This conditions is associated with progressive airflow obstruction
(such as that seen with asthma) with scarring in the small airways resulting in
narrowing and their eventual obliteration and destruction.
Conditions Associated with Bronchiolitis Obliterans
Bronchiolitis obliterans have been described in association with a
number of disorders such as:
·
Toxic fume
inhalation
·
Mineral dust
exposure
·
Infection such as
from viruses, and bacteria like mycoplasma and legionella
·
Bone marrow
transplantation
·
Rheumatoid
arthritis
·
Penicillamine - a
medication used to treat certain "autoimmune" disorders
·
Systemic lupus
erythematosus
·
Dermatomyositis
and polymyositis
·
Hypersensitivity
pneumonitis
Patients usually present with a nonproductive cough, progressive
shortness of breath and evidence of airflow obstruction on lung function testing.
Physical examination is usually normal early on in the disease, but may be
associated with wheezing.
Diagnosing Bronchiolitis Obliterans
Routine laboratory studies are usually not helpful. Sputum cultures may reveal causative
viruses, or bacteria in bronchiolitis.
A chest x-ray may show the following:
·
Normal
·
Hyperinflation
(overexpanded lungs on a Chest X-ray)
·
Miliary or
diffuse nodular pattern
Patients with progressive bronchiolitis obliterans often have no known cause
to the Bronchiolitis Obliterans and are frequently classified as “idiopathic”. A lung biopsy should be
considered in those with chronic progressive disease.
Bronchiolitis Obliterans and Connective Tissue Diseases
This is often in association with rheumatoid
arthritis. It affects primarily women
with long-standing, seropositive rheumatoid arthritis in their fifty’s or
sixty’s. The onset and progression of
dyspnea and nonproductive cough can be rapid, as with the rate of progression
of airflow obstruction.
Bronchiolitis obliterans has also been seen in systemic
lupus erythematosus, polymyositis, and dermatomyositis. Penicillamine may also be a cause, but
etiologic cause is lacking.
The chest x-ray usually shows no abnormalities.
Consistent response to corticosteroids has not been shown
and the prognosis is in general poor.
Bronchiolitis Obliterans Associated with Transplantation
This has been described in transplant patients who receive
either donor bone marrow or lung, or heart-lung transplants. The progression of dyspnea and obstructive
airflow is similar as described earlier.
Lung or heart-lung transplant patients usually develop this
2 months or more after transplantation.
Diagnosis
An open lung biopsy is often necessary for a definitive
diagnosis. With these patients it may
be a sign of chronic or repeated rejection, and infection may also play a role.
Bronchiolitis
Obliterans with Organizing Pneumonia (BOOP)
This is a disease whereby plugs of connective tissue extend into the
air sacs obstructing the airway. This
is usually associated with restrictive physiologic changes (like whatis seen in
small lungs) rather than obstructive (such as that seen with BO).
BOOP has been associated with many different conditions such as:
·
Infection
·
Acute Respiratory
Distress Syndrome (ARDS)
·
Bone marrow
transplantation
·
Lung and
heart-lung transplantation
·
Collagen vascular
disease (such as Lupus, Rheumatoid Arthritis)
·
Hypersensitivity
pneumonitis
·
Toxic fume
inhalation
·
Aspiration
pneumonia
·
Idiopathic
(without a known cause)
Signs and Symptoms of BOOP
Most patients have a history suggestive of a slowly
resolving viral pneumonia spanning weeks or a few months. The most common symptom is a persistent,
nonproductive cough, with some patients reporting flu-like symptoms with a
fever, sore throat, and fatigue.
Shortness of breath is usually a significant symptom. On physical exam of the lungs, crackles or a
“Velcro” sound may be present and wheezes rarely are present.
Testing
Chest
x-rays may show
bilateral patchy ground glass, a fine nodular pattern resembling miliary
tuberculosis, bilateral symmetric lower lobe interstitial infiltrates, and on
rare occasions, a normal chest x-ray.
Low
blood oxygen is present
in patients who are symptomatic. Pulmonary function tests show a restrictive pattern, with reduction in the ability
of gases to enter the blood stream from the lungs. Airflow obstruction is uncommon in patients who are not
smokers. It is important to confirm the
diagnosis of BOOP, because most patients will demonstrate complete clinical and
physiologic recovery following therapy with corticosteroids. This usually will require an open lung
biopsy to distinguish BOOP from irreversible interstitial lung disease.
Treatment
Early recognition and therapy of bronchiolitis obliterans
is important, because treatment is often ineffective when the disease has
reached the late, scarred stage.
Inhaled medication to open up airways are usually given for smooth
muscle contraction and symptomatic relief.
Corticosteroids, if given early, may significantly alter the disease
process.
Corticosteroid therapy should be continued for at least 2
to 3 months, then reduced slowly, to minimize the likelihood of relapses with
premature cessation of therapy. In some
patients it may be necessary to continue low-dose or alternate-day
corticosteroid therapy for months or years.
There is a poor response to therapy for Bronchiolitis
obliterans following bone marrow transplantation. By the time severe airflow obstruction has been diagnosed, there
is minimal if any therapeutic response.
Bronchodilators and corticosteroids have not improved airflow in most
cases, and the use of immunosuppressive drugs occasionally is effective, but
has not consistently changed bronchiolitis obliterans.
Adding immunosuppression with high-dose corticosteroids are
used to treat bronchiolitis obliterans after lung or heart-lung transplantation. If this is detected early and therapy is
initiated immediately, the chances of reversal are improved. If therapy is begun late it may stabilize
the process or have no effect.
Corticosteroid therapy in BOOP is effective in most cases, and is often dramatic within 1 to 2 days of
starting therapy. There is an
approximately 65% complete and physiologic recovery in patients.
Since this lesion is so steroid-responsive, it is important
that the diagnosis is established early so that therapy can be started before
irreversible changes in lung function begin.