What is Interstitial Lung Disease?
Interstitial lung disease (ILD), sometimes also referred to as ‘diffused parenchymal diseases’, is a term that covers a variety of unique lung disorders. These diseases are categorized based on common factors, such as similar characteristics seen in clinical examinations, X-ray images, physical reactions, or disease causes.
Understanding these diseases can be challenging because the terminology is often complex. Essentially, these diseases involve a series of inflammation and severe scarring that affects more than just the “interstitial bed” (the space and tissue around the lung’s air sacs). It alters the “parenchyma” (the parts of the lungs involved in gas exchange, such as the air sacs, air ducts, and small airways).
There’s a very long list of diseases that can cause these lung changes, many of which are extremely uncommon. The way the disease spreads can also vary from one type to another. That’s why it is crucial to get the right diagnosis.
What Causes Interstitial Lung Disease?
Interstitial lung diseases, or ILDs, are a group of conditions that affect the tissue and spaces around the air sacs in your lungs. These diseases are grouped into different categories based on symptoms, what the lung tissue looks like under a microscope, and what it looks like on an X-ray or other imaging test.
Sometimes, ILDs are grouped by what causes them. This could be something that comes from the outside, like dust or chemicals, or something from inside the body. If doctors can’t figure out the cause, then they label the disease as idiopathic or primary, meaning the reason behind it is unknown.
We know that some ILDs are caused by exposure to certain substances in the environment or at work. Stuff like mineral dust (like silica, asbestos, or coal mine dust), organic dust (like mold spores or particles from bird droppings), and harmful gases can damage the lungs over time. It can be hard to know how often this happens. To find out if a patient’s ILD might be linked to something they’ve been exposed to, it helps to look at their full work history and anything they may have encountered at home.
Some ILDs are also linked to autoimmune diseases. In these conditions, the body’s immune system mistakenly attacks healthy tissue. Rheumatology diseases, which involve the body’s connective tissues, can often affect the lungs and lead to ILD.
Taking certain medications can also cause ILD. In fact, researchers have linked over 350 drugs to lung problems. These drugs can either react directly with the lung tissue or trigger a harmful response from the body. To diagnose drug-induced ILD, doctors usually first rule out other causes. X-rays may show a typical pattern, but not always. The look of the lung tissue under a microscope can vary, including patterns compatible with inflammation of the lung tissue due to allergy or hypersensitivity reactions.
The most common type of ILD is the group known as idiopathic interstitial pneumonia. This is a disease that usually involves both inflammation and scarring of lung tissue, instead of infection. There are seven types, which are easily distinguishable by looking at their microscopic features and clinical symptoms. For the majority of these cases, the cause isn’t known, though genetics can sometimes play a role.
Risk Factors and Frequency for Interstitial Lung Disease
It’s been challenging to figure out how often interstitial lung disease (ILD) occurs in the United States, with some suggesting that it may be much more common than previously thought. The low reported count may be due to difficulties in diagnosing ILD, as it’s often identified only after other conditions have been ruled out. However, recent guidelines and classifications have made it easier to recognize the disease. It’s now estimated that there are 30 new cases of ILD per 100,000 people each year. When it comes to the total number of people currently living with the disease, the count is 80.9 per 100,000 men and 67.2 per 100,000 women each year. These numbers come from one of the most significant epidemiologic studies conducted in Bernalillo County, New Mexico.
- Figuring out how often interstitial lung disease happens has been tricky; some believe it’s more common than previously reported.
- The reported count might be low due to difficulties in diagnosing the disease, which is often identified only after ruling out other conditions.
- Recent guidelines have eased the process to recognize the disease.
- It’s estimated that there are 30 new cases per 100,000 people each year.
- The total number of people living with the disease each year is 80.9 per 100,000 men and 67.2 per 100,000 women.
- This data comes from a significant study conducted in Bernalillo County, New Mexico.
Signs and Symptoms of Interstitial Lung Disease
Chronic respiratory conditions often begin with shortness of breath or a persistent cough. Sometimes, patients might not show any symptoms but could still have abnormal lung scans. Additional symptoms can include chest pain, as seen in conditions like sarcoidosis, or coughing up blood, which could signal alveolar bleeding.
Doctors will typically ask about a patient’s environment and work conditions, medications, any exposure to radiation, fumes, dust, or toxins, and their family’s health history. They will also assess for symptoms of rheumatologic diseases. However, shortness of breath could be the only symptom in conditions related to rheumatologic diseases.
During a physical exam, doctors may listen for crackling sounds in the lungs, although these are not always present. In advanced cases, they might notice clubbing or enlargement of the fingers and toes or signs of high blood pressure in the lungs, like an increase in the intensity of the second heart sound.
Testing for Interstitial Lung Disease
Diagnosing the cause and severity of interstitial lung disease, a group of diverse disorders that affect the lung tissues, can be challenging. It often requires a comprehensive approach, including detailed patient history, physical examination, lab testing, imaging, and possibly a lung biopsy. An effective approach often involves collaboration among various healthcare professionals.
