Rare disorder that poisons the body
Tim Chan Tin-sung, who is in urgent need of a liver transplant, is one of only two patients in Hong Kong affected by the rare disorder named erythropoietic protoporphyria (EPP).
However, every sufferer is affected differently, with various levels of severity. Overexposure to the Sun's ultraviolet rays can lead to extreme swelling, rashes and blisters - often on the hands, arms and face - as poisonous toxins are generated in the body.
These toxins build up in the liver, and in extreme cases can result in liver failure. It can lead to a variety of other health consequences, as well.
The disease usually presents itself in childhood, but it can be inconsistent - with different symptoms among various, and even the same, patients - and comes and goes. So it is subject to misdiagnosis as a common allergy.
In some cases EPP is treated with bone marrow transplants, to counteract the enzyme deficiency that causes it. That can relieve much of the condition. Symptoms can also be controlled by limiting exposure to sunlight with clothes and window shades that block ultraviolet rays.
Worldwide, about one in 75,000 people suffer from a form of the disorder.