Comparison of disease severity in adolescents with anorexia nervosa and atypical anorexia nervosa

Although atypical anorexia nervosa (AAN) is as common as anorexia nervosa (AN) it is often underrecognized due to normal or above-normal weight at presentation. We aimed to compare disease characteristics between adolescents with AN and AAN using a comprehensive panel of anthropometric, vital-sign, biochemical, and clinical variables.

A retrospective chart review was performed for adolescents aged 12-18 years diagnosed with AN and AAN according to DSM-5 criteria. Anthropometric, vital-sign, and laboratory measurements, and hospitalization data at presentation were recorded. The weight loss percentage and rate, and vital instability data were categorized using the SAHM 2022 guideline.

Of 230 adolescents, 82 had AN (35.7%) and 148 had AAN (64.3%). No significant differences were found in terms of weight loss percentage (p = 0.453) or rate (p = 0.348). While the hypotension (p < 0.001) and hypothermia (p = 0.017) rates were significantly higher in AN, bradycardia and orthostatic changes did not differ. AN showed higher rates of elevated creatinine (p = 0.006), hyponatremia (p = 0.006), hypokalemia (p = 0.017), and hypercholesterolemia (p = 0.003), and hypogonadism (p < 0.001). Other laboratory abnormalities did not differ between the two groups. Hospitalization rates and time for vital instability recovery were similar between AN and AAN. However, adolescents with AN were eight-fold more likely to experience refeeding syndrome (p = 0.002).

While adolescents with AN demonstrate more overt physiological compromise, those with AAN demonstrated comparably significant medical severity. These findings underscore that body weight alone is a misleading indicator of disease severity. Reducing weight bias and improving clinician awareness are critical to ensure timely recognition and care for AAN.

• Anorexia nervosa is a life-threatening disease characterized by pronounced weight loss and substantial multisystem medical risk. • Anorexia nervosa is a life-threatening disease characterized by pronounced weight loss and substantial multisystem medical risk. • Atypical AN can show medical instability comparable to AN; weight loss percentage and rate predict risk beyond body mass index.

• Our study highlights the cross-cultural similarity of AN and AAN. Although AN presents more profound multisystem issues, AAN is comparable to AN regarding vital signs, laboratory measurements, hospitalization, and endocrine dysfunction.