Early warning signs of a pulmonary embolism as Catherine O'Hara's cause of death is revealed

Catherine O'Hara died as a result of pulmonary embolism, a blockage in the lung artery, her death certificate has revealed.

Last month, the Home Alone star died aged 71 last month, sending shockwaves across Hollywood, with her Schitt's Creek co-stars and on-screen son, Macaulay Culkin, all paying tribute to her.

Her management told Variety that the Beetlejuice actor passed away following a 'brief illness', with it later being reported that she'd died in a Los Angeles hospital. The actor is survived by her husband of over 30 years, production designer Bo Welch, and their two sons, Matthew and Luke.

According to the BBC, as well as pulmonary embolism, O'Hara's death certificate also listed rectal cancer as a long-term cause of death.

The death certificate stated the actor had been receiving treatment for the cancer since March 2025, and that they'd last seen her on January 27.

Catherine O'Hara died last month (Frazer Harrison/Getty Images)

What is pulmonary embolism?

To put it simply, pulmonary embolism is a blood clot that blocks the flow of blood to an artery in the lung.

"In most cases, the blood clot starts in a deep vein in the leg and travels to the lung," Mayo Clinic explains. "Rarely, the clot forms in a vein in another part of the body."

Pulmonary embolism can be a life-threatening condition if it's not treated quickly.

What are some of the early warning signs of pulmonary embolism?

Mayo Clinic has explained that symptoms of pulmonary embolism can depend on how much of your lung has been compromised, though there are some common side effects to look out for.

Shortness of breath will typically appear 'suddenly', while having chest pain to the point where you feel you are having a heart attack is another common symptom.

There's also the possibility of fainting episodes with pulmonary embolism, Mayo Clinic went on to explain.

There are many symptoms to look out for (Getty Stock Photo)

What are the other symptoms of pulmonary embolism?

According to Mayo Clinic, other symptoms to be mindful of are:

• A cough that may include bloody or blood-streaked mucus
• Rapid or irregular heartbeat
• Lightheadedness or dizziness
• Excessive sweating
• A fever
• Leg pain and/or swelling, which is usually in the back of the lower leg
• Clammy or discoloured skin

Steve Pugliese, M.D., a doctor and expert in the field, explained how signs can appear before a blood clot blocks the lungs.

It may begin with pain and swelling in the legs due to deep vein thrombosis (DVT), a condition in which a clot forms in a deep vein.

"That will typically happen a few days before," Mr Pugliese explained. "So if all of a sudden you develop pain and swelling in the calf … and it’s not like this was something that happened after exercise, you should be thinking about a DVT that could potentially travel to the lungs."

UNILAD has previously contacted the County of Los Angeles Medical Examiner's Office for comment.