[Diagnosis and differential diagnosis of obesity in childhood]

About 2-3% of "essential" obesity in pediatric age is of endocrine or genetic origin (secondary obesity). The clinical picture of these forms is almost always characteristic; however, some patients affected by secondary obesity can present with an incomplete or atypical aspect. The aim of this review is to offer the pediatrician useful indications to correctly diagnose children presenting with obesity. It is advisable to make a careful anamnesis and an accurate medical examination in order to ascertain the causes that may have contributed to the onset and increase of weight gain. Obesity associated with mental retardation, short stature, cryptorchidism or hypogonadism, dysmorphism with facies sui generis, ocular or uditive defects, might suggest a genetic origin. Prader-Willi syndrome is the most frequent of these disorders and it is due to an alteration of chromosome 15 of paternal origin. These patients have to undergo the methilation test (easy and low cost genetic research) in order to confirm the clinical suspicion. Endocrine alterations, that play a pathogenic role in pediatric obesity (i.e., hypothyroidism, hypothalamic-pituitary diseases, pseudohypoparathyroidism), are rare. Early treatment of hormonal dysfunction generally allows to ameliorate or normalize the weight gain. In absence of specific clinical manifestations or lacking a significant clinical history, no endocrine test is required. The family pediatrician should require some routine hematochimic tests, in order to evaluate the possible presence of hyperlipidemia and/or glycometabolic complications. An oral glucose tolerance test is necessary only for patients presenting with serious weight gain, acanthosis nigricans, and for those with a family history of diabetes. In the most serious cases, a careful cardiovascular and respiratory evaluation should be performed. Children with a suspicion of secondary obesity have to be submitted to an endocrinologist, for a correct diagnosis and a specific treatment. However, the family pediatrician's assistance is essential during the follow-up period, in order to assure the patient and his/her family a proper assistance.