[Something new in the genetics of monogenic obesity and its insights into pathophysiology].

Obesity is a complex, multifactorial disorder. About 5% of obese patients actually present with a monogenic form of obesity where only one mutation is sufficient to cause the disease. So far, the genes that have been found to be mutated in these monogenic forms play a key role in the leptin/melanocortin pathway which is mainly active in the hypothalamus and which regulates food intake and energy expenditure. Our laboratory has recently reported a novel monogenic form of obesity due to MRAP2 deficiency where, contrary to previously described monogenic forms of obesity, the carriers presented with hyperglycemia and hypertension in addition to obesity, suggesting that MRAP2 might play a pleiotropic role in metabolic tissues, in addition to its role in brain control of food intake and energy expenditure.