The most common symptoms of lung fibrosis are breathlessness on exertion (exertional dyspnoea) and cough. The body’s exercise capacity decreases usually gradually and is thus often explained by affected individuals as normal limitations due to ageing. A reduction in the limit of performance during sporting activities is the most likely feature. In everyday life, the first problems usually occur when climbing stairs. If the disease progresses, the breathlessness may even occur at rest (dyspnoea at rest). The oxygen deficiency may also be seen as a dark blue colour (cyanosis) of the lips and fingers. Some patients may develop so-called finger clubbing (swollen ends of fingers) or watch-glass nails (swelling of the finger nails that resembles an hourglass).

A dry cough, a so-called non-productive cough, may be more marked on exercise, in the morning after getting up or during cold weather and is not easily tractable. In some patients, the cough is accompanied by clear to whitish sputum.

Patients with a fibrosing lung disease tend to have frequent infections of the airways and lung. Infection often results in the disease being diagnosed for the first time.

A rather rare symptom of the disease is the so-called door-stop phenomenon. In this, the patient notices that inspiration stops suddenly in a specific position, which the patient is then able to overcome again after a few breaths.

Furthermore, flu-like symptoms such as fatigue, mild fever, weight loss and muscle and joint pain may occur. The symptoms develop gradually over weeks and months and this distinguishes them from the similar symptoms of a cold.

If the lung fibrosis occurs as part of a systemic connective tissue disease (e.g. collagen vascular disease), other complaints and symptoms in other parts of the body and organs can be found, such as blue discolouration of the fingers (so-called Raynaud’s syndrome), dry eyes (sicca symptoms) or difficulties swallowing.

In specific syndromes, there may be an increase in symptoms due to environmental factors, such as in extrinsic allergic alveolitis. This disease is due to sensitisation of the body to certain organic substances (allergens). In this context, antibodies to these substances are formed. Frequent triggers are feathers of pigeons and canaries, fungal spores and certain bacteria. On contact with, or inhalation of, these substances, there is then an increase in symptoms. These symptoms (including watering of the eyes, fever, increased breathlessness) typically occur after a slight delay of about 4 to 8 hours after exposure.