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The patients from New Zealand, the Netherlands and the UK have hereditary angioedema, a genetic disorder characterised by severe, painful and unpredictable swelling attacks.

However, if they affect the tongue, throat or larynx, angioedema can be life-threatening for the patient due to the potential risk of suffocation.

"Hereditary angioedema can cause patients severe swellings and intense pain, which can be life-threatening as well as restricting normal activities, such as going to work or school," he said.

According to the NHS, angioedema is sudden swelling often caused by an allergic reaction and can be very serious.

There is another kind of angioedema that can occur in the digestive tract.