Interstitial lung syndrome: is it serious?

Definition: what is an interstitial pulmonary syndrome?

“The lung has two very different structures: conduction pathways gathering trachea, bronchi and bronchioles – which are cylindrical structures – and at the end, the lung parenchyma that spreads over a large areaexplains Professor Jacques Cadranel, head of the Department of Pneumology and Thoracic Oncology at the Tenon Hospital, a constituent center for Rare Pulmonary Diseases. The lung parenchyma has a fractal structure; that is to say, a very complex three-dimensional structure which allows it to develop a maximum exchange surface (about the size of a tennis court) in a minimum volume, that of your thorax. Due to its architectural constraints, the lung parenchyma is an extremely fine and fragile structure..” The alveoli are the elementary structures of the lung, they play a role of exchanger between the air and the blood of the pulmonary capillaries. To ensure the framework of the parenchyma and the pulmonary capillaries, there is a supporting tissue that we call the interstitial tissue formed by fibroblasts. It is from this tissue that develop diffuse interstitial lung disease (PID).

When cell-to-cell communication fails in the lungs, it can develop interstitial lung disease.

“The lung is a very special organ, it receives all the body’s blood containing the red blood cells which bring oxygen to the organs and the white blood cells including the immune and inflammatory cells. The role of the lung parenchyma is to diffuse oxygen from the air to the hemoglobin of the red blood cells at the rate of 12 breaths of half a liter of air per minute, i.e. nearly 9000 liters of air per day ! The lung is therefore permanently exposed to microbes, pollutants and organic compounds contained in the air. It must be continuously controlled in terms of immunity so as not to develop a respiratory disease at any time. Due to its complexity, the lung brings together in a restricted space at least thirty different cell types… So when intercellular communication is dysfunctional in the lungs, it may develop PID,” explains Professor Cadranel.

One or two lungs affected?

Diffuse interstitial lung disease is an “inflammation of the lung” which involves the cells of the “interstitial tissue”. They are often diffuse because they affect “both lungs”. “Interstitial lung diseases are the most complicated pathologies for a medical student. They are poorly known to the general public and in general to general practitioners. These pathologies are complicated, even for pulmonologists. It is an over-specialization“, confesses Professor Cadranel.

What are the symptoms of an interstitial syndrome?

Two main symptoms are common to diffuse interstitial lung disease:

• Shortness of breathrelated to the thickening of the alveolar walls and;
• A cough : on auscultation the physician hears crackles.
• Sometimes fever

Interstitial pulmonary syndrome can be very acute and brutal: “one day the patient feels fine, and the next day he arrives at the emergency room“. Symptoms can also be chronic and settle gradually over several monthseven several years.

What causes interstitial syndrome?

Interstitial lung disease is difficult to classify. Nevertheless, “we separate cancers, infections and inflammatory diseases. You should also know that the lungs are the ears of the heart: the heart and the lungs are completely interdependent“says the pulmonologist.

► When IRS is acutewith the presence of fever, a flu or Covid-like infection is often the cause of interstitial lung syndrome.

► In the absence of feverthe origin is often cardiac (heart failure)pathology in which “the heart flooded the lung“.

► One time out of two, no cause for this particular form of pneumopathy is found (Idiopathic PID).

► In the other half of the cases, it concerns several groups of diseases.

• vasculitides are an inflammation of the pulmonary capillaries. A leak of blood takes place at the intra-alveolar level (hemorrhage). As a result, the alveoli fill with blood and can no longer perform their function.
• The tobacco : the lung is loaded with a very large number of inflammatory macrophage cells;
• Environmental Inflammation by exposure to: fungi, moulds; mineral particles among construction workers (silica, asbestos) or fire smoke among firefighters; medications, or prolonged exposure to bird droppings.
• Autoimmune diseases: rheumatoid arthritis, scleroderma, Gougerot-Sjögren’s disease, inflammatory myopathy, lupus erythematosus, etc. ;
• Sarcoidosis (immune system dysfunction): This is one of the most common and well-known causes.

► The genetic heritage is also a risk factor for developing interstitial lung syndrome. “For example, diffuse interstitial lung disease can be caused by diseases of aging (telomeropathies) causing premature aging of the lungs, which heal poorly“, illustrates Professor Jacques Cadranel.

Is it serious or fatal?

Interstitial lung syndrome affects the patient’s breathing capacity. “It’s a serious disease, but which can be treated well when the origin is infectious, if the patient quits smoking or stops the responsible exposure. The main risk is chronic respiratory failure. Sometimes, the use of a lung transplant is necessary“, specifies our interlocutor.

What is the life expectancy with an interstitial syndrome?

The scope of interstitial lung disease is far too vast to give a prognosis. “The most complicated PID to treat is idiopathic pulmonary fibrosis. The most common, caused by sarcoidosis, has a good prognosis. In the case of covid, the interstitial pulmonary syndrome disappears completely in almost 100% of cases. The development of pulmonary fibrosis associated with covid is exceptional, especially with vaccination, thanks to which the Sars-Cov-2 virus no longer descends into the lower respiratory tract“, specifies the expert in rare pneumopathies.

What tests to make the diagnosis?

“During the clinical examination, we distinctly hear cracklesa sound similar to the sound of a footstep in the snow or like Velcro, explains the specialist. The reference examination is the chest X-ray. “On the x-ray, the lung, which is normally black, becomes whiter. The organ condenses and presents lines or micro-nodules. Sometimes, when the alveoli are filled, we observe a blurred opacity at the thoracic level“, details our expert. CT scan reveals thickening the structure of the lungs, nodules or micro-nodules, lines, nodes and opaque alveoli, filled with fluid or inflammatory cells. Other indirect examinations are carried out depending on the pneumopathies, such as a blood test, an alveolar lavage, a cardiac examination or blood gases (measurement of the gas exchange deficit). More rarely, a lung biopsy is prescribed, especially in cases of idiopathic interstitial pulmonary syndrome.

How to cure an interstitial syndrome?

The first measure is avoidance of toxic agents responsible for diffuse interstitial lung disease (tobacco, medication, exposure to animals, birds, etc.). “Then we treat the disease, such as heart failure or lung infection. The purpose of the processing is to reduce inflammation with biotherapy or cortisone and to avoid abnormal scarring of the lung with an anti-fibrosis”concludes the pulmonologist. oxygen therapy is sometimes recommended to improve the breathing capacity of patients. In addition, vaccination against influenza, Covid or pneumococcus is recommended for patients and those around them.

Thanks to Professor Jacques Cadranel, head of the Department of Pneumology and Thoracic Oncology at Tenon Hospital, a constituent center for Rare Pulmonary Diseases.