Desquamative Interstitial Pneumonia - Causes, Diagnosis, and Treatment

Introduction

Desquamative interstitial pneumonia belongs to a rare group of lung disorders that causes distortion of lung tissue, inflammation, and lung fibrosis. The invasion of mononuclear cells is one of the main characteristics of this disorder. This disorder belongs to the group of disorders known as a major type of idiopathic interstitial pneumonias (IIPs). In 1965 this disorder was first described by LIEBOW et al. Carrington et al. in 1978 first described its association with smoking. Around 90 percent of cases of this disorder are related to smoking. Although according to new studies, nonsmokers show around 40 percent prevalence of such a condition.

What Are the Causes?

The causative factors responsible for desquamative interstitial pneumonia are:

1. Smoking is the main causative factor associated with desquamative interstitial pneumonia. 40 percent of cases are associated with lifetime smokers and 90 percent of cases are linked to smoking. Polycyclic aromatic hydrocarbons (PAHs), benzene, N-nitrosamines, aromatic amines, and aldehydes are responsible for lung tissue irritation and desquamative changes. Apart from this, toxic metal substances like cadmium, chromium, and bismuth are also involved.

2. This is closely related to an occupational hazard. Irritation is caused by toxic substances and toxic gases are associated with these conditions. Ingestion of substances like copper, beryllium, and aluminum by factory workers is closely related to this type of pneumonia. Nylon filaments from the textile industry, powder from fire extinguishers, and diesel fumes are irresponsible for such desquamative conditions.

3. Different medicines such as Sirolimus, Nitrofurantoin, Tocainide, and Sulfasalazine are linked to this condition.

4. Autoimmune conditions like rheumatoid arthritis and scleroderma are considered potential risk factors for desquamative pneumonia. Genetic disorders such as Gaucher disease (a metabolic disorder of lipid metabolism) are linked to this condition.

5. The patient suffering from the human immune virus infection may also suffer from this condition. Aspergillus, Hepatitis C, and Cytomegalovirus infection are also involved in this case.

6. Marijuana, cannabis addiction, and consumption of psychotropic drugs are related to the development of this condition.

What Are the Clinical Features?

This condition is predominantly seen in males. The average age of affected persons is 40-60 years. The symptoms of this condition are:

1. Breathing difficulties during exercise.

2. Gradually the symptoms of breathlessness increase with the progression of the disease.

3. A persistent cough is the main feature of this condition. Cough with thick mucus is also present sometimes. The presence of blood can also be detected in some cases.

On examination, the following features can be observed:

1. Cyanosis: Change in the color of the fingers and the extremities to blue.

2. Bibasilar End Inspiratory Crackles: Bubbling and cracking sounds can be heard at the base of the lungs.

What Are the Diagnostic Procedure?

Different diagnostic procedures are performed for the detection of desquamative interstitial pneumonia. These are:

Imaging Analysis:

• The radiological feature will not be that well defined. In early and asymptomatic cases radiological changes are non-specific. In mild to moderate cases widespread, patchy, ground glass-type opacities can be observed. Along with this sometimes granular or nodular appearance can be seen.

• High-resolution computed tomography (HRCT) imaging is the most commonly used technique for this method. Diffuse ground glass-type opacities can also be seen in this procedure also. The lung involvement is symmetrical. The lower and middle zones of the lung are most commonly affected. Subpleural (space between the pleura and the body of the lungs) involvement is most commonly seen. Parenchymal distortions appear as irregular lines and traction bronchiectasis (early stage of lung fibrosis). Dilated peripheral bronchioles and alveolar ducts can be observed that appear as peripheral microcytes.

Histological Features: As discussed the radiological features are not distinctive. That is why, a biopsy analysis of the lung tissues is done. A surgical biopsy is usually done to collect tissue samples. The histological findings are:

1. Desquamation of the alveolar epithelium can be seen.

2. The most commonly seen histological feature is the presence of macrophages in the alveolar space. The presence of macrophages is extensive, diffuse, and uniform.

3. Infiltrated macrophages usually take up eosinophilic stains. These macrophages usually contain brown, yellow, golden-brown, or black pigmentations. These pigmentations are known as smokers' pigmentations. Such macrophages are called smokers’ macrophages. Golden brown macrophages are usually associated with marijuana addiction.

4. Multinuclear giant cells along with eosinophilic and lymphoid aggregates can also be found. Giant cells are usually detected in patients suffering from occupational hazard-related desquamative pneumonia.

5. Interstitial fibrotic changes, dilatation of the distal airway, and changes similar to emphysema can also be detected.

Lung Function Test: Different lung function tests are performed to analyze the severity of the conditions. These are:

1. Reduction in lung capacity is observed. Also, the mean total lung capacity is also reduced.

2. The carbon monoxide diffusing capacity of the lung is reduced.

3. Oxygen saturation is diminished.

What Are the Treatment Options?

Cessation of smoking and stoppage of the habits are the first part of the treatment. The disease conditions are reversible and the mortality rate in such cases is 6 percent. But untreated patients have a poor prognosis. In mild cases, cessation of smoking, stoppage of drug habits, and reduction in workplace-related irritation may cause a reversal of the condition.

The treatment options include:

1. Long-term systemic steroid application is the most common treatment option. Stoppage of the steroids can cause the reappearance of the symptoms in some cases.

2. Macrolide drugs like clarithromycin can be helpful in the rapid improvement of the patient. Rapid improvement in patients' clinical and radiological parameters can be seen with the application of such drugs.

3. Immunosuppressive drugs like Azathioprine and Methotrexate can also be used to reduce the severity of the infection and for improving clinical symptoms.

4. In severe cases, the only treatment option is lung transplantation.

Conclusion

Desquamative interstitial pneumonia is an extremely rare lung disorder. Somers are mainly affected by this condition. Apart from smoking, drug addiction, auto-immune disorders, and infectious disorders are related to the development of such conditions. Histopathological examination and high-resolution computed tomography (HRCT) can be used for diagnosing such disorders. Long-term application of systemic steroids and macrolides is helpful in curing such conditions.