Interstitial Lung Diseases

Firstly, no matter how you get to it, Interstitial Lung Disease causes granulomas. Let’s start off with a definition.

Diffuse Interstitial Lung Disease – a decrease in ventilatory capacity due to fibrosis. 

Common Features of Diffuse Interstitial Lung Disease - Diffuse & Chronic involvement of the pulmonary connective tissue (also known as the interstitium)

o        Ex: when the interstitium is involved in viral pneumonia, it can be considered interstitial lung disease.

§         But because patients get better, this is considered an intermittent interstitial lung disease.

-          Restrictive pattern of pulmonary function test

-          Reduced ability of lung to expand

o        Difficult to take a deep breath and get enough air

o        Patients are always starved for oxygen

-          Reduced oxygen diffusing capacity, reduced lung volumes, and reduced compliance

o        So patient will complain of SOB (don’t get any ideas, that just means “shortness of breath”)

-          Secondary problems such as Pulmonary Hypertension

o        Occurs if the Interstitial Lung Disease continues

o        This will be discussed later on in the week

-          Cor Pulmonale with Right sided heart failure

o        Cor pulmonale is right heart hypertrophy due to lung disorder.

-          End stage lung (honey comb)

o        Will be talked about later in this lecture

Classification of Interstitial Lung Diseases – based on etiology

-          Pneumoconiosis – deposition of organic particles and minerals in the lung to cause a reaction

-          Infectious interstitial pneumonitis – viral, mycobacterial, parsitic, etc.

-          Chemical – Sillo filler’s disease, Bleomycin lung, paraquat, metabolic uremic pneumonitis

o        Bleomycin is a chemotherapeutic agent used to treat cancers, particularly lymphomas.

o        Paraquat – a drug that was used years ago.

-          Physical – radiation pneumonitis

-          Hypersensitivity pneumonitis – immune reaction to the inhalation of certain particulate matter

-          Heart failure can also cause Interstitial Lung Disease.

-          Unknown Etiology

o        Sarcoidosis – granulomatous

§         Some think this it infectious, others don’t.

o        Diffuse Idiopathic Pulmonary Fibrosis (UIP)

o        Desquamative Interstitial Pneumonia (DIP)

o        Eosinophillic Granuloma

o        Wegener’s granulomatosis

Most of these cases (other than viral pneumonia) will come to biopsy, because the physician needs to find out what’s going on so that the patient doesn’t suffer the sequalae.

Pneumoconiosis -  non-neoplastic lung reaction to inhalation of mineral dust, organic dust, and chemical fumes 

Pathogenesis

-          determined by dust concentration, duration of exposure, and effectiveness of the mucocilliary apparatus

o        the mucocilliary apparatus constantly pushes out particulate matter

§         this is where sputum comes from

-          particles 1 – 5 μm reach the terminal small airways and alveoli

o        some get phagocytized by macrophages

§         the mucocilliary apparatus brings all that crap up and you hock it out.

o        Anything bigger than 5 μm gets stuck in the mouth or pharynx and you just cough that out too.

Anthracosis

-          all of us in Newark have this due to pollution

-          the deposition of carbonaceous material in the lungs

-          NO functional impairment (no scarring or destruction)

-          basically, it’s just discoloration

-          found in: coal miners, urban dwellers (us), and tobacco smokers

-          the carbon is ingested by alveolar and interstitial macrophages

-          these carbon-laden macrophages then accumulate along the lymphatics, pleura, and peribronchial/hilar lymphoid tissue.

-          The picture below compares a lung from a non-city dweller (left) with a lung from a city-dweller.

Remember, this carbonaceous material is totally harmless.

Silicosis -  caused by the inhalation of crystals of silicon dioxide (silica)

-          most prevalent occupational disease in the world

-          found among sandblasters, miners, stone cutters

o        especially found in New England, most notably Vermont (“the granite state”)

-          Slowly progressive, nodular, and fibrosing pneumoconiosis

Pathology

-          the lung reacts to the inhaled crystals

o        the result is formation of fibrotic nodules in the lung parenchyma that have concentric laminations and are centered around fixed structures (such as your small bronchioles)

o        Hilar lymph node involvement (with or without calcification)

§         “egg shell” calcification is characteristic

o        Eventually pleural fibrosis and adhesions form

§         This is how you get restrictive disease – by scarring down the lung into fibrotic nodules

§         These nodules can, in time, become confluent

TB and Silicosis are synergistic and TB is a lot more lethal in someone who also has silicosis

 Many pneumoconiosis are registered as simple or complex based on government standards. 

Simple – nodules < 1 cm

Complex – nodules > 1 cm 

-          The reduction in ventilatory capacity and the decrease in diffusing capacity is dependant on the extent of the disease

o        This is what determines if a person can get compensation or file for litigation for being injured on the job.

 Black flat stains – anthracosis

Small holes – emphysema

-          Some of these are signs of retraction emphysema in which the nodule pulls on the alveolar septa as it grows.

Large black raised areas – these are the nodules

-          the nodules toward the bottom of the slide on the whitish smear are becoming confluent.

The whitish line represents scarring of the fissure. 

Below are two pictures that depict what silicosis can do to a lung. The lung on the right is normal, nice and healthy, while the lung on the right is a mess – the interstitium (the brown stuff) is completely destroyed by fibrosis (I guess that’s why it’s brown). As you get this scarring, you also get retraction emphysema due to the pull exerted on the lung by the nodules.

Simple Coal Workers Pneumoconiosis

-          Coal macules – up to 1cm in diameter

o        Associated with respiratory bronchiole

o        Tend to be loose, not dense

o        Results in focal retraction emphysema

-          Dust-laden macrophages in alveoli and lymphatics

-          Dust in lymph nodes results in inflammatory reaction

o        Similar to silicosis

Complicated Coal Workers Pneumoconiosis 

-          Coal macules – greater than 1cm in diameter

-          Chronic inflammation and dense fibrosis

-          Constriction of entrapped structures (bronchi & vessels)

-          Fibrosis of peribronchial and hilar lymph nodes

-          TB is very aggressive

-          Progressive Massive Fibrosis

o        This is a subtype of Complicated Coal Worker’s Pneumoconiosis that involves massive confluence of nodules

-          This leads to death

-          These people are eligible for compensation or litigation. 

The picture above is what Complicated Coal Worker’s Pneumoconiosis looks like. It’s very similar to silicosis: large areas of fibrosis and scars pulling in to result in retraction emphysema. Eventually these nodules will become confluent.

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