Pulmonary Involvement in Autoimmune Diseases

Slide 1 · Pulmonary Involvement in Autoimmune Diseases

Morphologic patterns, systemic associations, and clinicopathologic interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning outcomes

Recognize the pulmonary compartments involved in systemic autoimmune disease.

Differentiate NSIP, UIP, and organizing pneumonia using morphologic principles.

Relate rheumatoid arthritis, systemic sclerosis, lupus, and inflammatory myopathies to characteristic pulmonary patterns.

Explain why both the extent and pattern of disease shape prognosis.

Slide 3 · Systemic autoimmunity can involve several lung compartments

Systemic autoimmune disease

Interstitial tissue

Pneumonitis / fibrosis

Pleura

Pleuritis / effusion

Small airways

Bronchiolitis

Pulmonary vessels

Pulmonary hypertension

Parenchymal nodules

Rheumatoid nodules

Slide 4 · “Connective tissue disease” is a clinical grouping

These systemic autoimmune illnesses often include arthritis or other connective-tissue manifestations.

Lung involvement may emerge at different stages of the systemic disease.

A single autoimmune diagnosis can produce more than one pulmonary injury pattern.

Pulmonary findings must be interpreted in the context of the systemic disorder.

Slide 5 · Autoimmune disorders emphasized in the pulmonary chapter

Rheumatoid arthritis

Pleura, interstitium, nodules, small airways, pulmonary vessels

Systemic sclerosis

Diffuse interstitial fibrosis; Pleural involvement

Systemic lupus erythematosus

Transient infiltrates, pneumonitis, pleuritis, effusions

Dermatomyositis / myositis

Interstitial lung disease in relevant subgroups

Slide 6 · Connective-tissue disease belongs in the fibrosing ILD group

Robbins groups CTD-associated disease among major chronic interstitial lung diseases.

Interstitial inflammation and fibrosis underlie restrictive physiology.

The histologic pattern is an important classifier; The underlying autoimmune disease provides etiologic context.

Advanced fibrosis can make initially different processes appear more similar.

Slide 7 · How interstitial disease impairs lung function

Interstitial injury

Inflammation and/or fibrosis

→

Septal change

Reduced compliance

→

Gas-exchange impairment

Reduced diffusion capacity

→

Clinical expression

Dyspnea and exertional limitation

Slide 8 · Typical clinical signals of chronic interstitial disease

Progressive exertional dyspnea or cough may prompt evaluation.

End-inspiratory crackles are characteristic of the restrictive interstitial group.

Restrictive physiology features reduced lung volumes and compliance.

Reduced diffusion capacity reflects impaired transfer across the alveolar–capillary region.

Slide 9 · Four recurring pulmonary tissue patterns

NSIP

Cellular or relatively uniform fibrosing interstitial injury

UIP

Patchy, temporally heterogeneous fibrosis with remodeling

Organizing pneumonia

Fibroblastic plugs in distal air spaces

Bronchiolitis

Small-airway-centered inflammatory injury

Slide 10 · Pattern is not the same as etiology

Histologic pattern

NSIP / UIP / organizing pneumonia

Describes distribution and morphology

Can occur in multiple clinical settings

Etiologic diagnosis

Rheumatoid arthritis / sclerosis / lupus

Requires clinical and systemic context

Can manifest in several morphologic patterns

Slide 11 · A practical pathology reasoning sequence

Recognize compartment

Interstitium, airspace, airway, pleura or vessel

→

Identify pattern

NSIP, UIP, OP or another process

→

Correlate systemic disease

Autoimmune clinical context

→

Assess consequence

Extent, physiology and progression

Slide 12 · NSIP is especially relevant in autoimmune lung disease

Nonspecific interstitial pneumonia frequently accompanies connective-tissue disease.

Two major tissue patterns are recognized: Cellular NSIP and fibrosing NSIP.

The diagnosis describes an injury pattern, not a unique underlying cause.

Its uniformity contrasts with the heterogeneous scarring typical of UIP.

Slide 13 · Cellular NSIP: Inflammatory expansion of septa

Morphologic meaning

Alveolar septa contain chronic inflammatory cells.

