1. Diffuse Parenchymal Lung
Disease
Zunaira Islam MD Pgy2
Dr Eugene Go

2. Diffuse Parenchymal Lung
Disease
 Also previously called Interstitial lung disease (ILD) and
Diffuse Infiltrative Lung disease (DILD)
 Describes 100s of diseases
 no good classification exists, except one that divides
them into Known Cause and Unknown Cause

3. Diffuse … parenchymal… interstitial…
 Diffuse: refers to the nonspecific radiological patterns
 Parenchyma refers to the functioning part of an organ (nephron,
hepatocyte, myocytes) … and Stroma refers to the connective tissue
and supporting structures
 Lung parenchyma in its strictest sense refers solely to alveolar
tissue, respiratory bronchioles, alveolar ducts, terminal bronchioles.
However, the term is often used loosely to refer to any form of
lung tissue
 Many of these diseases involve the alveoli air space as well.

4. Interstitium of lung:
 Airspace Compartment – respiratory bronchioles,
alveolar ducts and alveoli
 Interstitial Compartment – intervening supportive
framework; contains alveolar septa, perivascular and
peribronchial connective tissue
 Cells within the interstitium – fibroblasts, mast cells,
tissue macrophages, lymphocytes
 Type I Pneumocyte – flat and region of gaseous
diffusion; vulnerable to injury
 Type II Pneumocyte – polygonal and site of
surfactant synthesis; can proliferate and reform
alveolar epithelial surface

6. Pathogenesis of interstitial disease:
Often at the end stage most disease processes end in fibrosis from
different often unknown causes. Pathogenesis of Interstitial Fibrosis –
fibrous widening of interstitium is hallmark of chronic interstitial lung
disease
Two Mechanisms:
 (1) Primary interstitial widening – edema and fibrosis formation
directly within the interstitial compartment
eg: interstitial edema, sarcoidosis (thickening of interstitium initially
by granuloma formation)
 (2) Accretion – organization of exudate within the alveolar space that
is converted to fibrous connective tissue and is incorporated into the
interstitium; in some cases the exudate is cleared with resolution.
eg: organizing pneumonia
Hence you see why DPLD is found in the interstitium as well as the
alveolar air-space
This explains the any different radiological findings we will see.

8. Classification of DPLD based on KNOWN vs UNKNOWN cause (only
one so far agreed upon by American and European Societies)
 Connective Tissue Disease  idiopathic interstitial pneumonias:
 Hypersensitivity Pneumonitis  - Idiopathic pulm fibrosis IPF
 Drug Induced (MTX,  -Nonspecific interstitial pna NIP
nitrofurantoin, amiodarone)  - Cryptogenic organizing pna COP
(BOOP)
 Smoking related::
 - Lymphocytic interstitial pna LIP
1- Pulmonary Langerhans ell
Histiocytosis 2- Resp Bronchiolitis  - Acute interstitial pnemonia
Interstitial Lung disease . 3-
Desquamative interstitial pneumonia  Other eosinophilic pnas
 Acute eosinophillic pneumonia  Pulm vasculitides
 Radiation idued  Pulm lympangioleiomyomatosis
 Pulm alveolar proteinosis
 Toxic inhalations (cocaine,zinc in
smoke bombs, amonia)

9. Diagnostic approach
 1- CINICAL CONTEXT
 2- TEMPORAL PROGRESSION
 3- RADIOLOGICAL FINDINGS
 4- HISTOPATHOLOGICAL FINDINGS

10. 1- CLINICAL CONTEXT
Age , sex , occupation, drugs, radiation exposure , CTD ,
physical exam – usually dry crackles

11. 2- TEMPORAL PROGRESSION
Most are slow
Acute ones:
1- usually those that cause alveolar hemorrhage: Vasculitides,
Wegeners , Churg Strauss , microscopic polyangitis
2- Eosinophillic pneumnias – can present as ARDS
3- Acute Interstitial Pna can also present as ARDS without known
cause – called Hamman Rich Syndrome. (Path just shows Diffuse
Alveolar Destruction)
4- Acute exacerbation of known I.P.F (Path will also show Diffuse
Alveolar Damage)

