Geography of Chronic Interstitial Lung Disease - A 2024 update

Howard Mann, M.D.

University of Utah School of Medicine

  howard.mann@utah.edu

  howardmann.us

URL: howardm.github.io/GeographyofInterstitialLungDisease

Content

• Imaging features of common chronic, fibrosing interstitial disorders
  • Sarcoidosis and Fibrosing Pneumoconioses
  • Usual Interstitial Pneumonia
  • Fibrotic Non-Specific Interstitial Pneumonia
  • Fibrotic Hypersensitivity Pneumonitis
  • Smoking-Related Interstitial Fibrosis
• Unusual causes of chronic interstitial fibrosis
  • Familial Pulmonary Fibrosis
  • Short Telomere Syndromes (Telemeropathies)
  • Surfactant protein (SP)-C deficiency
  • Pleuropulmonary Fibroelastosis
  • Interstitial fibrosis with non-emphysematous lung cysts
• New concepts in Interstitial Fibrosis
  • Interstitial Lung Abnormalities
  • Progressive Pulmonary Fibrosis
• LIP – R.I.P.

Sarcoidosis

Chronic fibrosing sarcoidosis – Scadding [criteria] Stage IV

• Stage 0: no lung involvement
• Stage I: hilar enlargement alone
• Stage II: hilar enlargement plus interstitial lung disease
• Stage III: interstitial lung disease alone
• Stage IV: lung fibrosis

• upper-lung predominant: typically symmetric, suprahilar opacities
• large opacities associated with surrounding architectural parenchymal distortion-cicatrization atelectasis
• often associated with small nodular disease in adjacent lung and nodal calcifications

Complicated Inorganic Dust (Coal-Silica) Pneumoconiosis

• very similar to sarcoidosis
• occupational history is obviously very important

Some useful findings that may help to distinguish this from sarcoidosis

• cicatricial emphysema (caveat: circumscribed, round cystic spaces may occur in sarcoidosis)
• nodal calcifications typically limited to regional hilar-mediastinal nodes

Accelerated Fibrosing Silicosis

• often described in workers manufacturing engineered stone products
• relatively rapid development of extensive fibrosis

Usual Interstitial Pneumonia

• the most common form of progressive interstitial fibrosis
• the manifestation of “end-stage fibrosis” in many conditions:
  • idiopathic (IPF)
  • connective tissue disease; especially rheumatoid arthritis
  • chronic inhaled dust exposure – asbestosis
  • drug toxicity
  • familial pulmonary fibrosis and genetic syndromes
• it may occur with other forms of fibrosis, e.g., in fibrotic hypersensitivity pneumonitis

Honeycombing and traction bronchiolectasis in UIP CT patterns

honeycombing

traction bronchiolectasis

The evolution of honeycombing in UIP

A plausible explanation

Don’t agonize over honeycombing versus traction bronchiolectasis!

• UIP is present on biopsy in ~ 85% of patients with the Probable UIP CT pattern
• in general, patients with the Typical and Probable CT UIP patterns are not subjected to surgical lung biopsy

An updated algorithm for the diagnosis of IPF

If you insist on agonizing about honeycombing!

Some helpful distinctions in honeycombing of UIP

What’s the pathologic diagnosis ?

The evolution of Fibrotic Non-Specific Interstitial Pneumonitis

Findings

• extensive traction bronchiectasis within diffuse hyperattenuation abnormality (GGO)
• absent or minor subpleural reticulation; no traction bronchiolectasis; no honeycombing

Most common clinical association: connective tissue disease – particularly scleroderma

Fibrosing Lung Disease in Scleroderma

When the following are present, suggest the clinical diagnosis with confidence:

anterior upper lobe sign

exuberant honeycombing sign

straight edge sign

Fibrotic Hypersensitivity Pneumonitis

Typical fibrotic H.P. pattern

Compatible (or is it Indeterminate ?) fibrotic H.P. pattern

CT-pathologic correlation

This is the kind of case that arguably benefits from an ILD - Multidisciplinary Discussion (MDD)

Applying the guidelines for UIP and Fibrotic Hypersensitivity Pneumonitis

It’s often tougher than you might think!

Smoking-related Interstitial Fibrosis

There are three pathologic entities worth knowing about:

• Smoking-Related Interstitial Fibrosis (SRIF)
• Smoking- Related Fibrosis with Airspace Enlargement (AEF)
• Combined Pulmonary Fibrosis-Emphysema Syndrome (CPFE)

SRIF and Diffuse Pulmonary Hyperattenuation (GGO)

• inter-alveolar septal fibrosis with distinctive dark-staining “ropey” collagen (arrows) on H&E staining
• produces ground glass-attenuating opacity on CT
• GGO on CT may represent both
  • smoker’s macrophages and SRIF

From the article:

An example of diffuse, background hyperattenuation abnormality and emphysema

Tip: Compare the lung attenuation with air in central bronchi.

Combined fibrosis-emphysema and airspace enlargement

• CPFE: upper zone emphysema and bibasilar fibrosis, usually an UIP-pattern
• AEF: the cysts are often not sub-pleural and irregular in size and shape.

Unusual causes of chronic interstitial fibrosis

• Familial Pulmonary Fibrosis
  • definition: two or more members of the family
  • any CT pattern of fibrosis may occur, including non-classifiable
• Short Telomere Syndromes (Telemeropathy)
  • suspect this when premature graying, liver dysfunction, and bone marrow “failure” occur.
  • examples: Dyskeratosis Congenita and sporadic TERT (telomerase reverse transcriptase) - related mutations.
• Surfactant protein (SP)-C deficiency
  • usually presents in infancy

Surfactant protein (SP)-C deficiency

Pleuroparenchymal Fibroelastosis

The typical CT pattern:

• apical lung disease
• progressive, confluent reticular opacities with…
• progressive upper zone volume loss

Causes to know:

• sporadic-idiopathic
• chronic allograft dysfunction (CLAD) after lung transplantation
• may occur after stem cell transplantation

Another case of Pleuroparenchymal Fibroelastosis

Don’t confuse this with insignificant Apical Caps.

Interstitial fibrosis with non-emphysematous lung cysts

This is very unusual. You’ll get bonus points (from someone) if you suggest the diagnosis!

• SLE
• COPA syndrome (autosomal dominant)
  • named for the gene mutated in the disease, which encodes the alpha subunit of the coatomer complex-I
  • mention it if the young patient has unexplained arthritis and kidney disease

You’ll get extra bonus points if you remember the acronym!!

COPA syndrome (mutations affect a narrow amino acid stretch in the COPA gene-encoding COPα protein)

Interstitial Lung Abnormalities (ILAs)

ILA is defined as incidental CT findings of nondependent abnormalities affecting more than 5% of any lung zone (ie, upper, middle, and lower lung zones are demarcated by the levels of the inferior aortic arch and right inferior pulmonary vein) at complete or partial chest CT (eg, abdominal or cardiac CT, including lower lung zones) where interstitial disease was not previously suspected.

The findings include ground-glass or reticular abnormalities, lung distortion, traction bronchiectasis or bronchiolectasis, honeycombing, and nonemphysematous cysts

Source:

What should one do if one sees this as an incidental finding ?

Progressive Pulmonary Fibrosis

Surveillance CT in context.

More reasonable approach: Progressive fibrosis is determined on the basis of PFTs (diminshed DLCO and FVC) and CT.

Lymphocytic Interstitial Pneumonitis

The best way to end an ILD talk

Bury a disease entity!