Although the symptoms of PNH were known as far back as 1882, in 1995, clinicians still had little idea about what would happen if patients were treated with blood thinners and red blood cell transfusions instead of bone marrow transplants. Peter Hillmen and colleagues wanted to see how people like this fared over time, to establish what they called the ‘natural history’ of PNH.
So, they studied a group of 80 patients who were referred to London’s Hammersmith Hospital between 1940 and 1970 and followed their progress for as long as they could. Most of the patients were in their forties when they were diagnosed, and although a quarter of them lived on for 25 years, the average survival time was just 10 years. Thirty-one developed blood clots, and around half of those for whom the cause of death was known, died either from a clot or a haemorrhage.
It’s important to stress that this was in a time before modern drugs, such as eculizumab and ravulizumab, were available. With these improved treatments, people living with PNH can now expect a completely normal life expectancy.
In addition, the study found that 12 of the patients had spontaneous remissions. Their PNH disappeared on its own, usually somewhere between 10 and 20 years after their diagnosis. Also unexpected, none of the original 80 patients went on to develop blood cancer, which was thought to be a risk of PNH. This suggested that leukaemia is relatively rare in patients with PNH, which remains the case today.