Pneumonitis Vs. Pneumonia

Introduction

The clinical terms ‘pneumonitis’ and ‘pneumonia’ are often confused with each other. Not only do they sound similar, but they also share very similar clinical characteristics. This article sets out to differentiate both disorders and provide a clear overview of what they are, their symptoms, diagnosis, treatment and prevention. 

Both medical terms have the prefix ‘pneuma’. The prefix term pneuma is derived from the Greek term ‘pneuma’, meaning air or breath. This physiologically relates to the respiratory system, which is responsible for gas exchange in the body (oxygen and carbon dioxide). So in the case of pneumonitis and pneumonia, both conditions are disorders of the lungs. 

Respiratory system 

Before we move on to explaining both conditions, it would be helpful to provide a background behind the respiratory system, to fully understand what is happening in both ‘pneumonitis’ and ‘pneumonia’. 

As shown in the image below, the respiratory system is made up of the:

• Nose
• Mouth
• Throat
• Windpipe (trachea)
• Lungs
• Diaphragm 

When we inhale, we are taking in air, in the form of oxygen. We can either take in air through the nose or the mouth. The air then passes through the throat and windpipe, whereby it eventually passes through to the lungs. Within the lungs are these tiny air-filled structures known as alveoli. Air can enter the alveoli, whereby it can diffuse into the bloodstream. Waste products, such as carbon dioxide, are then excreted in a reverse manner - they diffuse from a blood vessel into the alveoli, whereby they are then transported via the windpipes, throat and out the mouth or nose. 

Figure 1: Labelled diagram of the respiratory system. (Image taken from Wikimedia Commons).

Pneumonitis

Definition and characteristics

Pneumonitis refers to the inflammation of lung tissue. This can be caused by, but not limited to, chemicals, allergens, medications or infection.¹

Symptoms

The inflammation of the lungs affects the function of the alveoli. The alveoli play a critical role in enabling the transportation of oxygen into the bloodstream. So when inflammation takes place, the ability of the alveoli to function at full capacity is diminished. Less oxygen enters the alveoli, meaning less oxygen enters the bloodstream and reaches the tissues of the body. Oxygen plays a highly important role in energy production through a process known as respiration. As a result, the following symptoms coincide with pneumonitis:¹ 

• Cough
• Shortness of breath
• Fatigue

Diagnosis

An initial consultation with a GP is first needed, whereby your medical history will be reviewed, symptoms assessed, and a physical examination conducted. Appropriate testing will then be scheduled. This can include the following:¹

• Imaging tests (chest X-ray, CT scan)
• Pulmonary function tests
• Allergy blood test
• Bronchoscopy 

Treatment

Treatment for pneumonitis can include the use of corticosteroids and oxygen therapy. Corticosteroids are drugs that suppress the immune system, which helps to reduce inflammation of the lungs. Oxygen therapy tends to be used if the individual is having trouble breathing. It involves the use of a mask or tube that provides high levels of oxygen.

Prevention

The prevention of pneumonitis is dependent on the underlying cause. Preventive measures such as wearing a face mask to prevent exposure to irritants are often taken. 

Pneumonia

Definition and characteristics

Pneumonia is a subtype of pneumonitis. It is specifically caused by infection of the lungs by pathogens such as bacteria, viruses, and fungi.^2,3

Symptoms

• Fever
• Chest pain
• Productive (wet) cough
• Shortness of breath

Diagnosis

Pneumonia is commonly diagnosed through either chest X-rays or blood tests. Blood tests can include the complete blood count, which is used to identify whether an infection is present based on blood cell numbers. 

Treatment

The most common form of treatment for pneumonia is antibiotics. This tackles the root of the problem which is the infection caused by the bacteria. In some cases, depending on the type of infection, antivirals and antifungals can also be used.

Prevention

There are several ways by which you can reduce the risk of pneumonia. These include maintaining good hygiene (such as washing hands), quitting smoking and incorporating regular exercise into your routine to strengthen your immune system. 

Key differences between pneumonitis and pneumonia

Summary

Both pneumonitis and pneumonia are disorders of the lung. They are characterised by inflammation of the lungs caused by various irritants. Though both conditions are very similar, they do differ with respect to their causes. Pneumonitis can be caused by various factors which include allergens, chemicals, and some medications. Pneumonia is a subtype of pneumonitis and is characterised by inflammation of the lungs caused by infection. As a result, both disorders have slightly different modes of treatment to combat their respective causes - pneumonitis can be treated through the use of corticosteroids and oxygen therapy, whereas pneumonia is treated with antibiotics as it’s caused by infection. There are preventative measures that you can take for pneumonitis and pneumonia, which include good hygiene, regular exercise and the use of face masks if you are in an environment where you are exposed to any of the aforementioned causes. 

FAQs

What are the first warning signs of pneumonia?

The first warning signs of pneumonia typically include symptoms similar to influenza:

• Fever
• Dry cough
• Headache
• Muscle pain
• Weakness

Within 1-2 days these symptoms tend to worsen. 

What are the 4 stages of pneumonia symptoms?

The four stages of pneumonia symptoms include congestion, red hepatisation, grey hepatisation, and resolution. In red hepatisation, red blood cells and immune cells rush to the lungs and alveoli to fight the infection. Grey hepatisation is when red blood cells in the lungs begin to break down, giving off a grey appearance to the lungs. Resolution is the final stage of pneumonia, whereby the body begins to recover. 

How serious is getting pneumonia?

Pneumonia can be very serious, with complications such as respiratory failure, sepsis, and lung abscess arising if left untreated. Identifying symptoms early can help prevent this. 

How long does pneumonia typically last?

Most people with pneumonia get better within 2-4 weeks. 

Is pneumonitis serious?

Pneumonitis can be serious, if left untreated permanent lung damage may occur. However, this can be prevented with appropriate action.