Systemic Sclerosis Scleroderma

Slide 1 · SYSTEMIC SCLEROSIS

(Scleroderma)

Autoimmunity, microvascular injury, and progressive fibrosis

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · What this lecture explains

Recognize the three defining pathologic processes.

Distinguish diffuse and limited cutaneous phenotypes.

Trace vascular and immune injury to organ fibrosis.

Connect tissue morphology with clinical consequences.

Central question

How do small-vessel injury and persistent fibrogenic signaling produce multisystem disease?

Slide 3 · The defining triad

Schematic

Autoimmune inflammation

Small-vessel damage

Progressive fibrosis

Multisystem disease

Interacting processes, not a single proven linear cause

Chronic inflammation is thought to reflect autoimmunity.

Widespread damage involves the microvasculature.

Progressive interstitial and perivascular fibrosis affects skin and viscera.

Slide 4 · “Systemic” is more than skin sclerosis

Schematic

Systemic sclerosis

Skin

GI tract

Kidney

Lung

Heart

Muscle

Sites are representative; Involvement varies by patient

Skin involvement is conspicuous but is not the entire disease.

Gastrointestinal tract, kidney, lung, heart, and muscle may be affected.

Visceral fibrosis and vasculopathy determine many serious complications.

Slide 5 · Two principal cutaneous phenotypes

Diffuse cutaneous disease

Widespread skin involvement near onset

Often rapidly progressive

Visceral involvement commonly early

Limited cutaneous disease

Skin often restricted to fingers, forearms, face

Organ involvement may emerge late

Generally slower and less severe course

Slide 6 · Diffuse disease: Timing matters

Widespread skin change

Relatively rapid progression

Early visceral involvement

Potential organ failure

The cutaneous extent provides a clinical clue to systemic risk.

Extent is not equivalent to a quantitative organ-damage score.

Slide 7 · Limited disease: Late does not mean absent

Skin involvement may remain confined distally for years.

Esophageal and pulmonary vascular disease may develop later.

The source describes a comparatively favorable average course.

Late visceral complications still warrant clinical attention.

Key distinction

Limited cutaneous involvement is not the same as organ-limited disease.

Slide 8 · Diffuse versus limited: Pattern recognition

Feature

Diffuse

Limited

Cutaneous distribution

Widespread early

Fingers, forearms, face

Tempo

Often rapid

Often slower

Visceral involvement

Earlier

Can occur later

CREST phenotype

Not defining

Characteristic association

Slide 9 · CREST: A five-feature clinical pattern

Schematic

C

Calcinosis

R

Raynaud phenomenon

E

Esophageal dysmotility

S

Sclerodactyly

T

Telangiectasia

CREST is a recognized constellation in some patients with limited disease.

The abbreviation denotes manifestations—not five obligatory diagnostic tests.

Cutaneous, vascular, and gastrointestinal processes coexist.

Slide 10 · Calcinosis and telangiectasia

Calcinosis

Subcutaneous calcific deposits

Can be focal or diffuse

Particularly noted with CREST

Telangiectasia

Dilated superficial small vessels

Belongs to CREST constellation

Reflects a vascular component of the phenotype

Slide 11 · Raynaud phenomenon: A vascular clue

Schematic

Baseline digital artery

Episodic vasoconstriction

Maintained flow

Reduced flow

Diagram illustrates functional constriction, not a clinical angiogram

Episodes result from constriction of digital arteries and arterioles.

Numbness and tingling may precede prominent sclerosis.

Vasospasm and structural microangiopathy are related but distinct processes.

Slide 12 · Organ distribution is uneven

Tissue

Principal pathologic process

Clinical consequence

Skin

Dermal sclerosis; vessel loss

Tight skin; limited movement

Esophagus

Muscular atrophy; fibrosis

Hypomotility; reflux

Kidney

Small-artery intimal lesions

Ischemia; hypertension

Lung

Fibrosis; vascular lesions

Respiratory dysfunction

Heart

Fibrosis; arteriolar change

Arrhythmia or failure

Slide 13 · Three interrelated pathogenetic processes

Schematic

Immune activation

Vascular injury

Excess matrix

Organ sclerosis

Interacting processes, not a single proven linear cause

Autoreactive immune responses supply inflammatory mediators.

Endothelial injury generates an obliterative vasculopathy.

Fibroblast activation drives persistent extracellular-matrix deposition.

Slide 14 · The initiating stimulus remains unknown

The cause of systemic sclerosis has not been established.

Unknown external stimuli are proposed in susceptible individuals.

