Expert Q&A: A Clinician’s Experience With Hereditary Angioedema

Written by Stephanie Booth
Medically Reviewed by Brunilda Nazario, MD on January 15, 2026
6 min read

Marc A. Riedl, MD, is the clinical director of UC San Diego Health’s U.S. HAEA Angioedema Center. A board-certified immunologist, he is also a member of the U.S. Hereditary Angioedema Association's Medical Advisory Board and a professor of medicine at UC San Diego School of Medicine. 

Hereditary angioedema (HAE) is a rare disorder that causes areas of your body, like your hands, feet, face, gastrointestinal tract, or airway, to swell. Different factors, from stress to hormone changes, can trigger an HAE attack. If left untreated, it can last for several days. In some cases, symptoms can be life-threatening.

HAE usually begins in childhood. But because this condition is so rare, affecting only 1 in 10,000 to 1 in 50,000 people, it may take up to 10 years to get a diagnosis.

We asked Marc A Riedl, MD, the clinical director of UC San Diego Health’s U.S. HAEA Angioedema Center,  to explain more about this rare condition, including why it happens and the importance of early testing and treatment.

Hereditary angioedema is a genetic condition. It's often passed down from an affected parent to a child. However, about 25% of individuals are the first people in their family to have it.

People with hereditary angioedema are missing a protein called C1 esterase inhibitor that basically controls swelling in the tissues. During an angioedema attack, children or adults can end up at the hospital or the emergency department because their face will suddenly swell up, or they'll have trouble breathing. Intestinal swelling can lead to really severe and protracted abdominal pain sometimes leading to surgery. 

These recurrent episodes of skin, intestinal, or airway swelling are very painful. And they can be life-threatening if they hit the airway. 

Some specific triggers can cause attacks, but a lot of people can't predict when or where the swelling will occur. It’s a very anxiety-provoking condition for patients and families.

Blood tests can measure C1 inhibitor protein level and function. There are a few different types of HAE, and most of them will be identified in [these] tests.

 

Most triggers are things we can't control very well — for instance, infections. Physical stress or trauma can also be a trigger. For instance, if someone with HAE bumps their arm or catches their hand in a door. 

For teenagers moving into adulthood, estrogen is a trigger for hereditary angioedema. Females often have more frequent and severe symptoms than males with this condition, particularly as they move into adolescence and adulthood. 

We don't have a cure since it's genetic. It's with people throughout their lifetime, but it can fluctuate in terms of the symptoms. Some people will go stretches of months or years where they don't have many symptoms, but many people do have frequent symptoms for long periods of time. 

We do, however, have good treatment options [today].

Allergy medicines have no benefit for people with HAE. This is a common error that's made. We have to prescribe very specific medicines that have been shown to work for hereditary angioedema. 

We have medicines that will stop these attacks when they happen, which we call on-demand or rescue treatment. We want to make sure every person and family has a plan to treat those attacks when the swelling starts.

The other piece of treatment, which increasingly we're using, is preventative treatment. This is medicine that's given on a regular basis to try to reduce how often these attacks might occur and ideally prevent them entirely. 

There's no evidence that changing your diet or taking a certain supplement — lifestyle modifications per se — will change the natural course of this condition. Other than the medications that have been studied, we don't know of an easy or simple way to correct [HAE], at least not yet. 

We try not to limit activities based on things possibly being a trigger. Yes, this can be a difficult and scary condition, but management has improved to the point where the goal is really to live a normal life. You don't have to restrict your activities, and you don't have to constantly worry about serious complications. 

Do we achieve that 100% of the time? No, but most of the time we can, and that's where having treatment options is so important. It wasn't that long ago that we had virtually nothing to offer families. Things have really changed for the better. We can generally keep people out of the hospital, keep them out of the emergency departments, and get kids back to school and sports and social activities.

If a parent has this, there's a 50-50 chance that their child will inherit that gene. And if they do, it's very likely the child will be symptomatic. 

We really encourage families, if there's a parent that knows they have this or knows that this runs in their family, to get their children tested early. We usually recommend testing at 1 year of age or shortly thereafter for the most reliable blood test results. 

Some families are understandably worried and reluctant, but that leads to delayed diagnosis and puts a child at risk for an episode of swelling that can be dangerous. 

We want to make sure that we identify this early on, so we can prevent complications. There's unfortunately a high rate of anxiety and depression associated with HAE, in large part because it is so disabling and scary and unpredictable. We hope, as we're identifying kids younger and we now have treatments to either treat or prevent these attacks, that we can take some of that burden away.

The U.S. Hereditary Angioedema Association has a huge community of families that are affected by HAE. Connecting to that network can be a huge benefit because you realize you're not alone. There are other people that are facing the same issue. You can get ideas that have worked for other families and then go discuss those with your specialist. 

A lot of patients and families [also] benefit from counseling to just talk through their fears, concerns, and challenges — the part of having a condition like this that is not always addressed by a prescription for a medicine. 

We've made huge strides in the last 10 to 15 years with both rescue treatments and preventative treatments. And there’s a pretty robust pipeline of investigational therapies like oral medicines, which would be great for kids, and injected medicines that may last for three to six months per treatment. 

For people with HAE, including children, things are going to continue to get better and better. I want families to be hopeful and optimistic, because I think that's the reality.