Diego Emilio Lozada, a 23-month-old Mexican boy, attends an annual meeting organized by Fundacion Mar?a Jose, the Prader-Willi association of Mexico, in Mexico City, Mexico on April 9, 2017. Diego weighs 13.5 kilograms (29.7 pounds) and stands 89 centimeters tall (2 feet 11 inches). He has been taking growth hormones since being diagnosed with Prader-Willi syndrome at nine months old. He eats five meals a day and follows a strict sugar- and wheat-free diet. 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 Benedicte Desrus/Sipa USA)