To start, the doctor takes a detailed patient history and performs a physical examination. After that, a series of lab tests are carried out. These tests can involve a complete blood count to check for signs of conditions such as hemolytic anemia, seen in diseases like systemic lupus erythematosus (SLE), or eosinophilia, which can indicate a drug-induced disorder. Lab tests can also include checks on liver and kidney functions, along with serologic studies which test for bodily responses to diseases. Depending on the case, tests for infections like HIV or hepatitis may also be conducted.
Imaging is another key part of the diagnostic process. The doctor usually starts with a routine chest X-ray. The most common result is a web-like pattern on the lungs, but other patterns can also be seen. Sometimes, the X-ray can help zero in on potential diagnoses. For instance, swollen lymph nodes in the chest can indicate conditions like lymphoma or sarcoidosis. However, high-resolution computed tomography (HRCT), a type of CT scan that provides more detailed images, can do a better job of characterizing the disease and can sometimes make a diagnosis even when the X-ray result is negative. HRCT can also reveal specific radiological patterns suggestive of diseases like usual interstitial pneumonia (UIP). In cases of UIP, HRCT can show a distinct pattern involving changes at the lung periphery, web-like patterns, ‘honeycomb’ changes, and ‘traction bronchiectasis’ (structural changes caused by diseases).
If the diagnosis remains unclear after analyzing the patient’s medical history, lab results, and radiological findings, more intensive workups may be required. One method is bronchoalveolar lavage (BAL), a procedure where a tube is inserted into the lungs to obtain a fluid sample. The findings from BAL are usually nonspecific, meaning they don’t point to one particular disease. However, BAL can help narrow down the potential diagnoses; for example, increased lymphocytes in the fluid sample can suggest hypersensitivity pneumonitis, a condition caused by inhaled substances. The decision to proceed with a lung biopsy, a procedure where small pieces of lung tissue are removed for examination, should be made on a case-by-case basis. While not all cases require a lung biopsy, it can be particularly useful when diagnosing conditions like sarcoidosis and idiopathic interstitial pneumonia.
Patients with interstitial lung disease should also undergo lung function tests and oxygen level checks. These tests help doctors understand the severity of the disease and monitor its progression.
Treatment Options for Interstitial Lung Disease
For lung disorders where we know the cause, the first step is to avoid whatever is irritating the lungs. General ways to support your health include quitting smoking, going through a program to improve lung function, called pulmonary rehabilitation, and practicing good lung hygiene. Sometimes, extra oxygen is needed if the amount of oxygen in the blood dips below a certain level.
If doing these things properly doesn’t stop the disease from getting worse, corticosteroids, a type of medication, can be used. Corticosteroids can be especially helpful for patients with conditions like bronchiolitis obliterans organizing pneumonia (a disease affects the smallest airways in your lungs) or hypersensitivity pneumonitis (a disease that results from breathing in specific substances from the environment). If corticosteroids aren’t effective, another option is immunosuppressants, which are drugs that calm down your body’s immune system. This is still under investigation.
The main treatment for idiopathic interstitial pneumonia, a type of lung disease whose cause is unknown, is corticosteroids and immunosuppressant therapies. These are used to control the inflammation in the lungs. Recently, two immunosuppressant drugs, nintedanib and pirfenidone, have been approved for use in treating idiopathic pulmonary fibrosis, a specific type of lung scarring. Some research suggests that starting treatment early in the disease might be more effective because the lungs are not yet severely damaged. Once scarring begins, there’s no way to reverse it, but nintedanib can slow it down. If all else fails, a transplant could restore lung function in patients.
What else can Interstitial Lung Disease be?
When diagnosing a lung condition, doctors look at several possibilities that could cause similar symptoms. These include:
- Pulmonary edema (fluid accumulation in the lungs)
- Acute Respiratory Distress Syndrome (ARDS), a severe lung condition causing shortness of breath
- Bacterial pneumonia, an infection in the lungs
- Fungal pneumonia, a lung infection caused by fungi
- Viral pneumonia, a lung infection caused by viruses
What to expect with Interstitial Lung Disease
The likelihood of recovering from interstitial lung diseases (diseases affecting the tissue and space around the air sacs of the lungs) varies according to the different types of this condition. Some types often respond well to treatment. These include acute eosinophilic pneumonia (a rare condition where eosinophils, a type of white blood cell, accumulate in the lungs), cellular interstitial pneumonia (inflammation occurring in the places around the lung’s small airways and air sacs), BOOP (a lung disease with inflammation and scarring), lymphocytic interstitial pneumonitis (a disorder characterized by inflammation and swelling in the lungs), pulmonary capillaritis (inflammation of the small blood vessels in the lungs), granulomatous interstitial pneumonitis (long-term inflammation in the lung), and alveolar proteinosis (a condition where certain proteins build up in the air sacs). The chance of getting better from these diseases also depends on how serious the disease is when it is first diagnosed.
Conversely, some advanced conditions like idiopathic pulmonary fibrosis (a disease where the lungs become scarred for unknown reasons) are especially notorious for not responding well to existing treatments.
Possible Complications When Diagnosed with Interstitial Lung Disease
Complications can include issues such as:
- Worsening lack of oxygen in the blood (hypoxia)
- Heart diseases
- High blood pressure in the lungs (pulmonary hypertension)
- Infections
