An annual meeting organized by Fundación María José, the Prader-Willi association of Mexico, in Mexico City, Mexico on April 9, 2017. Prader-Willi Syndrome (PWS) is a rare genetic disorder caused by an abnormality in chromosome 15. In newborns symptoms include weak muscle tone (hypotonia), poor appetite and slow development. In childhood the person experiences a sensation of constant hunger no matter how much he/she eats which often leads to obesity and Type 2 diabetes. There may also be mild to moderate intellectual impairment and behavioral problems. Physical characteristics include a narrow forehead, small hands and feet, short in stature, and light skin color. Prader-Willi syndrome has no known cure. However, with early diagnosis and treatment such as growth hormone therapy, the condition may improve. Strict food supervision is typically required. PWS affects an estimated 1 in 10,000 to 30,000 people worldwide. (Photo by Bénédicte Desrus)