By Jane Elliott
BBC News health reporter
Mention the rare enzyme deficiency condition porphyria and the chances are that many people will have never heard of it.
Diagnosis is often delayed
Certainly, most general doctors have never treated a case.
Those who have heard of it are likely to know only that is the condition which is thought to have affected "mad" King George III.
And although that connection has been helpful in drawing attention to porphyria as a condition, it has also helped create a misconception that everyone with it is "mad".
In reality, chronic psychiatric illness is not a feature of porphyria.
Liz Critchley, a 28-year-old student from Bradford, West Yorkshire, was diagnosed with porphyria at the age of 19 and says she meets with a lot of blank faces.
"When you mention porphyria to the general public they may say 'oh that is the condition that King George III had', which can paint it in a distorted light because they believe you must have similar symptoms and must also be 'mad'," she said.
"Or they ask me about the other myth that people with porphyria are thought to be vampires and drink blood.
"When I come across a doctor in accident and emergency I usually have to describe the condition to them. I always carry information on it with me."
She hopes National Porphyria awareness day on Wednesday, will help change this.
The porphyrias, of which there are at least seven different types, are relatively rare disorders.
They are caused by an enzyme deficiency which means the body is unable to properly make the red blood pigment, haem.
Instead the process gets stalled, leading to the accumulation of chemicals called porphyrins.
Precisely which of these chemicals builds up depends upon the type of porphyria.
Symptoms vary according to type and severity, but some include severe pain, sickness, paralysis, sensitivity to sunlight, neurological changes, convulsions, high blood pressure, dark or purple coloured urine and muscle weakness.
There are seven different types of porphyria
These vary in rarity from the most common type (affecting the skin only), which is thought to affect 1 in 25,000 to the acute, which is thought to affect just 1 in 100,000
The ratio of people with the condition is thought to be 1:5 men to women
Almost 90% are women of child bearing age
Liz suffers from acute intermittent porphyria and finds attacks, which can leave her partially paralysed, are at their worst around her periods.
She has gone almost eight months without needing to be admitted to hospital and says her doctors are getting more skilled in keeping her incurable condition in check with weekly infusions of the drug haemarginate, which stops porphyrins building up.
"It is a lot better and more under control. My doctors are learning about it, but it has been a steep learning curve for myself and the doctors."
She said that when she first became ill nobody seemed to realise what was the matter with her.
"It was diagnosed when I was 19. They took a long time to diagnose it and thought at first I was a hypochondriac or that I had an obsessive compulsive disorder with washing because I used to get in to the bath a lot to ease the pain.
"I fell pregnant and I deteriorated even more. They said it was alright and that it was just morning sickness, but I was getting worse and paralysis was setting in.
"Luckily my mum had a friend who was a district nurse and she got a doctor to come and see me and he agreed that there was something wrong.
"It was investigated and it turned out to be porphyria. I had urine like red wine and they were just saying it was blood in the urine."
Because she was so ill Liz had to terminate the pregnancy at 11 weeks, but says signs are hopeful that women with the condition can go on to have successful pregnancies.
Dr Mike Badminton, director of the Cardiff SAS Porphyria Service, based at Cardiff University Medical School, said an early accurate diagnosis was vital.
Not only could the person with the condition be treated better, but also their families could be screened for the genetic condition.
Dr Badminton said the condition could run through generations without people realising there was a problem.
In Liz's family her father had porphyria, although she was not aware of this until after her own diagnosis.
Her brother and sister also carry the defective gene, although they do not have symptoms.
Dr Badminton said knowing there is a family history could help patients.
"We cannot predict who will develop symptoms and who will not.
"We also try to encourage their families to be identified so we can send them information about how to minimise the risks once they are identified."
Dr Badminton said that because the condition is so rare, GPs were unlikely to come across a case in their working lives.
"If somebody comes with an abdominal pain and they are married and in their 30s you might think is it an ovarian cyst, ectopic pregnancy or appendicitis first."
But he said that the condition is getting a wider understanding and even rated a mention on the medical comedy Scrubs.
"Most people say that is what King George had, although whether he did have it or not is difficult to say, but it is certainly keeping the subject alive."