Anguish of Hong Kong father with rare blood disease who can only be treated by drugs costing HK$4 million a year

Steve Chan always sits quietly in the park while his two young sons enjoy the outdoors, as he never knows when a sudden attack of pain and fatigue from his rare blood disease will strike.

He will continue to be the silent father for his seven-year-old and three-year-old boys until he has access to the world's only medication available to treat his illness, which, at a cost of up to HK$4 million a year, is one of the world's most expensive drugs.

Chan, 39, suffers from paroxysmal nocturnal haemoglobinuria (PNH), diagnosed annually in around one in every one million people. The disease, caused by genetic mutation, leads to daily haemolysis - the destruction of red blood cells - and the release of haemoglobin, a red protein for transporting oxygen, into urine. The condition is particularly active at night. "My urine looks like cola," he said.

Haemolysis causes unexpected abdominal pain, fever or fatigue, and hinders ordinary activities. He lamented that he has only gone on an autumn school outing with his elder son once.

Formerly a Chinese language instructor at a tertiary-level institution, Chan can no longer handle classes that run three hours long. He now works four hours a day as a consultant at his friend's company to allow him greater flexibility and rest.

Since being diagnosed at 14, Chan has relied on blood transfusions and steroids to maintain his health. Now, as his condition worsens, he needs to receive two bags of blood every month to maintain a normal quality of blood. He also has to take five to eight pills of steroids daily, depending on his condition.