The Bronchiolitis is an inflammatory disease that affects only the bronchioles and causing an obstruction of the airways quickly. The bronchioles are the penultimate branch of the bronchi, before the alveoli. They are located at the end of the bronchi and are responsible for distributing the inspired air to reach the alveoli where the exchange of gases (oxygen and carbon dioxide) will take place.

The bronchiolitis obliterans is scarring or fibrosis of a prior inflammation around bronchioles. It can be of unknown origin or be associated with different diseases.

Bronchiolitis is known to be a complication that occurs after inhalation of toxins (nitrous oxide, sulfur dioxide, cleaning products or gases caused by combustion) or after viral infections of the respiratory tract (adenovirus, respiratory syncytial virus ).

One of the most frequent forms of presentation of this health problem is that associated with bone marrow, lung, or lung and heart transplants, which is considered a form of rejection of the transplanted organ. It is also associated with connective tissue diseases, especially rheumatoid arthritis .

Its treatment is usually not entirely effective in curing it, leading to chronic respiratory failure in many cases and mortality rates close to 50% in cases associated with transplant patients.

Causes of bronchiolitis obliterans

Multiple factors associated with the appearance of bronchiolitis obliterans are known , although in a small percentage of cases it will remain without a clear cause, then being called cryptogenetics (of unknown origin). Among the factors or causes that cause this disease include:

• Inhaled agents : in this section, derivatives of nitrogen oxide, ammonia, mineral powders, fumes from welding, etc. stand out.
• Infectious agents : there are many related organisms, but are most commonly associated with respiratory syncytial virus, adenovirus and rhinovirus, influenza virus , varicella virus , mycoplasma, nocardia and Bordetella pertussis .
• Pharmacological agents : treatments with busulfan, gold salts, penicillin, rituximab or sulfasalazine, among others, can cause this process.
• Diseases : it is important to highlight the relationship between bronchiolitis obliterans and lung and bone marrow transplantation , as it can be considered a form of rejection or graft-versus-host disease. Also, there is a direct relationship with rheumatoid arthritis , lupus, and dermatomyositis. Also bronchiolitis obliterans can mean a paraneoplastic manifestation (as a consequence of a tumor) when it appears in individuals with pemphigus.

Symptoms of bronchiolitis obliterans

The most frequent symptoms of bronchiolitis obliterans are non-productive cough (dry cough, without mucus) and dyspnea on exertion (difficulty breathing). In cases due to inhalation of toxins or viral infections there is fever and chest pain. Asthenia or noticeable tiredness may also appear, as well as unexplained weight loss for other reasons. The symptoms of bronchiolitis usually appear gradually, evolving in intensity over weeks and even months.

In patients with rheumatoid arthritis and bronchiolitis obliterans, symptoms may appear even years after inflammatory joint symptoms have started, although in a small percentage of cases they may precede or appear at the same time.

The physical examination can be normal or present the typical characteristics of a bronchial obstruction, so when auscultating the patient there is an elongated expiration, snoring and wheezing (lung sounds heard when taking or expelling air). The individual usually presents tachypnea, that is, a respiratory rate higher than the 16-18 breaths per minute that are considered normal.

Occasionally, especially in severe cases with a significant oxygen deficiency, patients appear with cyanosis, which is a purple discoloration of the lips and nails.

Diagnosis of bronchiolitis obliterans

On chest radiography, the most characteristic finding is pulmonary insufflation. If a high-resolution CAT scan is performed , signs of inflammation of the bronchioles, as well as air trapping in them, and a very characteristic mosaic pattern can be seen.

Examination of respiratory function using spirometry shows an obstructive ventilatory disturbance (the air does not penetrate the lungs well) that does not disappear after the administration of a bronchodilator (a drug used to dilate the airways and allow the passage of air) . This fact sets it apart from other diseases whose symptoms could be similar, such as COPD or asthma . In the CO diffusion test we will find a decrease in its values, especially as the disease progresses.

In bronchoalveolar lavage  performed by bronchoscopy , a significant increase in the defense cells in the lung (neutrophilia) is observed. This test is not very conclusive for the diagnosis, but it allows other pathologies to be ruled out. In some cases, such as transplant patients, the definitive diagnosis of bronchiolitis obliterans  must be made by lung biopsy, which could be carried out through the bronchoscopy itself.

Diagnosis of bronchiolitis obliterans

To establish an adequate diagnosis of bronchiolitis obliterans, a lung biopsy should be performed. However, it is normal for the diagnosis to be determined in the presence of certain factors such as:

• If there are antecedents that have been able to influence the development of the disease, such as a transplant, inhalation of toxic substances.
• If the clinical form of establishment has been rapid.
• When the patient suffers from a respiratory obstruction that cannot be attributed to other pathologies and does not respond to treatment with bronchodilators.
• If neutrophilia appears in the bronchoalveolar lavage.

Differential diagnosis should be made with other diseases that present with airway obstruction.

Treatment of bronchiolitis obliterans

The treatment of bronchiolitis consists of reducing the inflammation of the bronchioles through the administration of glucocorticoids,  being somewhat more effective in cases associated with autoimmune pathologies or transplantation. The dose and administration guidelines must be prescribed by a doctor, and it usually takes weeks or even months for the patient to recover. The decision of when to start this treatment is based on the severity and intensity of the symptoms.

When the causes that have triggered bronchiolitis are known, treatment will focus on fighting these factors. The administration of bronchodilators may be beneficial for some patients, as well as antitussive drugs (dextromethorphan, codeine).

When respiratory failure appears, it will be necessary to supply oxygen at home.

In recent years, antibiotics such as erythromycin, clarithromycin, and azithromycin have been used with appreciable efficacy in relieving the symptoms of bronchiolitis obliterans, especially in cases not associated with rheumatoid arthritis or transplanted patients.

Unfortunately, in most cases the treatment of bronchiolitis is not enough to slow the progression of the disease, and although it is variable in each individual, chronic respiratory failure develops with a need for permanent oxygen, a deterioration in the quality of life, and mortality close to 50% of cases in transplant patients.