Jose Angel Mendieta, a six-year-old Mexican boy, receives eye drops during an ophthalmology consultation at the Federico Gomez Children's Hospital in Mexico City, Mexico on March 15, 2017. Jose Angel weighs 47 kilos (103.5 pounds) and stands 119 centimeters (3 feet 11 inches). He was diagnosed with Prader-Willi syndrome at age four, a process that took over two years. He lives with his mother. 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)