Immune activation and vascular injury may interact from early disease.

The source does not establish a single obligatory causal order.

Interpretive caution

A working model is not proof of the initiating event.

Slide 15 · CD4⁺ T cells in cutaneous lesions

Unidentified antigen?

Activated CD4⁺ T cells

Cytokine release

Fibroblast activation

Activated T cells can be present despite relatively sparse skin inflammation.

The putative inciting antigen has not been established.

Slide 16 · Th2-associated profibrotic signals

Th2 cells have been isolated from affected skin.

Transforming growth factor-β (TGF-β) is profibrotic.

Interleukin-13 (IL-13) can promote matrix-gene expression.

These signals act on fibroblasts rather than directly constituting collagen.

Mechanism

Cytokine signaling changes the transcriptional program of matrix-producing cells.

Slide 17 · How cytokines expand the extracellular matrix

Schematic

TGF-β | IL-13

Activated fibroblast

Collagen + fibronectin

Cytokines promote extracellular-matrix gene expression

TGF-β and IL-13 promote collagen-gene transcription.

Fibronectin and other matrix proteins can also increase.

Accumulated matrix changes tissue architecture and organ compliance.

Slide 18 · Inflammation persists without dense infiltrates

Skin inflammatory infiltrates may be sparse.

Cytokines still recruit and activate leukocytes.

Persistent soluble signals may amplify fibroblast responses.

Absence of florid inflammation does not exclude fibrotic disease.

Histology–biology link

The density of inflammatory cells does not measure prior or ongoing matrix signaling.

Slide 19 · Autoantibodies: Association versus causation

Supported by the source

Antinuclear antibodies are common

Antibody specificity can aid disease recognition

Some profiles correlate with phenotype

Not established

ANAs as the primary fibrotic driver

A proven fibrosis-inducing mechanism for these ANAs

A single antibody sufficient to explain every lesion

Slide 20 · Microangiopathy may be very early

Endothelial activation/injury

Capillary dysfunction

Loss of microvascular lumen

Chronic ischemic damage

The vascular lesion can precede prominent fibrosis.

Whether vascular damage is initiating or secondary remains unresolved.

Slide 21 · Digital arterial intimal proliferation

Schematic

Relatively preserved vessel

Intimal thickening

Wide lumen

Reduced lumen

Original vessel cross-sections — not histology

Small arteries develop intimal thickening.

Luminal narrowing restricts blood flow to distal tissues.

This structural change complements episodic vasoconstriction.

Slide 22 · Capillaries: Dilation, leak, and loss

Schematic

Preserved

Dilated / leaky

Lost / occluded

Conceptual capillary loop changes — no measured patient data

Microvessels may be dilated and abnormally permeable.

Endothelial destruction reduces capillary density.

Progressive vessel loss contributes to chronic tissue hypoperfusion.

Slide 23 · Nailfold capillaries evolve with disease

Schematic

Loop preserved

Loop distorted

Loop obliterated

Conceptual capillary loop changes — no measured patient data

Capillary loops may be distorted early.

Advanced stages may show capillary obliteration.

Morphology makes otherwise hidden microvascular disease clinically visible.

Slide 24 · Biologic evidence of endothelial and platelet activation

Endothelium

Evidence of activation and injury

Increased von Willebrand factor reported

Early capillary and small-artery lesions

Platelets

Increased circulating platelet aggregates

Recruited to endothelial damage

Provide fibrogenic mediators

Slide 25 · Injury and repair amplify perivascular fibrosis

Repeated endothelial injury

Platelet aggregation

PDGF / TGF-β release

Perivascular fibrosis

PDGF = platelet-derived growth factor.

The cycle may continue despite an unidentified primary injury.

Slide 26 · Vascular smooth-muscle abnormalities

Small-vessel smooth muscle shows abnormal responses.

Increased adrenergic receptor expression is described.

Vasoconstriction adds to fixed structural narrowing.

Prolonged perfusion impairment supports tissue injury and repair.

Two contributors

Functional vasospasm + anatomic luminal loss → ischemic burden.

Slide 27 · The final common vascular consequence

Schematic

Microvascular narrowing

Ischemic injury

Repair / scar

Interacting mechanisms and consequences

Microvascular lumen progressively narrows.

Reduced flow causes repeated or sustained ischemia.

Repair of damaged tissues can leave permanent scarring.

Slide 28 · Fibrosis has multiple converging drivers

Schematic

Immune cytokines

Activated fibroblasts

Matrix accumulation

Interacting mechanisms and consequences

Inflammatory cytokines stimulate matrix deposition.