Lymphocytes predominate, with occasional plasma cells.

Inflammatory change may be uniform or patchy.

Conceptual alveolar-septal schematic — not a histologic specimen

Slide 14 · Fibrosing NSIP: Scarring of similar apparent age

Morphologic meaning

Interstitium is thickened by fibrosis.

Fibrotic lesions have a roughly similar appearance and age.

This temporal homogeneity distinguishes NSIP from classic UIP.

Conceptual schematic — does not reproduce a microscopic section

Slide 15 · NSIP has two morphologic components

Cellular pattern

Interstitial lymphocytic inflammation; Limited fibrosis

Fibrosing pattern

More conspicuous fibrosis of relatively uniform age

Shared principle

No diagnostic UIP-type temporal heterogeneity

Clinicopathologic link

Cellular NSIP generally has the more favorable course

Slide 16 · Temporal homogeneity: What it means

Morphologic meaning

Relatively similar-stage interstitial lesions coexist.

Widespread “old and new” scars are not the defining picture.

Homogeneity is a histologic concept, not a precise disease age.

Similar-stage

Similar-stage

Similar-stage

→

→

Temporal homogeneity

Schematic representation of relative lesion age

Slide 17 · NSIP: Radiologic and clinical correlations

Patients commonly have dyspnea and cough over several months.

Bilateral, relatively symmetric lower-lobe reticular opacities.

An underlying autoimmune condition must be sought when NSIP is identified.

Imaging and pathology findings need not specify the exact autoimmune disease.

Slide 18 · Cellular versus fibrosing NSIP

Cellular NSIP

Chronic inflammatory septal expansion

Less extensive scarring

Relatively favorable prognosis

Fibrosing NSIP

Collagen-rich interstitial expansion

More conspicuous architectural stiffness

Less favorable than cellular NSIP

Slide 19 · NSIP and therapeutic response: Pathologic relevance

Some patients with NSIP benefit from immunosuppression.

This observation supports an immune contribution in at least a subset.

Response is not universal and should not be inferred from histology alone.

A CTD-associated NSIP diagnosis should be integrated with clinical severity.

Slide 20 · UIP defines a different fibrosing architecture

Usual interstitial pneumonia shows patchy fibrosis varying by location and maturity.

Relatively preserved alveoli can lie beside heavily scarred lung.

Fibroblastic foci and honeycomb remodeling are characteristic.

UIP is a histologic pattern; Idiopathic pulmonary fibrosis is an etiologic clinical diagnosis.

Slide 21 · UIP: Spatial heterogeneity

Morphologic meaning

Relatively preserved tissue abuts dense scar.

Fibrosis varies from one region to another.

A small sample can miss important diagnostic regions.

Conceptual pattern schematic — not a micrograph

Slide 22 · UIP: Temporal heterogeneity

Morphologic meaning

Early fibroblastic foci and older dense scars coexist.

Lesions of different apparent ages are adjacent.

Contrast with uniform-age fibrosis of fibrosing NSIP.

Earlier focus

Intermediate scar

Established scar

→

→

Temporal heterogeneity

Schematic comparison of fibrotic lesion maturity

Slide 23 · Fibroblastic foci mark active remodeling in UIP

Discrete fibroblast-rich foci appear at advancing edges of fibrosis.

They coexist with established, relatively acellular collagenous scar.

Their presence contributes to temporal heterogeneity.

They are not equivalent to intraluminal Masson bodies in organizing pneumonia.

Slide 24 · Honeycombing represents destroyed alveolar architecture

Morphologic meaning

Dense fibrosis replaces normal alveolar units.

Cystic spaces become lined by epithelial cells.

Architectural distortion signals established remodeling.

Native PowerPoint diagram; Not an image of authentic lung tissue

Slide 25 · NSIP versus UIP: Principal discrimination

NSIP

Relatively uniform lesion age

No characteristic fibroblastic foci

No typical honeycomb pattern

Often more favorable course

UIP

Variable lesion age and location

Fibroblastic foci characteristic

Honeycombing may be present

Typically worse prognosis

Slide 26 · UIP pattern must not be equated automatically with IPF

Idiopathic pulmonary fibrosis is a distinct disease associated with a UIP pattern.

