TANG Xu sat for the grueling three-day College Entrance Examination in his wheelchair, using only his forefinger - his only capable finger - to hold his pen.

He did fairly well and expects to hear this month about majoring in computer science or language at Shanghai Normal University or Shanghai Maritime University.

"No matter which university admits me, I won't regret anything because I've tried my best," says the 18-year-old who lives in Shanghai's Xuhui District.

Tang suffers from duchenne muscular dystrophy (DMD), a progressive, incurable and fatal neuromuscular disease. The cause of most cases is unknown but progression can be slowed. Tang's case is genetic and he was diagnosed at the age of five. DMD is usually fatal in five years.

Tang is one of at least 16.8 million Chinese suffering from one of around 6,000 rare diseases, also called orphan diseases. Eighty percent are genetic, chronic and fatal; only around 1 percent are curable. Very few "orphan" drugs are available because development is prohibitively expensive; they are not profitable.

The world's most famous sufferer of a rare disease is British physicist Stephen Hawking, who has amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

Most rare disease patients in China are unknown and receive little care or attention. Most treatments are unaffordable.

Though China is expanding health care coverage, there's no insurance coverage for rare diseases. There's no official definition, no legislation and generally no social services for sufferers.

The recently established Shanghai Rare Disease Society, consisting of 28 medical professionals, is trying to win local government support for a temporary Shanghai health care insurance program for rare diseases - it would be the first in China. Professionals propose coverage for 12 rare diseases that they consider preventable, treatable or curable.

These include Gaucher's disease and Fabry's disease, both inherited disorders in which the body is unable to metabolize lipids, which build up in cells and organs, causing enlargement, pain and impaired function. Some types are treatable.

There's no generally accepted definition of a rare disease, it may vary by country and population. According to the World Health Organization definition, a rare disease affects 0.065 percent of a population. By that definition, China has at least 16.8 million sufferers, a conservative estimate.

Very few drugs for rare diseases in developed countries are available in China and few are affordable, says Sun Zhaoqi, a representative of the National People's Congress, the country's lawmaker, writing in The Lancet British medical journal in late February.

Diagnosis is difficult since many doctors haven't seen rare diseases.

"I was misdiagnosed in many different hospitals across southern China before DMD was confirmed in Nanjing and then I was told it was incurable," says Tang. "I hope someone will know how to cure me some day."

"The fundamental solution is legislation," says Dr Li Dingguo, vice chairman of Shanghai's lawmaking advisory committee and formerly a senior doctor at Xinhua Hospital. "Legislation takes a long time, so the first step is insurance." Li is head of the Shanghai Rare Disease Society.

Dr Gu Xuefan of Xinhua Hospital, also from the society, says insurance for rare disease patients is a matter of social justice. "They can't choose to be healthy, they can't choose to buy cheaper drugs," Gu says. "Thus, it's not fair to exclude them."

According to Gu, patients with terminal cancers can get maximum insurance of 200,000 yuan (US$30,890). WHO considers Tang's disease to be as fatal as some cancers, but he doesn't fit into any category for Chinese medical insurance.

When Tang was a child, he fell down a lot but before fifth grade he was still able to walk. His progressive weakness is caused by a genetic mutation resulting in muscle deterioration, difficulty breathing and eventually death.

Tang has felt the weakness spreading from his legs and trunk to his arms, neck and head. In 2000 his parents left their rural home in Jiangsu Province and came to Shanghai seeking better medical treatment.

The Shanghai Education Commission helped Tang get a month of free rehabilitation therapy in Huashan Hospital, and he felt better. But his farmer parents couldn't afford continued treatment. Tang went back home and waited.

But he didn't give up. He wrote to several middle school masters, saying, "My will to study is stronger than any student's and I can do well." His words moved the head of Changqiao Middle School in Xuhui District and Tang was accepted. Then he made it to high school in Shanghai.

Tang's parents have been doing whatever they can to support his studies. His father gets up at 2am every day to deliver milk and his mother works as an ayi. Every day at school Tang doesn't drink water so he doesn't have to be helped to the bathroom. He uses one forefinger to support his pen. For several years he has ranked among the top three in his class.

"Most children I met with neuromuscular diseases are very brilliant and persistent," says Zhu Changqing, associate professor at Shanghai Second Polytechnic University who herself is an NMD patient. "They are smiling and coping with their fate every single day."

On her own, Zhu founded the Neuro-Muscular Dystrophy Association of China (MDAChina), a nongovernmental organization that unites patients and calls for research and social support at home and abroad. Tang is a member.

In 2009, China launched reform of its national health care system, with an initial three-year budget of 850 billion yuan. The system has been substantially privatized, but new guidelines emphasize reasonable distribution of resources and core issues of equity and accessibility. But in the middle of 2011, most of the vast undertaking remains to be tackled.

What MDAChina sees is just the tip of an iceberg of silent suffering. Most patients are in rural areas and cannot afford treatment. Fortunately, more people are aware of China's rare diseases. Patients, families, organizations, doctors, foreign orphan drug companies and government officials are working to draft a rare diseases prevention and treatment law.

There are many Chinese organizations for rare diseases. They include China-Dolls Care and Support Association; the Hemophilia Home of China; the Home of Babies of the Moon and China Albinism Association. They address patients' physical and psychosocial needs, raise funds and lobby for better treatment.

In March 2009, the China Charity Federation established an office for rare disease aid. Nine months later, the Rare Diseases Aid Foundation was set up to provide both medical knowledge and social assistance to patients and families.

Officials of the China Charity Federation were unavailable to comment about the Shanghai Rare Disease Society.