Bronchiolitis Obliterans Organizing Pneumonia

Bronchiolitis obliterans organizing pneumonia (BOOP), also called cryptogenic organizing pneumonia (COP), is a rare disease that causes inflammation in the little air sacs (alveoli) and small airways (bronchioles) in the lungs. The inflammation causes tissue plugs to develop in the airways.

Last Modified: September 5, 2023
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People of all ages can get BOOP, but it typically affects people between 40 to 60 years old. Though the word “pneumonia” is a part of the term, it’s not an infection.

Drugs and health conditions can cause BOOP. Some studies reported a couple e-cigarette users with BOOP, but most cases have no known cause. When BOOP has no known cause, medical providers may call it idiopathic BOOP or cryptogenic organizing pneumonia (COP). “Cryptogenic” refers to the disease’s unknown cause.

While the medical community prefers the term “COP,” the term “BOOP” is recognized and used throughout the world.

BOOP accounts for about 20 to 30 percent of chronic infiltrative lung disease cases in the world, according to BMJ Best Practice. In the United States, it accounts for about 5 to 10 percent, according to the National Organization for Rare Disorders.

People with BOOP may not have any symptoms, but others suffer acute respiratory distress.

If it’s diagnosed early and treated quickly, the disease responds well to therapy. But some people may have lung problems for the rest of their lives.

Shortness of Breath and Other Symptoms

Symptoms of BOOP vary with individuals, and some people may not have symptoms. Symptoms develop over a few weeks or months. People with a rapidly progressive type may have respiratory failure within a few days, and this type is linked to lung scarring.

The first symptoms in more than two thirds of people are shortness of breath and dry cough, according to Gregory A. Schmidt and Gary W. Hunninghake. Wheezing and coughing up blood are rare.

In addition to respiratory distress, people with BOOP suffer from a general feeling of being unwell and flu-like symptoms. If left untreated, symptoms may become progressively worse.

BOOP symptoms include:
  • Chest pain (rare)
  • Chills and shaking
  • Coughing up blood (rare)
  • Crackling or rattling sounds in the lungs
  • Dry cough lasting for 2 to 4 months
  • Fatigue
  • Fever
  • Flu-like symptoms
  • Joint pain (rare)
  • Loss of appetite
  • Night sweats (rare)
  • Shortness of breath with exertion
  • Weight loss

Cause & Diagnosis

Researchers don’t know what causes most cases of BOOP, but there are several possible causes. For example, patients of solid-organ transplants are especially vulnerable to BOOP, according to a February 2022 case report in Pediatrics.

Smoking isn’t typically a cause of BOOP, but recently some researchers have reported a couple of cases of BOOP linked to e-cigarette use.

Potential causes of BOOP include:
  • Certain viral respiratory infections
  • Cocaine
  • Connective tissue disorders
  • Exposure to chemicals
  • HIV infection
  • Inflammatory bowel disease
  • Inhaling toxic gases
  • Medications
  • Organ transplant side effect
  • Radiation therapy


In order to diagnose BOOP, doctors will perform a clinical evaluation, look over patient history and perform imaging tests on the lungs and a lung function test to rule out other diseases.

Radiographic studies for BOOP include X-rays and high-resolution computed tomography (HRCT) of the chest. Most often, lung biopsies are effective at diagnosing the disease.

E-Cigarettes and BOOP

Side effects of e-cigarettes include e-cigarette or vaping product-use associated lung injury (EVALI), coughing and sore throat. Though there is no clear link between e-cigarettes and BOOP, there have been at least three case reports of e-cigarette users diagnosed with BOOP.

Forty-Year-Old Female

In a 2018 case report, published by Dr. Mohammad Saud Khan and colleagues in The Clinical Respiratory Journal, researchers wrote about a 40-year-old female who had used e-cigarettes to quit smoking. She had shortness of breath and chest pain that lasted for about a month and developed respiratory failure that required intubation with a ventilator.

They diagnosed her with organizing pneumonia after performing a biopsy. They noted it was the second case of organizing pneumonia related to e-cigarettes. Doctors successfully treated her with steroids.

Twenty-Seven-Year-Old Male

In a 2020 case report, Ronnie D. Mantilla and other researchers in the American Journal of Respiratory and Critical Care Medicine wrote about a 27-year-old male e-cigarette user who had shortness of breath, fever and cough. He developed respiratory failure that required intubation with a ventilator.

A lung biopsy revealed he had BOOP. After treating him with high-dose corticosteroids, he recovered and left the hospital after two weeks.


BOOP is a highly curable disease. In some cases, mild BOOP may go away on its own. Doctors may monitor people with mild cases and may treat them later.

A common treatment for BOOP is a regimen of corticosteroids, and it responds well to this type of therapy. Most people recover after a few weeks or months of treatment. But in some people, BOOP can get worse even after treatment.

The most popular drug treatment is prednisone. In fact, idiopathic BOOP can be cured in about 65 to 80 percent of patients with prednisone therapy, according to Dr. Gary R. Epler. Symptoms begin to improve within days or weeks.

BOOP can recur in some cases, but it responds to an additional course of treatment. In cases of rapidly progressive disease, the chemotherapy drug Cytoxan and intravenous corticosteroids have been effective.

Some people who do not respond to corticosteroids have had to use investigational medications such as cyclophosphamide, azithromycin, and mycophenolate mofetil. In rare cases, doctors may recommend a lung transplant.

Please seek the advice of a medical professional before making health care decisions.