Pediatric Examination and Board Review (71 page)

(B) BMI is a direct measure of adiposity

(C) obese children can easily lose weight if they eat properly

(D) obesity occurs when energy intake is balanced by energy expenditure

(E) severe obesity can result from human gene mutations

ANSWERS

1.
(B)
kg/m
²
. Body mass index provides a satisfactory index of adiposity.

2.
(D)
Between 85th and 95th percentile. Cutoff criteria for overweight and obese children are based on the 2000 Centers for Disease Control and Prevention (CDC) BMI for age growth charts. If a child’s BMI falls between the 85th and 95th percentile, he or she is considered to be overweight. If their BMI is higher than the 95th percentile, they are defined as obese. Obesity implies excess body fat. Body fat mass reflects the long-term balance between energy expenditure and energy intake.

3.
(A)
Body builder. The major limitation to BMI is that it does not differentiate between weight that is fat and weight that is muscle. Thus very muscular people may be improperly classified as overweight or obese.

4.
(B)
Weight greater than the 90th percentile of normal. Tall children who are proportional will have weights greater than the 90th percentile of normal and not be obese. However, if a child’s weight is on the height curve, they are likely obese. DEXA scans can demonstrate the distribution and extent of adiposity, but the disadvantage is that sophisticated equipment is necessary. Skinfold thickness is measured with the use of specific calipers. Age- and sex-specific percentiles for triceps and subscapular skinfolds are available, and skinfold thickness more than 85th percentile for age and sex suggests obesity. The disadvantage of using skinfold thickness to classify obesity is that there is significant interobserver error and the measurement becomes less reliable as body fatness increases. Bioelectrical impedance estimates adiposity by measuring resistance to a low-frequency electrical current. The advantage of this method is that it is portable, noninvasive, and reliable in many populations. Disadvantages are that it can be variable, and measurements are compromised with altered hydration and extreme obesity. Measurement of waist circumference is an indirect measure of visceral adiposity. This measurement may help identify those children with an elevated BMI who have the highest metabolic risk.

5.
(C)
Prader-Willi syndrome. A history of feeding difficulty and hypotonia as an infant is found in Prader-Willi syndrome, which is the most common genetic syndrome associated with obesity. Impaired paternal imprinting in the chromosomal region 15q11–13 is found in Prader-Willi syndrome. Laurence-Moon-Bardet-Biedl syndrome, an autosomal recessive disorder characterized by retinal degeneration, mental retardation, obesity, polydactyly, renal dysplasia, and short stature, is a rare cause of pediatric obesity.

6.
(A)
Tall stature. One of the characteristic features of Prader-Willi syndrome is short stature for the genetic background. Patients present with hyperphagia, relatively small hands and feet, developmental delay, almond-shaped eyes, and a characteristic behavioral disorder.

7.
(A)
Normal growth velocity. Children with a hormonal cause of obesity are typically short with a poor growth velocity. Long-standing hypothyroidism would cause short stature, delayed bone age, coarse hair, dry skin, and fatigue. With hypothyroidism secondary to autoimmune thyroiditis, there is often a family history of thyroid dysfunction.

8.
(D)
Cushing syndrome. Short stature associated with obesity should raise the concern of an endocrinologic cause of obesity such as Cushing syndrome or hypothyroidism. Cushing syndrome describes any form of glucocorticoid excess. In children, the first signs of Cushing syndrome are typically growth attenuation and weight gain. The attenuation of growth often occurs before the excessive weight gain. In addition, purple striae are often seen in Cushing syndrome due to stretching of fragile skin.

9.
(E)
Hyperinsulinism. Acanthosis nigricans, or hyperpigmented, thick, velvety areas of skin most commonly on the posterior neck, groin, and axilla, often occurs among obese patients and is a marker of insulin resistance. Although hyperpigmentation occurs in Addison disease, it is most prominent in areas of the skin exposed to the sun and in flexor surfaces such as knees, elbows, and knuckles. In addition, Addison disease presents with anorexia and weight loss, not gain.

10.
(D)
Fasting blood sugar. Obese children are at risk of developing type 2 diabetes mellitus, which usually has an insidious onset. History of frequent vaginal yeast infections should raise the concern of hyperglycemia.

11.
(D)
Type 1 diabetes mellitus. The metabolic syndrome combines atherogenic risk factors with underlying insulin resistance. Key features include hyperinsulinemia, abnormal glucose metabolism (impaired glucose tolerance or type 2 diabetes), hypertension, dyslipidemia, obesity (especially visceral) hyperuricemia, microalbuminuria, and hypercoagulability. With the marked increase in the prevalence of obesity in children, this syndrome will become much more common and eventually lead to increased mortality overall.