12. 3- RADIOLOGICAL FINDINGS
 By this we mean HIGH RESOLUTION CT SCAN (HRCT)
Pattern:
- Both interstitial and alveolar abnormalities can be seen.
- Interstitial shows up as reticular and reticulonodular /linear /lattice
like presentation
- Alveolr shows up as either consolidation (complete) or ground glass
(partial filling - can still see architecture) opacification
- May have Cystic spaces – specially Langerhans Cell Histocytosis
- May have Nodules – in central lung zone , along perivascular bundle
– Sarcoidosis

13. Radiological findings .. continued
Distribution:
Upper lobes: hypersensitivity, sarcoidosis
Central: pulm alveolar proteinosis , sarcoidosis
Lower lobes: IPF , Asbestosis (As-BASE-tosis)
MOSAIC distribution: nonspecific, ground glass, involving
neighboring lobules, -Due to Vascular disease or Air
trapping - eg. obliterating pnas
Mosaic patterns can be GEOGRAPHICAL: patchy areas
of ground glass, with sharp edges contrasting normal and
abnormal – seen in Resp Bronchiolitis assciated
Interstitial Lung Disease (RBILD)

14. IPF: HRCT of advanced stage of pulmonary fibrosis
demonstrating reticular opacities with honeycombing, with
predominant subpleural distribution.

15. Hypersensitivity pneumonitis: Note the ground-glass
appearance and small nodules.

16. Ill defined centrilobular nodules of ground glass density in a
patient with hypersensitivity pneumonitis

17. Langerhans cell histiocytosis: early nodular stage before the
typical cysts appear

18. Sarcoidosis: Nodules along the fissures indicating a
perilymphatic distribution (red arrows) , with majority of
nodules located along the bronchovascular bundle (yellow
arrow) Nodules in the subpleural region and along the
fissures, specially in upper lobe and perihilar regions -

19. Honeycombing is defined by the presence of small cystic spaces
lined by bronchiolar epithelium with thickened walls composed of
dense fibrous tissue. Honeycombing is the typical feature of usual
interstitial pneumonia UIP – eg seen in IPF

20. Alveolar Proteinosis: Both septal thickening and ground glass opacity in a
patchy distribution. Some lobules are affected and others are not. This
combination of findings is called 'crazy paving'. Crazy paving was thought
to be specific for alveolar proteinosis, but is also seen in many other
diseases such as PCP, bronchoalveolar carcinoma, sarcoidosis,
nonspecific interstitial pneumonia (NSIP), organizing pneumonia (COP),
adult respiratory distress syndrome and pulmonary hemorrhage.

21. Mosaic pattern showing air trapping

22. 4- HISTOPATHOLOGY
 Do only if need to – if it will change the treatment (steroid vs
no steroid)
Common Methods used:
 Bronchoscopy usually provides TINY sample – cannot see
architecture, but CAN still be very helpful in reaching
diagnosis
 VATS video assisted thorascopic surgery: Can be used if
needed , but keep in mind: Mortality rate is high at 2% .
Complication ate is 5-10%

23. Histo-pathological findings:
 Usual interstitial pneumonia Idiopathic pulm fibrosis, CTD associated
(UIP) DPLD , radiation induced DPLD,
Cryptogenic fibrosis Alveolitis
Nonspecific interstitial pneumonia – a
 Nonspecific Interstitial group with poorly characterized HRCT
Pneumonia (NIP) findings – needs further study
 Organising pneumonia Crytogenic Organizing Pneumonia
 Diffuse Alveolar Damage Acute Interstitial Pneumonia,
(DAD) Acute exacerbations of IDP
 Respiratory bronchiolitis Resp Bronchiolitis associated ILD
 Lymphoid Interstitial Lymphoid Interstitial pna
Pneumonia