UIP-like morphology may also appear in connective-tissue disease.

Etiologic interpretation requires the systemic history and other data.

Calling all UIP-pattern fibrosis “idiopathic” would miss secondary disease.

Slide 27 · Organizing pneumonia is a response pattern

Organizing pneumonia often follows pulmonary infection or inflammatory injury.

It may occur secondary to connective-tissue disease.

The term “cryptogenic” is appropriate only if an underlying cause is not identified.

Its defining process lies in distal airspaces rather than diffuse mature interstitial scar.

Slide 28 · Organizing pneumonia: Tissue-level sequence

Inflammatory injury

Distal lung response

→

Repair response

Loose fibroblastic tissue forms

→

Airspace occupation

Polypoid plugs within ducts and alveoli

→

Potential resolution

Architecture can remain preserved

Slide 29 · Masson bodies occupy airspaces, not alveolar septa

Morphologic meaning

Loose organizing connective-tissue plugs project into airspaces.

They may involve alveoli, ducts and bronchioles.

Underlying lung architecture remains relatively preserved.

Schematic of organizing pneumonia — not diagnostic histology

Slide 30 · Organizing pneumonia versus UIP

Organizing pneumonia

Intraluminal loose fibroblastic plugs

Lesions of similar maturity

Preserved overall architecture

UIP

Interstitial fibroblastic foci plus fibrosis

Temporal and spatial heterogeneity

Distorted architecture / honeycomb change

Slide 31 · Organizing pneumonia: Clinical–imaging linkage

Cough and dyspnea are common presenting complaints.

Patchy subpleural or peribronchial airspace consolidation may be seen.

The long-term course depends partly on the underlying disease.

A CTD association changes the etiologic designation from cryptogenic to secondary.

Slide 32 · Three fibrosing and organizing patterns at a glance

Interstitial patterns

NSIP: Often uniform

UIP: Heterogeneous with architectural loss

Think alveolar septa

Airspace organizing pattern

Organizing pneumonia: Masson bodies

Preserved underlying framework

Think distal airspace plugs

Slide 33 · Bronchiolitis localizes injury to small airways

Bronchiolitis is one of the recurring pulmonary patterns in autoimmune disease.

An airway-centered process differs conceptually from a primary diffuse interstitial injury.

Symptoms and physiology may reflect small-airway involvement.

The exact bronchiolar subtype matters for pathologic interpretation.

Slide 34 · Follicular bronchiolitis in rheumatoid disease

Morphologic meaning

Rheumatoid arthritis may be associated with follicular bronchiolitis.

The dominant anatomic compartment is the small airway.

A lymphoid-follicle-centered process should not be mislabeled UIP.

Bronchiolar lumen

Teaching schematic of airway-centered inflammation

Slide 35 · Beyond interstitial disease: Pleura and vasculature

Pleuritis

Inflammation of serosal lining

Pleural effusion

Fluid within pleural cavity

Pulmonary hypertension

Vascular complication listed for rheumatoid disease

Compartment matters

Each produces different clinicopathologic findings

Slide 36 · Rheumatoid arthritis can affect lung outside the joints

Rheumatoid arthritis is systemic, despite joint-dominant clinical manifestations.

Pulmonary involvement in approximately 30–40% of patients.

Pleura, interstitium, nodules, bronchioles, and vessels may be involved.

No single pulmonary pattern is unique to rheumatoid arthritis.

Slide 37 · Five pulmonary manifestations of rheumatoid arthritis

1. Chronic pleuritis

With or without effusion

2. Interstitial disease

Pneumonitis and fibrosis

3. Parenchymal nodules

Intrapulmonary rheumatoid nodules

4. Airway injury

Follicular bronchiolitis

5. Vascular disease

Pulmonary hypertension

Slide 38 · Rheumatoid pleuritis is a serosal manifestation

The pleura is a recognized extraarticular target in rheumatoid disease.

Chronic pleural inflammation can occur with or without fluid accumulation.

Pleuritis is anatomically distinct from interstitial pneumonitis.

