1. Overview and definition

Anorexia nervosa (AN), classified under “feeding and eating disorders” in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) by the American Psychiatric Association, is characterized by a distorted perception of body weight and shape and a pathological preoccupation with food and eating. The most common form is the restricting type (AN-R), in which food intake is severely limited. Another form is the binge–purge type (AN-BP), which involves recurrent self-induced vomiting and misuse of laxatives, diuretics, or enemas. AN leads to life-threatening weight loss; thus, careful physical management is essential. The peak age of onset is 14–18 years, affecting 0.5%–1.0% of adolescent females, although males are also affected, particularly in childhood. In prepubertal cases, clinicians should be alert to the frequent coexistence of neurodevelopmental disorders.

 2.  Symptoms

(1) Physical
Weight loss may cause muscle wasting, lanugo hair, amenorrhea or delayed menarche, and peripheral edema. Vital signs may show hypothermia, hypotension, and bradycardia. Other causes of weight loss must be ruled out using growth charts to visualize changes in height and weight. Differential diagnoses include brain tumors, endocrine disorders, gastrointestinal diseases, and maltreatment.

(2) Psychological
A disturbed body image and poor insight are common. Patients may fail to recognize their emaciated state. Emotional features may include aggression toward concerned family members, fear of abandonment, loneliness-driven compulsivity, restlessness, and self-disgust.

(3) Behavioral
Patients may suppress the urge to eat while interfering with family meals, sometimes encouraging others to eat. They may demonstrate heightened interest in cookbooks or cooking programs. In AN-BP, behaviors may include secret eating, food hoarding, binge eating followed by self-induced vomiting, and laxative misuse.

 3,  Diagnosis

Diagnosis is generally based on the DSM-5 criteria. AN is defined by persistent weight loss with distorted cognition of weight and body shape (drive for thinness or intense fear of weight gain) and pathological preoccupation with eating behaviors (avoidance of food, excessive exercise, etc.) lasting for >3 months. In Japan, the Eating Attitudes Test-26 questionnaire for children is useful for assessing eating behaviors and obtaining detailed information.

4.  Treatment and management

The initial goals of treatment are to correct disordered eating behaviors (psychoeducation) and address nutritional deficiencies (nutritional education). Normally, rapid intravenous rehydration should be avoided in outpatients because it may worsen edema and increase the risk of congestive heart failure. Outpatient treatment is generally feasible if the patient maintains ≥65%–70% of standard body weight; however, decisions depend on the individual case and the treating physician. Exercise restriction is required in cases of rapid weight loss (>1 kg per week) or excessive activity. Clarifying admission criteria early in treatment is important for later management. If outpatient weight falls <65% of standard body weight, admission should be explained as essential to prevent life-threatening deterioration and support recovery.

During the first week of refeeding, patients often experience intense anxiety about weight gain. Repeated reassurance is important, such as, “Eating this amount will not immediately cause weight gain.” Once physically stabilized, psychological therapies should be tailored to the child’s temperament, developmental stage, and family environment. Options include supportive psychotherapy, family-based treatment, CBT, sandplay therapy, play therapy, or art therapy, depending on the resources available at each institution and in consultation with psychologists.

5.  Complications and comorbidities

The most serious risk during refeeding is refeeding syndrome. This may lead to heart failure, arrhythmia, acute respiratory failure, lactic acidosis, impaired leukocyte function, coma, seizures, rhabdomyolysis, and sudden death. It can occur with oral, enteral, or parenteral nutrition. In patients who are severely underweight, nutritional support should begin at 20–30 kcal/kg/day (600–800 kcal/day) and be increased by 100–200 kcal every 2–3 days, with careful monitoring. Vital signs must be closely monitored, thiamine (vitamin B1) given before refeeding, and serum potassium, phosphate, and magnesium checked frequently with prompt correction (serum phosphate should ideally be maintained >2 mg/dL).

Long-term complications include short stature, reduced bone mineral density (osteoporosis), and impaired fertility. Even after acute treatment, long-term follow-up is required.

SUZUKI, Yuichi

Fukushima Medical University School of Medicine