DIFFERENTIAL DIAGNOSIS BY AGE It is particularly important to recognize potentially life-threatening causes of weight loss in children in the emergency department The emergency provider must take into account the age of the patient in order to create a differential diagnosis that focuses on the most likely life-threatening causes of weight loss in the patient’s age group ( Table 83.3 ) See Figure 83.1 for a clinical decision algorithm to aid in the identification of life-threatening causes of weight loss in children Infants In infants, several life-threatening diseases need to be considered in the differential diagnosis of weight loss ( Table 83.3 ) Congenital adrenal hyperplasia (CAH) is a dangerous condition in infants and may be fatal CAH may present with severe vomiting, weight loss, hyperkalemia, hyponatremia, and metabolic acidosis Ambiguous genitalia in female infants may offer a clue to the diagnosis but may not be present Pyloric stenosis is another potentially lethal cause of weight loss in infants, and is characterized by forceful or projectile vomiting and acute weight loss in an infant with vigorous feeding Bilious emesis in an infant suggests possible malrotation and midgut volvulus An infant with vomiting and anorexia, altered mental status, and ill-appearance raises concern for a possible inborn error of metabolism, especially in the setting of metabolic acidosis, hypoglycemia, liver dysfunction, or hyperammonemia Another lifethreatening cause of weight loss in infants is abuse or neglect If suspected, emergency providers may need to contact a social worker and child protective services and consider further work-up to look for other injuries (e.g., computed tomography imaging of the head, skeletal survey, and targeted laboratory testing such as hemoglobin/hematocrit, AST, ALT, amylase, and lipase)