The rare disease mistaken for asthma

Dr Luke Howard is a pulmonologist and treats patients with Pulmonary Arterial Hypertension (PAH) – a rare and potentially fatal heart and lung condition that is often misdiagnosed. With symptoms which can appear vague, from breathlessness and fatigue to dizziness, PAH is regularly mistaken for asthma, anxiety or a lack of fitness.

Patients often notice the symptoms of PAH for the first time when they exercise. They might feel dizzy or breathless or even faint. My plea to any GP who sees a patient like this is please refer them to a heart or lung service – especially when the common signs of asthma, like coughing or wheezing, aren’t present.

PAH is hard to diagnose in patients because the symptoms can be vague – blackouts, fatigue, chest pains, swollen ankles – people tend to think it’s the general stresses and strains of life, or even depression, causing them to feel this way.

GPs don’t immediately consider PAH because it’s a rare disease – nor do we expect them to. But left undiagnosed sufferers can lose their independence quickly and become hospitalised. As PAH progresses, it can be fatal.


Pulmonary Arterial Hypertension happens when the small blood vessels in the lungs become narrow making it harder for the right side of the heart to pump blood through the lungs and around the rest of the body. Unlike heart attacks where fatty deposits build up in the arteries, it’s the cells in the lining of the blood vessels in the lungs that reproduce rapidly and cause the vessels to become narrowed or blocked.

PAH is a progressive condition and affects predominantly young to middle-aged people and more women than men. By the time a patient starts to experience symptoms and is referred for treatment, PAH is often quite advanced and the resistance to blood flow in the lungs is already ten times higher than normal. Over time the symptoms that were only present when exercising, start to affect a patient’s ability to complete everyday tasks and activities.

At the onset of the disease a patient’s heart will compensate for the increased blood pressure in the lungs, but eventually it stops being able to pump against the pressure, which can lead to heart failure and sudden death.

Genes and risk factors

Some cases of PAH come out of the blue with no known trigger. Around one in five sufferers has an abnormal gene, but not all have inherited the gene from their parents as the gene defect can develop from scratch in a mother’s egg or father’s sperm. Sometimes the gene is inherited from a parent who does not have PAH, since not everyone with the gene gets it.

You may develop PAH if you suffer from other conditions like congenital heart disease, HIV, liver disease, or connective tissue disease like Lupus or Scleroderma. Generally there is a genetic cause, pre-disposition or other medical condition that increases your chances of developing it, but we don’t know what other factors may trigger it in an individual. An infection in the body or some other sort of injury can act as a catalyst for the cells in the lungs to act abnormally and this can lead to the development of PAH.

The simplest way to detect the condition is with an echocardiogram – a straightforward ultrasound scan of the heart. Alone an echocardiogram isn’t enough to make a formal diagnosis, so other scans and tests are needed. Once a patient has a suspected diagnosis of pulmonary hypertension, they should be referred to a pulmonary hypertension centre as soon as possible so they can start treatment if appropriate.

At Hammersmith Hospital we run a specific clinic where we offer genetic counselling to families when a relative has been diagnosed with PAH. The family may want genetic screening themselves, or prefer to have a yearly echocardiogram to determine if they are developing the condition. The earlier we can detect and treat it the better.

We are one of a few services in the country that offers routine cardiopulmonary exercise testing assessment, where we ask patients to use an exercise bike, measure their heart rate, blood pressure, breathing and oxygen consumption. We have a real interest in seeing this test being used more widely and believe it is a very powerful investigation for patients with undiagnosed breathlessness.

Survival rates

We look after over a thousand patients a year in our pulmonary hypertension service and receive around 300 new referrals annually. Newly diagnosed patients are often really scared by the time they see us, because it can take months to get a diagnosis and they may have been reading about PAH on the internet. I tell them how many of the patients I have been treating for over a decade are living close to normal lives.

On average fifty per cent of patients diagnosed with PAH survive up to nine years with treatment. This means many live much longer, although some are sadly referred to us towards the end of their life with advanced PAH. The key determining factor is early diagnosis and referral to one of the seven specialist centres in the country so patients can begin treatment.

There are different types of PAH so the treatments and therapies we offer vary too. The medication we prescribe dilates the arteries in the lungs and helps them to relax. It has the ability to reverse some of the structural changes in the blood vessels too, like the thickening up of the arteries. Many of the therapies are tablets but some patients use medication which they inhale, or which is infused into a vein through a hidden catheter. In cases where a patient has a chronic blood clot they may need to have a surgical procedure known as a pulmonary endarterectomy; this can result in a complete cure.

Emotional resilience

The earlier patients start treatment the better. While we know treatment can double or even triple patients’ survival rates, the quality of life the patient has depends on the individual. For some patients even mild symptoms when they exercise have a huge impact on their quality of life. To a certain degree it’s about emotional resilience and how well a person copes with their illness. Some patients have an excellent long-term outlook, but feel very unwell because of the psychological impact of their condition.

At Hammersmith Hospital we aim to build trust and offer psychological support to all our patients to help them back to independence and confidence. We are a multi-disciplinary team of four consultants and four nurses. Our nurses are trained in health coaching so they can support patients to build up emotional resilience. PAH sufferers can have a range of symptoms that are not outwardly visible. Psychologically this can be very challenging for patients who look well on the outside but are suffering breathlessness, dizziness, tightness in the chest and swollen ankles, alongside the fear of how rapidly their condition is progressing.

Advice for patients

While there are many causes of breathlessness PAH is one of them. If you have breathlessness lasting for more than a few weeks and you are finding that you can do less than you did before, or that you can do less than your peers, go to your GP and ask to be referred to a pulmonologist or cardiologist. Chest pain, dizziness on exertion, swollen ankles or abdomen and especially blackouts are a warning sign that you need attention.

Advice for GPs

If you have a breathless patient with no clear diagnosis, or a patient who has additional symptoms such as ankle-swelling, chest pain or fainting, you can refer them to our community cardiology and respiratory service. If a patient already has suspected PAH or pulmonary hypertension due to pulmonary emboli then refer directly to us. For questions about PAH email For urgent advice call 020 3313 8072. Other hospital-based teams can also contact us through this route to refer.

Read about patient Kinari Mehta’s moving experience of living with PAH

More than 3,000 people in the UK are being treated for PAH – but many more are undiagnosed. Find out more about PHA