Situation: A 19-year-old female college student is admitted to a medical–psychiatric unit. For a year she has had eating binges several times a week, followed by self-induced vomiting and, at times, laxative use. Her body mass index (BMI) is 21 kg/m². Which physical finding is typical of repeated self-induced vomiting?

Russell sign, calluses or scars on the backs of the knuckles from contact with the teeth when vomiting is induced, is a classic sign of purging. Other purging signs include dental enamel erosion and parotid gland enlargement. Lanugo and yellow-orange skin are starvation signs seen in anorexia nervosa.

Core concept
This question asks you to differentiate the physical findings of purging from those of starvation. The patient’s BMI of 21 kg/m² is within the normal range, which is consistent with bulimia nervosa rather than the severe weight loss typical of anorexia nervosa. Repeated self-induced vomiting produces localized trauma at the point where the hand contacts the teeth.

Calluses or abrasions over the dorsum of the metacarpophalangeal and interphalangeal joints—known as Russell sign—are the classic hand finding caused by repeated contact of the knuckles against the incisors during finger-induced vomiting. The skin over these joints becomes thickened, cracked, or scarred over time because the same mechanical force is applied several times a week.

Key point! Russell sign is a purging sign, not a starvation sign. It reflects the act of self-induced vomiting itself, not the nutritional deficit.

The other options represent starvation-related or nonspecific findings. Lanugo, or fine downy hair over the back and arms, is a physiologic response to prolonged caloric deprivation and is associated with anorexia nervosa. A yellow-orange tint of the palms and soles reflects carotenemia from excessive intake of carotenoid-rich vegetables in restrictive eating, also more typical of anorexia nervosa. Cracked, reddened skin over both hands is a nonspecific finding that could occur with frequent handwashing, cold exposure, or irritant dermatitis, but it does not have the same diagnostic specificity for purging as Russell sign.

Finding	Mechanism	Clinical association
Russell sign (calluses over knuckle dorsum)	Repeated trauma from teeth against the metacarpophalangeal and interphalangeal joints during finger-induced vomiting	Bulimia nervosa, purging type
Dental enamel erosion	Chronic exposure of tooth surfaces to gastric acid	Bulimia nervosa, purging type
Parotid gland enlargement	Stimulation of salivary glands from repeated vomiting; may be associated with hyperamylasemia	Bulimia nervosa, purging type
Lanugo (fine downy hair)	Thermoregulatory and endocrine response to starvation	Anorexia nervosa, restricting type
Yellow-orange skin tint	Carotenemia from high-carotenoid, low-calorie food intake	Anorexia nervosa, restricting type

Watch out! The presence of Russell sign does not require a low BMI. Because patients with bulimia nervosa often maintain a normal or near-normal weight, the hand finding may be one of the few objective physical clues. This is precisely why orthopedic and dermatologic literature emphasizes that recognizing dorsal hand lesions can aid in early detection of an otherwise hidden eating disorder ^[1][4].

The dermatologic spectrum of bulimia nervosa also includes acne, alopecia, and hypertrichosis, but these are less specific than Russell sign for identifying self-induced vomiting ^[2]. In a study of 200 patients with eating disorders, cutaneous manifestations were common across both anorexia nervosa and bulimia nervosa, but the pattern differed according to the predominant behavior—starvation versus purging ^[3]. When the question describes a normal BMI with bingeing and self-induced vomiting, the physical finding that directly reflects the vomiting behavior is Russell sign.