A patient may have simultaneous pleural and parenchymal disease.

Slide 39 · Why rheumatoid pleural disease requires separate description

Pleural inflammation

Pleuritis

→

Possible fluid formation

Effusion may be present

→

Clinical consequence

Pleural symptoms / restrictive burden

→

Interpretation

Do not infer ILD from effusion alone

Slide 40 · Rheumatoid interstitial pneumonitis may progress to fibrosis

Rheumatoid arthritis can produce diffuse interstitial pneumonitis.

Chronic interstitial injury may be accompanied by established fibrosis.

NSIP and UIP are among autoimmune-associated histologic patterns.

Underlying rheumatoid arthritis changes the interpretation of the same lung pattern.

Slide 41 · Rheumatoid nodules form a focal parenchymal category

Intrapulmonary rheumatoid nodules are an established manifestation of RA.

They should be distinguished from diffuse interstitial fibrosis and small-airway disease.

Tissue examination may be needed when the clinical diagnosis of a nodule is uncertain.

A nodule alone does not determine the overall burden of interstitial disease.

Slide 42 · Rheumatoid nodule: Layered necrobiotic architecture

Morphologic meaning

Typical nodules contain a central zone of fibrinoid necrosis.

Activated macrophages surround the necrotic center.

Lymphocytes and plasma cells form an additional inflammatory component.

Central necrosis

Macrophage rim

Conceptual sectional diagram; Robbins morphology from the RA chapter

Slide 43 · Rheumatoid nodule morphology has a source limitation

The detailed nodule morphology is described principally for extraarticular soft-tissue nodules.

Pulmonary rheumatoid nodules are listed in the lung chapter.

Shared nomenclature supports the teaching analogy, but this is not a substitute for a verified lung photomicrograph.

A specimen must be interpreted by its actual observed features.

Slide 44 · Rheumatoid follicular bronchiolitis targets bronchioles

Follicular bronchiolitis is explicitly named among RA pulmonary manifestations.

Its airway-centered location contrasts with diffuse interstitial fibrosis.

The diagnosis should describe bronchiolar involvement rather than presume every lesion is interstitial.

Multiple compartments may coexist in the same patient.

Slide 45 · Pulmonary hypertension is another rheumatoid complication

Pulmonary hypertension appears in the Robbins list of RA-associated lung manifestations.

It concerns pulmonary vascular pressure and remodeling, not an interstitial pattern by itself.

Vascular disease and parenchymal fibrosis may contribute to pulmonary functional impairment.

The degree and mechanism require clinical evaluation.

Slide 46 · Caplan syndrome links rheumatoid disease and dust exposure

Rheumatoid arthritis

Systemic inflammatory disease

→

Pneumoconiosis

Occupational dust-related disease

→

Coexistence

RA plus pneumoconiosis in lung

→

Designation

Caplan syndrome

Slide 47 · Rheumatoid lung: Compartment-oriented differential

Diffuse process

Interstitial pneumonitis / fibrosis

Small-airway follicular bronchiolitis

Pleural inflammation / effusion

Focal or vascular process

Intrapulmonary rheumatoid nodule

Pulmonary hypertension

Pneumoconiosis overlap (Caplan)

Slide 48 · Systemic sclerosis is a fibrosis-predominant systemic disease

Systemic sclerosis combines chronic autoimmune inflammation, vascular damage, and progressive fibrosis.

Multiple visceral organs, including the lungs, may be affected.

Lung fibrosis contributes to pulmonary insufficiency.

Its pulmonary injury pattern is not identical in every patient.

Slide 49 · Systemic sclerosis: Interconnected pathogenic processes

Immune activation

Profibrotic mediators

→

Microvascular injury

Ischemia and repair

→

Fibroblast activation

Matrix production

→

Tissue outcome

Interstitial and perivascular fibrosis

Slide 50 · Systemic sclerosis-associated ILD often shows NSIP

Diffuse interstitial fibrosis as a pulmonary manifestation.

The NSIP pattern is more common than UIP in systemic sclerosis.

That predominance does not exclude UIP-pattern lung disease.

Recognize the difference between disease association and histologic certainty.

