What is EGPA (Eosinophilic Granulomatosis with Polyangiitis)?

EGPA is a type of vasculitis, which is inflammation of the blood vessels caused by the body's immune system attacking blood vessels by mistake. EGPA was formerly known as Churg-Strauss syndrome, after the doctors who first identified the condition at Mount Sinai Hospital in New York City in 1951. To understand the full name of this disorder, let's look at each element of the name, starting at the end.

Polyangiitis is a disease in which the blood vessels have become inflamed, and crucially this inflammation is present in two or more of the different varieties of blood vessel found in the body. For example, the problem could affect both veins and arteries, or, at a smaller level, venules and arterioles. Granulomatosis is the condition whereby the body's immune cells cluster round a foreign body, or something perceived as foreign. Finally, eosinophilic means relating to a type of white blood cells that are made visible when stained with a dye called eosin. It is the preponderance of these cells which marks EPGA out from other types of vasculitis.

EGPA is almost exclusively a disease of adults aged between 30 and 45, and seems to affect men and women equally. In countries with well-developed health systems, approximately 12 people per million are diagnosed with EGPA. The most distinctive symptom of EGPA is severe asthma which develops in adulthood. The asthma may occur before other symptoms appear, making EGPA difficult to diagnose in its early stages. The other most common symptom which characterises EPGA is allergic sinusitis. There are many other symptoms including fever, muscle pain and weakness, tiredness and weight loss. In advanced cases there can be damage to the skin, nerves and major organs such as the kidneys, lungs and heart.

Many of these symptoms occur in other medical conditions, but the definitive test of EGPA is the count of eosinophils in the blood. In a healthy person, the percentage of this type of white cells is 5% or less of the total white blood cell count. In a sufferer of EGPA this figure will be 10% or more, and can rise to 60%.

The cause of EGPA is uncertain, and it is thought that the disease is caused by a combination of multiple factors. Some geneticists believe that they may have identified a genetic component, but it is extremely unusual to see more than one case in a family. Some doctors and researchers think that industrial solvents may play a role, while others think that some kind of infection may trigger the condition. As yet, all these ideas are only theories which are yet to be proved or disproved.

The principal treatment of EGPA is to prescribe a steroid such as prednisolone in tablet form, the aim being to control the vasculitis so that damage to tissues and organs is prevented. A steroid nasal spray is also often given to treat the common symptom of sinusitis. If steroids are seen to be ineffective, anti-cancer drugs such as cyclophosphamide may also be prescribed. In general, the initial treatment of EGPA involves using very high doses of these drugs, which means that patients need to be closely monitored for side effects. Dosage of these drugs will be gradually tapered off over a period of up to two years. Before the development of these drugs, EGPA was almost always fatal. Nowadays, one year after diagnosis 90% of sufferers survive, with 85% still alive after 5 years.