Two south Wales brothers with the same genetic condition claim the family is victim of a "lottery" for health care.
Harold Morgan says he is disgusted at being refused treatment
William Morgan, of Port Talbot, is having expensive treatment for the genetic condition Fabry's disease.
But his elder brother Harold, diagnosed a few weeks later, has been refused. The family say other relatives in England are also being treated.
Health Commission Wales said some patients were being treated, but the drug used costs £150,000 a year.
Campaigners have said some Welsh patients are losing out, saying the treatment is more widely available in England.
Last year William Morgan, 63, was the first of the two brothers to test for Fabry's disease, which can cause kidney and heart failure and strokes. He then began having enzyme infusions at the Royal Free Hospital in London.
His brother Harold, 70, who also lives in Port Talbot and is a patient at the same GP practice, had suffered health problems for many years and shortly afterwards also tested positive.
But although hospital staff wanted Harold to receive the treatment as well, Health Commission Wales (HCW) refused to pay for it. Now patients from Wales are no longer being referred to the Royal Free for the infusions.
Norris Woodford is concerned about his Welsh relatives
Harold Morgan said he was "disgusted and depressed" that he had been refused.
He added: "They haven't given me a reason why I can't get the same treatment as my brother...It's not a clinical reason, it's a financial one. They are talking about costs all the time."
Because it is a genetic disorder other relatives were tested, and those in England have begun treatment.
They include a cousin, Norris Woodford, of Somerset, who said: "It is obviously a bit of a postcode lottery and I am concerned about my cousins and their young children.
"And quite frankly if I found that my children and my grandchildren could not be treated then I would move across the border into England. I would be an economic refugee, I suppose."
Louise Jones' baby son Carwyn is diagnosed with the disorder
Other relatives are concerned, such as Louise Jones, the Morgan brothers' niece, who was due to return to live in Wales from South Africa next year.
But her three-month-old son Carwyn has been diagnosed with the condition, and the family may reconsider their plans.
Ms Jones said: "I'm extremely concerned because there are children being treated as young as 18 months and it could be very relevant to us very soon."
In England enzyme therapy is centrally funded, and treatment is paid for if patients meet the criteria.
William Morgan has been treated at the Royal Free Hospital
Health Commission Wales told the BBC that it did not comment on individual patients, but it was currently commissioning Fabrazyme treatment for "a number of Welsh patients".
In a statement, the commission said: "Fabrazyme is a high cost drug costing £150,000 per annum per patient."
But HCW said the drug had not been approved by the National Institute for Health and Clinical Excellence (NICE) - the body which decides what medication should be available on the NHS.
It said all new Fabrazyme cases would be assessed by a group set up to advise it on high cost drug therapies.
Christine Lavery of the Fabry's support group acknowledged that Febrazyme was expensive.
But she said: "People in England and Northern Ireland and Scotland and Northern Ireland are getting enzyme replacement for Fabry's disease.
"Whilst we look at the health economics and delivery of that service... we feel that the Welsh are being discriminated against."