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Author [[PageAuthor::Serge Korjian, M.D., Gonzalo A. Romero, M.D. [1] (Reviewed by Will Gibson and Serge Korjian)]]
Exam Type USMLE Step 1
Main Category Behavioral Science/Psychiatry
Sub Category General Principles
Prompt A 17-year-old woman is brought to the outpatient clinic by her mother because she is refusing to eat and is exercising more than usual. She has earned several awards because of her athletic skills in the past, and is extremely competitive in school. Five months ago her parents divorced. Shortly thereafter, the patient started a special diet and she has lost approximately 25 pounds. Her mom has tried to enforce a regular diet with sufficient calories, but the patient is reluctant to increase her caloric intake. She reports a strong fear of gaining weight and feels fat in front of the mirror. The patient reports that she stopped having a menstrual cycle 6 weeks ago. Her heart rate is 78/min, blood pressure is 123/80 mm Hg, temperature is 37°C (98.6 °F), and BMI is 16.5 kg/m2. Examination reveals hair thinning, dry skin with fine hair over the body, and mild parotid swelling. What is the most likely diagnosis?
Answer A Post-traumatic stress disorder (PTSD)
Answer A Explanation [[AnswerAExp::Post traumatic stress disorder (PTSD) is characterized by the re-experiencing of a stressful event (flashbacks) and the avoidance of associated stimuli. Patients with PTSD often experience sleep disturbances, nightmares, irritability, and inability to concentrate. A diagnosis of PTSD requires that symptoms last more than one month, if symptoms last less than one month the diagnosis of "acute stress disorder" is made. PTSD usually presents after a stressful event severe enough to disrupt one's normal coping mechanisms. Common causes of PTSD include witnessing or being subject to extreme violence or rape.]]
Answer B Obsessive compulsive personality disorder (OCPD)
Answer B Explanation [[AnswerBExp::Obsessive compulsive personality disorder (OCPD) is a cluster B personality disorder characterized by a lifelong pattern of perfectionism that extends to all areas of life (pervasive). This patient might present traits of OCPD, but her presentation is not as intense or chronically present to be considered diagnostic of OCPD. Furthermore, excessive calorie restriction and weight loss constitute the prevailing medical theme in this patient, and these behaviors are not generally characteristics of OCPD patients.]]
Answer C Anorexia nervosa
Answer C Explanation [[AnswerCExp::Anorexia nervosa is an eating disorder frequently seen in female teenagers and young female adults. It is characterized by a restriction in caloric intake that causes significant weight loss 15 to 20% below ideal weight with a BMI <17.5 kg/m2.]]
Answer D Bulimia nervosa
Answer D Explanation [[AnswerDExp::Bulimia is an eating disorder that involves binging and purging behaviors defined as voluminous ingestion of food followed by vomiting, laxative use, dieting pills or exercise. On physical exam these patients often have signs of vomiting such as callous on hands, enlarged parotids and other glands, dental cavities, esophageal tears or esophagitis. BMI usually stays normal or above normal. Treatment usually includes counseling, but may involve SSRIs, imipramine, or more structured rehabilitation.]]
Answer E Obsessive compulsive disorder (OCD)
Answer E Explanation [[AnswerEExp::Obsessive compulsive disorder (OCD) is a sub-type of anxiety disorder characterized by intrusive thoughts that produce uneasiness and repetitive behaviors aimed at reducing the associated anxiety. OCD patients classically have focal obsessions and are aware that their behavior is not normal. Both these traits help distinguishing it from obsessive personality disorder which is lifelong and pervasive.]]
Right Answer C
Explanation [[Explanation::Most of this patient's symptoms are consistent with a diagnosis of anorexia nervosa, including the constant fear of gaining weight, body image disturbance, restriction in caloric intake, and excessive exercise. Approximately half of anorexia nervosa patients develop bulimia-like binging and purging behaviors. Depression is also common among anorexia patients. On physical exam, patients may have lanugo or baby-like hair, dental cavities due to vomiting, and possibly could have a lower Tanner stage if the disease starts in adolescence. Treatment usually consists of psychotherapy and counseling to stabilize body weight and improve body image. Mirtazapine is an antidepressant commonly suggested for anorexia treatment on the USMLE, as it increases appetite as a side effect.

Several important characteristics help distinguish anorexia from bulimia. Anorexia nervosa causes low BMI and amenorrhea due to the strict caloric intake. Patients with anorexia most often lack insight and are not perturbed by their symptoms making treatment more challenging. Conversely, bulimia nervosa is a syndrome that is characterized by episodes of binging and purging, often by induced vomiting or laxative abuse. These patients tend to have a normal or high BMI and often view their symptoms as excessive and abnormal. They may display signs of vomiting induction such as callous on fingers, halitosis, enlarged parotids, and dental cavities. While this patient has signs of frequent vomiting, her low BMI, caloric restriction and excessive exercise make anorexia the more likely option.

In both anorexic and bulimic patients, cardiac complications may arise due electrolyte disturbances and consequent conduction defects. A small percentage of these patients can die from fatal arrhythmias.
Educational Objective: Anorexia nervosa is an eating disorder characterized by low BMI, amenorrhea, dry skin, hair loss, and lanugo.
References: First Aid 2014 page. 512]]

Approved Yes
Keyword Eating, Eating disorder, Anorexia, Bulimia, Psychiatry, Behavioral Science
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