Patients with interstitial lung disease may initially present with shortness of breath during heavy exertion like jogging, running and climbing flight of stairs. Complains of dry cough may be noted due to the drying of the lungs and throat with chronic fibrosis. Interstitial lung disease may present with fleeting subacute symptomatology which may only last in weeks as exemplified by drug induced and some immune induced diseases [4].

As the disease progresses, difficulty of breathing may now be observable in simple tasks like eating and talking. Chest pain may be infrequent but it must be differentiated with the pain of chest pleurisy [5]. The alteration in the feeding habit may lead to fatigue and significant weight loss. Significant fatigue may diminish respiratory drive causing dyspnea is a characteristic of neuro-muscular disorders that affects the lung [6].

The diminished oxygen uptake may present with a bluish hue in the lips and skin referred to as cyanosis. Edema of the fingernail bed due to lack of oxygenation results in finger clubbing. Auscultation of the lungs will reveal the classic crackling sounds during inhalation and expiration. 

Because of the large number of specific lung diseases falling in the category of restrictive interstitial lung disease, diagnosing the specific pathology may prove to be a difficult task. Chest radiograph in X-ray may reveal the patchy granuloma in Sarcoidosis and the fibrotic changes in systemic pulmonary fibrosis. A serial chest x-ray in time may be a useful tool in monitoring the progression of the disease.

Computed tomography (CT) may reveal the extent of interstitial damage in higher resolution and in cross sectional views. CT-scan is proven to be more sensitive in diagnosing Interstitial lung Diseases caused by silicosis with an accuracy of 93% and interstitial pneumonia in up to 89% [7]. Two dimensional echocardiography can elucidate the size of the right chamber of the heart and measure the concurrent pressure towards the lungs.

Pulmonary function test like spirometry can measure effective lung volume and vital capacity of the lungs which are usually diminished in Interstitial Lung disease. Blood oxygen concentration and saturation can be monitored with the use of a pulse oximeter.

Treadmill or stationary bike stress test may determine your lung functionality while in exercise. Definitive histopathologic evaluation of lung tissue derived from pulmonary lavage, bronchoscopy, and surgical biopsy is an important step in the diagnosis of the lung disease. Immunologic markers like the elevation of Tenascin-C in the serum may indicate fibroblast hyperactivity in the lungs [8].

Idiopathic forms of interstitial lung disease have no known treatment especially those with severe fibrosis. Studies have further indicate that interstitial lung diseases that are idiopathic in origin are unresponsive to corticosterioids or any other medical agents [9].

Immune-mediated interstitial disease like Sarcoidosis may benefit from immunesuppressants in its early course to alleviate symptoms and delay the outcome. Restrictive lung problems which are no longer salvageable may require lung transplant especially those with refractory response to medical therapy [10].

Patients diagnosed with interstitial lung disease are initially subjected for supportive management like oxygen therapy, pulmonary rehabilitation, and dietary counselling

The prognosis in interstitial lung disease appears grim in the idiopathic fibrosis forms. The role of the mesenchymal co-factor Tetrahydrobioterin has been found to perpetually mediate the lung fibrosis in idiopathic variants, making it untreatable [2]. The infiltration types may depend on the stage by which it is diagnosed and brought to medical attention.

Other forms of restrictive lung disease may present as chronic heart failure or hypertension as late complications before the primary interstitial disease of the lung is even diagnosed. In which case, the complications will be the cause of morbidity and mortality of the patients.

Complications

The severe scarring of lung tissues in interstitial lung disease restricts the smaller arteries in the lungs. The increased in pulmonary vascular resistance raises the blood pressure in the lungs referred to as pulmonary hypertension, a serious complication that may lead to right-sided heart failure (Cor pulmonale). Right-sided congested heart failure results when the right ventricle chronically overworks to overcome the vascular resistance of the lungs.

Fibrotic changes in the lung matter increases the incidence of vascular thrombotic event which may be lethal [3]. The end stage disease in interstitial lung disease is pulmonary failure that eventually ensues when the blood exchange to the lungs is severely compromised with impending heart failure. This complication becomes the immediate cause of death in patients with interstitial lung disease.

The majority of interstitial lung disease has unknown or idiopathic causes. A cluster of which are caused by heavy exposure to occupational hazards like coal dusts, silica, grains dusts, talc and even animal droppings. These inhaled infiltrates may cause interstitial lung disease collectively called Pneumoconiosis [1].

An exaggerated immune response in the lung tissues may cause substantial scarring like those in Sarcoidosis. Iatrogenic forms of interstitial lung diseases are observed in patients with past radiation therapy to the chest which usually ensues months after the radiation therapy.

Certain drugs may rarely trigger this restrictive lung disease like Nitrofuranoin, Bleomycin, and Amiodarone.

The idiopathic forms of interstitial lung disease have a higher prevalence rate of 27 to 29 cases per 100,000 persons compared to the intrinsic forms with specific etiology which only represent 3 to 6 cases per 100,000 population.