Slide 51 · NSIP and UIP both occur in systemic sclerosis

More common: NSIP

Fibrosis of relatively uniform stage

Often retains more architecture

Supports CTD-associated interstitial pattern

Less common: UIP

Spatial and temporal heterogeneity

Fibroblastic foci and remodeling

Does not imply idiopathic pulmonary fibrosis

Slide 52 · Systemic sclerosis can also involve the pleura

Pleural involvement is explicitly listed in the lung chapter.

It must be assessed independently of the interstitial pattern.

A multisystem fibrosing disease can have simultaneous pleural and parenchymal manifestations.

Pathologic classification should specify the compartment affected.

Slide 53 · Fibrosis links systemic sclerosis to respiratory limitation

Interstitial collagen

Alveolar septal remodeling

→

Mechanical effect

Reduced compliance

→

Gas-exchange effect

Reduced diffusion capacity

→

Systemic impact

Pulmonary insufficiency / right-heart burden

Slide 54 · Systemic lupus erythematosus has varied lung expression

SLE is a systemic autoimmune disease involving immune-complex and antibody-mediated injury.

The lung chapter describes parenchymal infiltrates, severe pneumonitis, pleuritis, and effusions.

Pulmonary involvement may be intermittent or severe.

Its manifestations can span parenchymal and serosal compartments.

Slide 55 · Lupus may cause transient patchy parenchymal infiltrates

Patchy, transient pulmonary infiltrates in SLE.

A transient radiologic infiltrate is not equivalent to fixed fibrotic remodeling.

Activity and distribution help distinguish the clinical process.

Systemic context matters because a radiologic infiltrate is nonspecific.

Slide 56 · Severe lupus pneumonitis is an important exception

Lupus pneumonitis can occasionally be severe.

This is a parenchymal inflammatory manifestation rather than isolated pleural disease.

Severity should not be inferred from the autoimmune diagnosis alone.

The potential for severe injury justifies active clinicopathologic correlation.

Slide 57 · Lupus serositis explains pleuritis and effusions

Systemic autoimmune activity

Immune-mediated serosal injury

→

Pleural inflammation

Pleuritis

→

Associated fluid

Pleural effusion may develop

→

Clinical assessment

Separate serosal from parenchymal involvement

Slide 58 · SLE versus systemic sclerosis: Different emphases

SLE

Patchy / transient infiltrates

Occasionally severe pneumonitis

Pleuritis and effusions

Systemic sclerosis

Diffuse interstitial fibrosis

NSIP more common than UIP

Pleural involvement also possible

Slide 59 · The inflammatory-myopathy spectrum also has pulmonary relevance

The lung chapter includes dermatomyositis–polymyositis among CTD-associated lung diseases.

The skeletal-muscle chapter recognizes a more granular inflammatory-myopathy classification.

Lung disease should be considered within the appropriate myositis subtype.

The older label “polymyositis” should not be assumed to cover all modern subsets.

Slide 60 · Anti-MDA5 dermatomyositis identifies an important ILD phenotype

Some anti-MDA5 dermatomyositis patients develop rapidly progressive ILD.

This pulmonary phenotype is associated with poor prognosis in that subgroup.

Other anti-MDA5 subgroups may have different manifestations and outcomes.

The antibody association is informative but not sufficient to assign the histologic pattern.

Slide 61 · Antisynthetase syndrome links muscle, lung, and joints

Defined by antibodies against aminoacyl–tRNA synthetases.

A prototypical autoantibody is anti-Jo-1; Other antisynthetase antibodies are described.

Muscle involvement, interstitial lung disease, and arthritis are a characteristic constellation.

Recognizing the systemic syndrome can provide the etiologic context for ILD.

