HO CHI MINH CITY, Vietnam (Reuters) - Nguyen Thi Ngoc is dying of old age, yet she is only 13. In the slums of Vietnam`s Ho Chi Minh City, formerly Saigon, Ngoc teaches herself mathematics and chronicles her life and hopes as she waits for a cure to her illness. Ngoc is Vietnam`s first known case of Hutchinson-Gilford Progeria Syndrome, a rare disease that ages the body so rapidly its victims die before they have barely experienced youth. Worldwide only some 100 cases have ever been reported, according to medical journals and doctors. The cause remains as elusive as the cure. But Ngoc has an added disadvantage. She was born in one of the world`s poorest countries, which has neither the means nor the expertise to properly treat her. Doctors at Ho Chi Minh City`s An Binh Hospital have pleaded for international help. Little more than a metre tall and weighing 10 kilograms, Ngoc has the stature of a young child. But in appearance she carries the hallmarks of a woman in her seventies or eighties. She walks with the weary gait of an old woman. Her skin is wrinkled and flabby, her fingers gnarled. But Ngoc makes no willing concessions to old age. Mentally, her doctors have argued, Ngoc is probably more capable than girls her age. But schooling has become another casualty of the disease, not just because of her health but because she has become a novelty. "I want to go to school, but sometimes (students) just laugh at me," she said. Ngoc was born in impoverished central Vietnam, the first child of a farmer who sided with Viet Cong guerrillas fighting against the American-backed army of South Vietnam in a devastating conflict that ended in 1975. Now a noodle-seller on the teeming streets of Ho Chi Minh City, Ngoc`s father makes little more than 20,000 dong ($1.50) a day, most of which goes to rent a tiny room in the seedy slums. "Her condition is getting worse," said Ngoc`s mother. "But we`ll keep doing everything we can for her...so that she can live a normal life like other people." Ngoc has already begun living on borrowed time. The average age when victims of the disease die is 13, but Ngoc is still making plans. "I want to be a doctor," she said resolutely when asked about the future. "To open a private clinic so that I can care for poor and disabled people." Each day she fights on, planning her life with the same precision other girls her age use to put on their makeup. She writes reams of letters to the nurses at the hospital, and when lonely, she writes to herself. The diminutive Ngoc refuses to give up hope.