The primary immunodeficiencies are a group of incurable conditions that affect the body's immune system. A person who has one of these conditions has little or no natural defence against infections. He or she can experience a variety of problems, ranging from recurrent colds and other respiratory ailments to heart problems, pneumonia, skin disorders and arthritis.

The comparative rarity of these conditions means that some people remain undiagnosed for many years, resulting in organ damage and even disability.

"I wasn't diagnosed until I was about 50. The doctors realised that I had probably had this condition since the age of about six months - and possibly from birth." (Adult with CVID)