Slide 62 · Autoimmune diagnoses and their pulmonary expressions

Disease

Important pulmonary expressions

Rheumatoid arthritis

Pleuritis ± effusion; Interstitial pneumonitis/fibrosis; Nodules; Follicular bronchiolitis; Pulmonary hypertension

Systemic sclerosis

Interstitial fibrosis (NSIP > UIP); Pleural involvement

SLE

Transient infiltrates; Severe pneumonitis; Pleuritis; Pleural effusion

Inflammatory myopathy

ILD in defined subsets (including anti-MDA5 DM and antisynthetase syndrome)

Slide 63 · Classifying by compartment prevents diagnostic shortcuts

Compartment

Descriptive finding

Avoid assuming

Interstitium

NSIP or UIP pattern

Specific autoimmune disease from morphology alone

Distal airspace

Organizing pneumonia

Cryptogenic etiology when CTD present

Bronchiole

Follicular bronchiolitis

Diffuse interstitial fibrosis

Pleura

Pleuritis / effusion

Parenchymal injury is necessarily present

Vessels

Pulmonary hypertension

Primary pulmonary fibrosis

Slide 64 · Integrated assessment of autoimmune-associated ILD

Patient context

Established or suspected autoimmune disease

→

Anatomic pattern

Imaging and functional phenotype

→

Tissue morphology

NSIP / UIP / OP / other if available

→

Risk appraisal

Extent, pattern and clinical trajectory

Slide 65 · Disease extent is a major prognostic determinant

Robbins explicitly links prognosis to the extent of pulmonary involvement.

Extent reflects how much lung is functionally compromised.

A localized pleural or nodular finding is not equivalent to diffuse advanced fibrosis.

Clinical assessment must quantify physiologic and structural impact.

Slide 66 · Histologic pattern also shapes prognosis

The source identifies histologic pattern as an independent prognostic consideration.

NSIP typically has a more favorable prognosis than UIP.

Cellular NSIP generally fares better than fibrosing NSIP.

Advanced architectural destruction can limit reversibility.

Slide 67 · Case discussion: Rheumatoid disease with mixed findings

Case stem

A patient with established rheumatoid arthritis has a pleural effusion and separate diffuse parenchymal abnormalities.

Interpretation

Describe the pleural lesion and parenchymal process separately.

Consider more than one rheumatoid-associated pulmonary phenotype.

Do not diagnose UIP from the clinical label alone.

Slide 68 · Case discussion: Systemic sclerosis and uniform fibrosis

Case stem

A patient with systemic sclerosis has a restrictive pattern. Lung tissue shows interstitial fibrosis of roughly similar age without honeycombing.

Interpretation

The described morphologic pattern favors fibrosing NSIP.

NSIP is more common than UIP in systemic sclerosis.

Link interpretation to disease extent and physiology.

Slide 69 · Case discussion: Lupus with changing infiltrates

Case stem

A patient with SLE develops patchy pulmonary infiltrates that subsequently resolve; Another has pleuritic symptoms and pleural fluid.

Interpretation

Transient parenchymal infiltrates are a recognized lupus finding.

Pleural inflammation/effusion is a separate manifestation.

Clinical severity varies across pulmonary phenotypes.

Slide 70 · Diagnostic challenge: Masson body or fibroblastic focus?

Case stem

A lung lesion contains loose fibroblastic tissue. The critical question is whether it is in an alveolar lumen or within a heterogeneous fibrotic interstitium.

Interpretation

Intraluminal plugs favor organizing pneumonia.

Interstitial fibroblastic foci with heterogeneous scar support UIP.

Location and background architecture are decisive.

Slide 71 · Synthesis: Four principles to retain

Autoimmune diseases can involve interstitium, pleura, airways, nodules and pulmonary vessels.

NSIP, UIP and organizing pneumonia name morphologic patterns, not etiologies.

Rheumatoid arthritis, systemic sclerosis, lupus and myositis have overlapping but distinguishable pulmonary profiles.

Prognosis depends on both the extent and histologic pattern of lung involvement.

Slide 72 · Primary textbook and adjacent context

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. Chapter 15, The Lung: pulmonary involvement in autoimmune diseases, pp. 629–630.

Chapter 15: chronic diffuse interstitial diseases; NSIP, UIP and organizing pneumonia, pp. 627–629.

Chapter 6: systemic lupus erythematosus and systemic sclerosis.

Chapter 26: rheumatoid arthritis and rheumatoid nodules.

Chapter 27: dermatomyositis, antisynthetase syndrome and inflammatory myopathies.