12.
(B)
Menstrual history. Obesity in a girl is a feature of polycystic ovary syndrome (PCOS) and is often the presenting complaint. Other features include menstrual irregularity, hirsutism, acne, and insulin resistance.

13.
(C)
Free testosterone. PCOS is the most common cause of hyperandrogenism and typically presents after the onset of puberty. The best way to screen for PCOS is by measuring androgens, including total testosterone, free testosterone, and DHEA sulfate. Measurement of free testosterone is the most sensitive test for the detection of androgen excess.

14.
(C)
Abdomen. Many studies have shown that excess abdominal fat increases the risk of complications independent of and additive to that caused by the degree of obesity.

15.
(E)
More than 70%. Overweight children (age 10-16 years) with at least one overweight parent have more than a 70% likelihood of being overweight as an adult. The persistence of obesity into adulthood is among the most serious consequences of pediatric obesity because there is a tight association between length of time spent at an abnormal body weight as an adult and atherosclerosis, cardiovascular disease, type 2 diabetes mellitus, and dyslipidemia.

16.
(A)
Short stature. Most children with exogenous obesity are tall for age and may appear older than their chronological age. Obese children are more likely to have high fasting insulin levels, and in the past few years, there has been a significant increase in type 2 diabetes. This tends to correlate with the increase in prevalence of obesity in children. Few organ systems are unaffected by excessive adiposity in childhood.

17.
(C)
It has been increasing in all children of age 2-19 years in the past 10 years. The prevalence of childhood obesity has been increasing rapidly in the past 20 years and shows no evidence of slowing. There are significant differences in the prevalence of obesity in various ethnic groups, with non-Hispanic black girls and Mexican American boys having the highest prevalence of obesity.

18.
(E)
Severe obesity can result from human gene mutations. Many factors can result in an imbalance between energy intake and energy expenditure, leading to the promotion of excess fat deposition. Although genes play an important role in the regulation of body weight, behavioral and environmental factors are likely primarily responsible for the dramatic increase in obesity in the past two decades. BMI is an indirect measure of adiposity. A number of human gene mutations have been described that result in severe obesity, including mutations in leptin and melanocortin 4 receptor.

S
UGGESTED
R
EADING

Barlow SE. Expert committee recommendations regarding the prevention, assessment, and treatment of child and adolescent overweight and obesity: summary report.
Pediatrics.
2007;120(suppl 4):S164-192.

O’Rahilly S. Insights into obesity and insulin resistance from the study of extreme human phenotypes.
Eur J Endocrinol.
2002;147:435-441.

Speiser PW, Rudolf MC, Anhalt H, et al. Childhood obesity.
J Clin Endocrinol Metab.
2005;90(3):1871-1887.

CASE 45: A 16-YEAR-OLD BOY WITH FATIGUE, ANOREXIA, INTERMITTENT VOMITING, AND WEIGHT LOSS

A 16-year-old patient presented to the emergency department with the complaints of fatigue, anorexia, intermittent vomiting, and weight loss. He had no diarrhea or fever but did complain of right upper quadrant abdominal pain. He was previously healthy and was not taking any medications. An abdominal computerized tomography (CT) scan was performed that revealed hepatosplenomegaly, and a presumptive diagnosis of mononucleosis was made. He was treated with prednisone for 4 days with marked improvement of his symptoms. His symptoms eventually returned, and following further tests, he was diagnosed with delayed emptying of the gallbladder. He underwent a cholecystectomy 4 months after his initial presentation. He tolerated the surgery well, but on postoperative day 1 he became very sleepy and began to have mental status changes. He improved slightly and was discharged. He now presents back to the emergency department and you find him to be hypotensive with a blood glucose of 50 mg/dL. Further history revealed that he has lost 35 pounds in the last 4 months. On physical examination, he appears dehydrated, and you notice marked hyperpigmentation on the neck, elbows, knuckles, and lower abdomen. In addition, he appears tan even though he has not recently been in the sun.

SELECT THE ONE BEST ANSWER

1.
Which of the following would be the most appropriate initial management of this patient?

(A) IV fluids and stress dose glucocorticoids

(B) oral glucocorticoids

(C) emergency exploratory laparotomy

(D) consult to the pediatric oncology team

(E) insulin drip

2.
Which of the following laboratory results would you expect to find in this patient?