feet 1 in, and he weighs 72 kg or 158 lbs. Physical examination shows decaying enamel on teeth, as well as thickened skin around the knuckles of his right hand.
Based on the initial presentation, both Adeline and Emmanuel have some form of eating disorder. Eating disorders are mental health disorders in which an individual exhibits abnormal eating behaviors that negatively impact their physical and mental health. They are quite common, especially among young females who struggle with low self-esteem and the social pressure to look a certain way. However, remember that they can affect anybody, regardless of their sex, age, and social background. For your exams, the most common eating disorders include anorexia nervosa, bulimia nervosa, binge eating disorder, and pica.
Okay, let’s start with anorexia nervosa. This is characterized by a constant fear of gaining even the slightest amount of weight, associated with a distorted body image, with individuals often believing that they are overweight, while actually being underweight. To be more specific, their Body Mass Index or BMI is lower than 18.5.
Now there are two main types of anorexia. One is the binge-eating and purging type, where individuals eat large amounts of food in one sitting and then purge that food through self-induced vomiting or by taking laxatives or diuretics, and this occurs recurrently for at least 3 months. The other is the restricting type, where people reduce the amount of food they eat or over-exercise in order to lose weight without any purging.
Now, individuals affected by anorexia nervosa literally starve themselves. Over time, this can result in several complications, which can end up being clues to the diagnosis. At first, there’s muscle tissue loss throughout the body, which often manifests as fatigue, but can also lead to difficulty breathing due to a weak diaphragm. Even the heart can become weaker, and this can manifest as bradycardia, meaning less than 60 heartbeats per minute, and hypotension, meaning a blood pressure below 90 over 50 mmHg, as well as orthostatic hypotension, which is when blood pressure falls when a person goes from a lying down position to a standing position. For those who menstruate, another key symptom is amenorrhea, where either the normal menstrual cycle stops or menstruation doesn’t start by age 15. Prolonged food restriction, as well as taking laxatives frequently, can also make the gastrointestinal tract unable to handle normal meals, which can cause terrible bloating, nausea, and constipation. Individuals with the binge-eating and purging type might also have halitosis or really bad breath from repeated vomiting.
Also, the bone marrow can start shutting down because of the lack of essential nutrients, so you get neutropenia, or fewer white blood cells which leads to a dampened immune response, anemia or fewer red blood cells which leads to lower energy levels, and thrombocytopenia or fewer platelets which leads to easy bleeding and bruising. Anorexia can also cause osteoporosis, where the bones become weak and susceptible to fractures. The skin may also become dry, scaly, and covered by brittle or soft hair, called lanugo. And that’s actually high yield! Finally, it can affect the brain, causing symptoms like confusion, irritability, or restlessness, as well as depression or anxiety. Ultimately, individuals affected by anorexia nervosa may die from these complications or commit suicide.
Standard treatment of anorexia nervosa involves nutritional rehabilitation and psychotherapy like cognitive behavior therapy, which aim at restoring and stabilizing a normal weight and eating patterns, as well as changing their thoughts and beliefs about body weight and shape. In addition, individuals with severe depression or anxiety can be treated with antidepressants, such as a selective serotonin reuptake inhibitor or SSRI for short. However, for your test, remember that the antidepressant bupropion is contraindicated because it is associated with a higher incidence of seizures in individuals with eating disorders.
Now, what’s extremely important to know for your test is that feeding an individual too rapidly or aggressively can lead to the refeeding syndrome. That’s when the sudden intake of large amounts of food causes lots of insulin to be released at once, resulting in sudden electrolyte shifts, since insulin makes the cells take in potassium, magnesium, and phosphate. So, lab tests will show hypokalemia, hypomagnesemia, and hypophosphatemia. Keep in mind that, when the serum levels of potassium fall below 3 millimoles per liter, it can lead to weakness, seizures, rhabdomyolysis, impaired respiratory function, cardiac arrhythmias, heart failure, and even death. So, remember that refeeding syndrome can be life-threatening! Next is bulimia nervosa, which is characterized by cycles of binge eating, meaning rapid, out-of-control eating past the point of fullness or comfort, followed by compensatory purging to prevent weight gain, either by self-induced vomiting, over-exercising, or taking laxatives or diuretics. To fit the diagnosis, remember that these cycles of binging and purging must repeat consistently at least once a week for a period of 3 months, but sometimes can happen as often as multiple times per day. Often, the trigger for binging and purging is an emotional stressor that’s not necessarily related to weight or body image, for example failing to reach a certain goal. For your exams, you should definitely be able to distinguish bulimia from anorexia nervosa. So, the main distinction is that individuals with bulimia usually have a BMI that’s normal or high, so it’s over 18.5, whereas individuals with anorexia typically have a BMI that's lower than 18.5. Sometimes, though, individuals may start with bulimia, and then develop anorexia over time, and vice versa.
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