24.  Usual Interstitial Pneumonitis (UIP) – interstitial
inflammatory infiltrate composed predominantly of
lymphocytes and plasma cells
 Desquamative Interstitial Pneumonitis (DIP) –
characterized by numbers of pigmented macrophages
within alveolar spaces in addition to a usually mild chronic
interstitial infiltrate
 may be more responsive to steroids
 Lymphoid Interstitial Pneumonitis (LIP) – lymphocytes
and plasma cells dominate the cellular infiltrate and rare
much more numerous than in UIP
 often associated with Sjogrens’s syndrome and
dysglobulinemias
 often difficult to distinguish between LIP and lymphoma
involving the lung; LIP can progress to lymphoma

25. Diffuse Alveolar Damage (DAD) – in acute interstitial injury
 seen in Adult respiratory Distress Syndrome (ARDS), Shock
Lung
 sudden onset of respiratory failure with hypoxemia, capillary
permeability and diffuse alveolar infiltrates of CXR
 pts require inspired oxygen concentrations and ventilatory
pressure
Bronchiolitis obliterans : fibrous tissue occlusion of respiratory
bronchioles . Histology – similar to proliferative phase of DAD, but
inflammation is often more intense.
Diffuse alveolar damage (DAD), organizing pneumonia and usual
interstitial pneumonitis (UIP) have similar histological appearances
reflective of the stereotyped response of the lung to a variety of
insults

26. Classification of DPLD based on KNOWN vs UNKNOWN cause (only one so
far agreed upon by American and European Societies)
 Connective Tissue Disease  idiopathic interstitial pneumonias:
 Hypersensitivity Pneumonitis  - Idiopathic pulm fibrosis IPF
 Drug Induced (MTX,  -Nonspecific interstitial pna NIP
nitrofurantoin, amiodarone)
 - Cryptogenic organizing pna COP
 Smoking related:: (BOOP)
1- Pulmonary Langerhans ell  - Lymphocytic interstitial pna LIP
Histiocytosis
 - Acute interstitial pnemonia
2- Resp Bronchiolitis Interstitial
Lung disease  Other eosinophilic pnas
3- Desquamative interstitial  Pulm vasculitides
pneumonia
 Pulm lympangioleiomyomatosis
 Acute eosinophillic pneumonia
 Pulm alveolar proteinosis
 Radiation idued
 Toxic inhalations (cocaine,zinc in
smoke bombs, amonia)

27.  CTD: about 50% pt with RA more common in men, and 75% patients with
scleroderma have chest involvement.
 DRUGS: nitrofurantoin , amiodarone, methotrexate -> care in pts with RA
 RADIATION: Can happen on other side, not necessary in same area, 1-6
months later
 HYPERSENSITIVITY: mold, mold, mold. Mycobacteria in hot-tubs , bird feathers
n droppings, meat serum.
 Lymphangioleiomyomatosis: rare , <1%. Exclusively in women, associated with
tuberous sclerosis in 15%, spontaneous pneumothorax in 55%. Thought to be
estrogen relater but hormonal therapies fail.

28. SMOKING RELATED:
 1- Pulm Langerhans cell Histioctosis (histiocytosis x
/eosinophilic Granuloma) – young. 25% have
pneumothorax. May stabilize.
 2- Resp brnchiolitis RBILD: most smokers,
occaisionally severe, mixed obsrtuctive/restrictive
pattern
 3- Desquamative Interstitial pna: rare, overlap with
RBLID. Steroids may help. Have to stop smoking

29. IDIOPATHIC INTERSTITIAL PNEUMONIAS:
 Nonspecific Interstitial pna (NIP): (Histo-path classification) rare,
overlap with IPF, requires open lung biopsy.
 Cryptogenic Organizing Pna: COP / BOOP : middle aged nonsmokers.
A pneumonia that is not improving – think COP! Biopsy is usually done
with Bronch or VATS. Resolves on its own , steroids may help – or may
recurr durng steroid taper.
 Acute Interstitial Pneumonia: Hamman Rich Syndrome
(This is different cos its acute and can present with fulminant Resp Failure.
Histopath will show Diffuse Alveolar Damage. Poor prognosis – 50%
mortality , no effective therapy so far.)

30.  Thanks !!