Interstitial lung diseases J84.9

Liebow and Carrington first summarized the group of idiopathic interstitial pneumonia (IIP) based on histological criteria in 1969.

Interstitial lung diseases are chronic inflammations of the lung interstitium involving the alveolar capillary membranes. The consequence of chronic inflammation is an increase in connective tissue structural elements of the lung parenchyma with consecutive lung fibrosis (partly with honeycomb structure).

The current classification of idiopathic interstitial pneumonia was jointly published in 2002 by the American Thoracic Society (ATS) and the European Respiratory Society (ERS), based on the summary prepared by Liebow and Carrington (see above). A distinction is now made:

• Non-specific interstitial pneumonia (NSIP)
• Idiopathic pulmonary fibrosis (IPF), histologically and radiologically the picture of usual interstitial pneumonia (UIP)
• Cryptogenically Organizing Pneumonia (COP)
• Acute interstitial pneumonia (AIP)
• Respiratory bronchiolitis with interstitial lung disease (RB-ILD)
• Desquamative interstitial pneumonia (DIP)
• Lymphocytic interstitial pneumonia (LIP)

IIPs account for half of all interstitial lung diseases.

The prevalence is 67.5 in women and 80.9 in men per 100,000 inhabitants.

Mortality is high in certain subgroups (e.g. IPF 68%), but complete remissions are possible in others.

Primarily a mostly unknown noxious agent leads to chronic epithelial damage, which in turn leads to irregular repair.

In all IIPs we find an activation of fibroblasts, an increase in the connective tissue matrix and a variably pronounced inflammation of the alveolar wall. Nowadays, alveolitis is seen as an accompanying phenomenon and no longer as a primary inflammation.

Addendum:

In patients with rheumatoid arthritis (RA) up to 60% have interstitial lung disease (ILD), which is detected in CT.

According to latest findings, the pathogenesis of RA-ILD and idiopathic pulmonary fibrosis have genetic similarities: The MUC5B promoter variant rs35705950 is associated with RA-ILD and is particularly specific for CT-diagnosed interstitial pneumonia.

This could lead to an earlier diagnosis of ILD in patients with RA and may also have an influence on drug therapy, since drugs that have been shown to be effective in idiopathic pulmonary fibrosis should also be tested in patients with RA-ILD.

literature:

- Juge P-A et al (2018) MUC5B-Promoter Variant and Rheumatoid Arthritis with Interstitial Lung Disease. NEJM379: 2209-2219

Common to all manifestations of interstitial pneumonia is shortness of breath, especially under stress and dry cough. Otherwise, the individual clinical pictures are more or less different.

For more details see the corresponding clinical picture

Nowadays, HRCT plays the primary role in the diagnosis and classification of the individual forms of disease and should always be performed in cases of idiopathic interstitial pneumonia.

The specificity of HRCT is quite high, but the sensitivity is low. It has been shown that if an experienced radiologist considers the diagnosis to be very likely, it is confirmed in about 90% of cases.

If the HRCT does not allow a clear diagnosis to be made, biopsies should be taken from different collection sites. This can be done transbronchially, by a VATS (video-assisted thoracoscopy) or by an open biopsy.

LDL slightly elevated, BSG accelerated, occasionally antinuclear AK or rheumatoid factors slightly elevated

There is a reasonable suspicion of interstitial pneumonia:

• in the case of respiratory distress over a long period of time, especially on exertion, together with an unproductive cough
• familial stress, especially fibrosis
• inspiratory crackling above the base of the lung can be auscultated (in > 80 %) and in advanced fibrosis squeaking/creaking
• FVC reduced in lung function
• significantly limited CO diffusion (can precede the loss of FVC)
• basally accentuated or pleura-edged reticular pattern in the X-ray thorax, but normal findings are also possible (at approx. 10 %)

On average, it takes about 21 months from the onset of the disease to diagnosis.

In the past, surgical lung biopsy was the gold standard for diagnosis. Nowadays, the preferred method of diagnosis is high-resolution computer tomography (HRCT).

• Collagenoses
• Asbestosis
• exogenous allergic alveolitis
• Sarcoidosis (dermatology), Sarcoidosis (internal)

respiratory insufficiency; pulmonary hypertension; cor pulmonale; lung carcinoma;

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