ESPE Abstracts

Childhood obesity is the consequence of a complex interaction among several factors: environment, genetics, endocrine disorders, medications and other conditions. Genetic factors are described to be causal factors in up to 30–50% of overweight conditions. Although polygenetic obesity is by far the most commonly observed, several obesity related syndromes associated with single gene defects have been identified.

Case presentation: A three year old girl referred to our Clinic with slightly increased TSH value (TSH 5.81 μIU/ml, normal fT₄) and excessive weight gain since she was 2. No anamnestic pathological features were referred. Family history included obesity, rheumatoid arthritis, high blood pressure, a maternal spontaneous abortion at 15w and T2MD. Our first clinical evaluation (at 38 months old) revealed an important weight excess (BMI 25.6 kg/m², SDS 3.78), flat feet, knock knees, pre-pubertal stages, no cognitive impairment or dysmorphic features. Blood biochemical examinations showed normal blood cells count, normal liver and kidneys function, high insulin resistance (G/I 4.64, HOMA index 3.75), normal thyroid function (slightly increased TSH (7.09 μIU/ml), normal fT₄ (14 pg/ml)), prepubertal hormone levels, normal adrenal secretion. Further investigations revealed a normal female karyotype, no organic anomalies (negative brain MR, liver steatosis at abdomen ultrasound), prepubertal features at pelvic ultrasound examination and advanced bone age at X-rays. Once excluded main secondary obesity conditions, a dietetic program was started and the little child was evaluated every 6 months at our center. Although a good compliance to dietary plan and physical activity program, patient’s weight continued to increase (BMI 26.6 kg/m² at 7 months of follow up, BMI 34.1 kg/m² at 39 months). For this reason, CGH-array were performed and revealed a heterozygous deletion of 232 kb (arr[hg19] 16p11.2(28,819,028–29,051,191)×1 in the 11.2 region of chromosome 16 p arm.

Discussion: Loss or gain of material from 16p11.2 is increasingly recognized as one of the most common structural chromosome disorders. The deletion identified in our little patient concerns 12 genes and the most important possible causative gene of her obesity is related to SH2B1 gene. This gene protein is SH2 adaptor protein 1 (SH2B1), involved in leptin and insulin signaling. In literature the loss of this protein has been found associated to a serious early onset obesity with insulin resistance, these features were observed in our patient.

Conclusion: In essential-like obesity not responding to dietary treatment, CGH array could be useful for improve diagnosis.