The risk for interstitial lung disease increases with age reaching up to 175 cases per 100,000 for those patients older than 75 years trailing those age groups between 35-44 years old with a rare penetrance of only 2.7 cases per 100,000 people.

The immune mediated type in Sarcoidosis could reach up to 64 cases out of 100,000 people in Sweden while 10-40 cases per 100,000 populace in North America and Japan.

The mean survival time for patients with idiopathic pulmonary type of lung restriction is usually 3 years or less from diagnosis.

The decrease in respiratory efficiency is brought about by the restrictive nature of fibrotic disease that affects the pleura, lungs and the rib cage concomitantly. The restriction will alter the functional residual capacity of the lungs thus altering the balance in elastic forces that govern inhalation and exhalation.

The eventual hypoxemia is a sign of a ventilation-perfusion mismatch that occurs when the interstitial spaces are infiltrated and compromised. Neuromuscular induced forms of restrictive interstitial lung diseases depresses the central drive for respiration from the level of the brainstem.

In general, patients that develop any lung disease should immediately stop smoking. Studies have demonstrated that interstitial lung disease progresses scarring and edema even with passive smoking; therefore, one should also avoid being near with smokers.

In the late clinical course of the lung disease, muscle wasting may be eminent because of the patient’s difficulty to feed thus a high caloric diet is best given to support nutritional crisis.

Routine flu and pneumonia immunizations can greatly benefit the lungs by preventing inciting factors like infections. High risk groups like coal miners and ship hull workers must wear protective mask to prevent inhalation of the hazardous materials that may infiltrate the lung interstitial spaces.

Interstitial lung disease is a group of restrictive lung disease characterized by massive lung scarring and heavy deposition of hazardous infiltrates in the lung interstitial spaces like asbestos, silica and coal dusts.

The interstitial space is the lacy network of lung cells that allows the veins and arteries to exchange gas with the air sacs (alveoli) of the lungs. The chronic scarring of the tissues restricts the expanding lungs and hampers the oxygenation of the blood. Interstitial lung disease may progress chronically and cause irreversible damage to the lungs requiring lung transplant as its only recourse.

It is imperative that smoking must cease to continue in diagnosed patients and those that are high risk. Interstitial lung disease being a progressive irreversible disease causing persistent discomfort to patients may also cause depression to patients, thus a comprehensive support system must exist in the home to improve the quality of life.

Interstitial lung disease support groups are being formed in the major cities in the United States.

1. Neghab M, Mohraz MH, Hassanzadeh J. Symptoms of respiratory disease and lung functional impairment associated with occupational inhalation exposure to carbon black dust. J Occup Health. Dec 9 2011;53(6):432-8.
2. Almudéver P; Milara J; De Diego A; Serrano-Mollar A; Xaubet A; Perez-Vizcaino F; Cogolludo A; Cortijo J. Role of tetrahydrobiopterin in pulmonary vascular remodelling associated with pulmonary fibrosis. Thorax. 2013; 68(10):938-48
3. Sprunger DB; Olson AL; Huie TJ; Fernandez-Perez ER; Fischer A; Solomon JJ; Brown KK; Swigris JJ. Pulmonary fibrosis is associated with an elevated risk of thromboembolic disease. Pulmonary fibrosis is associated with an elevated risk of thromboembolic disease. Eur Respir J. 2012; 39(1):125-31(ISSN: 1399-3003)
4. Morgenthau AS, Teirstein AS. Sarcoidosis of the upper and lower airways. Expert Rev Respir Med. Dec 2011;5(6):823-33.
5. Gheita TA, Azkalany GS, El-Fishawy HS, Nour Eldin AM. Shrinking lung syndrome in systemic lupus erythematosus patients; clinical characteristics, disease activity and damage. Int J Rheum Dis. Oct 2011;14(4):361-8.
6. Baydur A. Respiratory muscle strength and control of ventilation in patients with neuromuscular disease.Chest. Feb 1991;99(2):330-8
7. Mathieson JR, Mayo JR, Staples CA, Müller NL. Chronic diffuse infiltrative lung disease: comparison of diagnostic accuracy of CT and chest radiography. Radiology. Apr 1989;171(1):111-6.
8. Brissett M; Veraldi KL; Pilewski JM; Medsger TA; Feghali-Bostwick CA. Localized expression of tenascin in systemic sclerosis-associated pulmonary fibrosis and its regulation by insulin-like growth factor binding protein 3. Arthritis Rheum. 2012; 64(1):272-80 (ISSN: 1529-0131).
9. Parambil JG, Myers JL, Ryu JH. Histopathologic features and outcome of patients with acute exacerbation of idiopathic pulmonary fibrosis undergoing surgical lung biopsy. Chest. Nov 2005;128(5):3310-5.
10. Shah NR, Noble P, Jackson RM, et al. A critical assessment of treatment options for idiopathic pulmonary fibrosis. Sarcoidosis Vasc Diffuse Lung Dis. Oct 2005;22(3):167-74