Interstitial lung disease (ILD) is actually a generic name for a group of very similar diseases that have many symptoms in common, for this reason, a proper diagnosis is necessary in order to receive proper treatment. The common characteristic is that the lungs become inflamed and result in tissue damage. Another name for ILD is diffuse parenchymal lung disease. The way the tissue becomes damaged is that the cells surrounding the alveoli go through a fibrotic process. Alveoli are functional units of the lungs, they are small air sacs through which the exchange of gases, namely oxygen and carbon dioxide, occur. This function is vital to respiration. If they lose their function, we cannot properly take in oxygen and expel carbon dioxide, which is the normal breathing mechanism. If the cells surrounding the alveoli are destroyed by fibrosis, the lungs suffer greatly. The end result is pulmonary inflammation that gives way to respiratory insufficiency, a deadly consequence.
Under normal conditions, alveoli fill up with oxygen during inhalation. During exhalation, the carbon dioxide in our blood goes to our alveoli so that they can be breathed out during exhalation. As mentioned above, the first phase of ILD is that the lung becomes fibrotic either for known or unknown reasons and the interstitium of the alveoli begin to scar, called fibrosis. Due to this altered state of respiration, alveoli become rigid and are unable to expand when the lungs fill up with air. Therefore, the amount of oxygen that we can take in becomes limited, as is our ability to expel carbon dioxide from our body. When this disease is in its advanced stages, breathing turns into quite a difficult task with each passing year.
There are over 310 pathologies that coincide with the concept of ILD, though most of them are very infrequent. The most common are pneumoconiosis, extrinsic allergic alveolitis, sarcoidosis and idiopathic pulmonary fibrosis. Some of these examples can also cause issues in other organs as well. Some studies suggest that just over 49% of ILD cases correspond to idiopathic pulmonary fibrosis and sarcoidosis. However, this is not fully corroborated since a specific diagnosis is not always found.
Interstitial pulmonary diseases can sometimes run their course relatively fast, other times the affectation is more gradual. For this reason, some patients present mild symptoms in the beginning of the disease while others show very severe manifestations. ILD can remain stable, but it can change its severity at any given moment.
The causes of ILD are not known with precise accuracy. It is suspected that one of the factors that precipitates its appearance is the inhalation of toxic materials such as mineral carbon, asbestos, iron dust and silicone.
Some autoimmune diseases can also give rise to ILD. Among them we see rheumatoid arthritis, sarcoidosis and lupus. Medications are a possible cause too and of course, one of the major killers and biggest risk factors is the consumption of tobacco.
Symptoms, Diagnosis and Prognosis
The most glaring symptom is difficulty breathing. At first, the resistance by the lungs to proper breathing is noticed during heavy exercise. It is then presented in daily activities such as eating or speaking. A crackling sound can be heard during auscultation of the thorax. There is also dry coughing, weight loss, fatigue and joint pain. During advanced stages of ILD, the base of the nails become abnormally enlarged. The skin, lips and nails turn purple due to low oxygen saturation in the blood.
Clinical diagnostic tests are ordered by the physician to paint the full picture of the patient’s condition; such tests include radiography of the thorax, CT scan, echocardiogram, pulmonary biopsy, bronchoscopy and arterial blood gasometry.
The prognosis of interstitial lung disease depends on the cause that actually produced the illness and the timing of the diagnosis (early or late stages). However, the most difficult one to treat is idiopathic pulmonary fibrosis.