Alternatively activated macrophages may contribute.

Fibroblast hyperresponsiveness and ischemic scarring reinforce deposition.

Slide 29 · Fibroblast hyperresponsiveness

Fibroblasts may react excessively to fibrogenic signals.

Their persistent activation favors matrix over normal architecture.

Clinical sclerosis emerges from net matrix accumulation.

This describes abnormal cell behavior, not a confirmed initiating mutation.

Interpretation

A normal stimulus can yield an abnormal response if the effector cell is hypersensitive.

Slide 30 · Intrinsic fibroblast abnormality: Unresolved

Observation

Cultured patient fibroblasts can make excess collagen

Suggests a cell-intrinsic component

Uncertainty

Causal relationship in vivo remains unclear

Cannot isolate this observation as the sole mechanism

Slide 31 · Immune and vascular pathways converge

Schematic

Inflammation + vasculopathy

Persistent matrix deposition

Organ dysfunction

Interacting mechanisms and consequences

Cytokine-driven fibroblasts increase matrix synthesis.

Vascular ischemia leads to injury followed by repair.

Both pathways support progressive interstitial and perivascular fibrosis.

Slide 32 · Sclerosis is an architectural lesion

Normal tissue is replaced or compressed by excess collagen.

Vascular wall thickening accompanies parenchymal matrix deposition.

Loss of elasticity and tissue-specific function follows.

Morphology must be read together with organ physiology.

Tissue logic

Fibrosis is not merely a visible surface change; It alters the organ substrate.

Slide 33 · Skin: Early inflammatory and vascular changes

Schematic

Early affected skin

Epidermis

Dermis

Subcutis

Perivascular immune cells and early vascular injury

Early lesions may contain perivascular CD4⁺ lymphocytes and edema.

Collagen can become conspicuously eosinophilic.

Small vessels show endothelial damage and basal-lamina thickening.

Slide 34 · Skin: Progressive dermal sclerosis

Schematic

Established sclerosis

Epidermis

Dermis

Subcutis

Compacted dermal collagen with architectural attenuation

Dense compact collagen progressively fills the dermis.

Fibrotic dermis becomes adherent to deeper subcutaneous tissue.

Skin stiffness and retraction follow loss of normal architecture.

Slide 35 · Epidermis and appendages change secondarily

Epidermal thinning and rete-peg loss may be present.

Dermal appendages undergo atrophy.

Compact collagen dominates the dermal compartment.

These changes together explain tight, atrophic skin.

Histologic combination

Sclerosis + appendage loss + epidermal thinning, not simply increased collagen alone.

Slide 36 · Dermal arterioles and capillaries

Schematic

Relatively preserved vessel

Intimal thickening

Wide lumen

Reduced lumen

Original vessel cross-sections — not histology

Hyaline thickening of dermal vascular walls is described.

Endothelial damage coexists with narrowing or partial occlusion.

Dermal microangiopathy helps explain ischemic cutaneous changes.

Slide 37 · Advanced skin disease: Clinical consequence

Dense dermal collagen

Adhesion to deeper tissue

Skin contraction

Restricted joint motion

Finger tapering and a clawlike posture can occur.

Facial tightening may produce a masklike appearance.

Slide 38 · Digital ischemia causes tissue loss

Schematic

Convergent digital injuries

Narrowed digital vessels

Distal ischemia

Ulceration • terminal atrophy • tissue loss

Impaired blood supply can lead to digital ulcers.

Terminal phalanges may undergo atrophy.

Severe distal damage can culminate in autoamputation.

Slide 39 · Cutaneous progression: Early to advanced

Stage

Microscopic emphasis

Clinical expression

Early

Perivascular inflammation; edema

Raynaud / evolving swelling

Established

Increasing compact dermal collagen

Skin tightening; reduced mobility

Advanced

Appendage loss; vascular obliteration

Atrophy; ulcers; contracture

Slide 40 · The gastrointestinal tract is frequently involved

Gastrointestinal involvement in ~90% of patients.

Progressive muscular atrophy and fibrosis may occur at several levels.

Esophageal disease is especially conspicuous.

Dysphagia, reflux, and malabsorption reflect organ-specific lesions.

Mechanism

Muscular replacement by collagen impairs propulsion and sphincter function.

Slide 41 · Esophagus: Atrophic muscularis and fibrosis

Schematic

Normal wall

Fibrotic muscularis

Motility preserved

Hypomotility

Muscle replacement is schematic; Lumen size is illustrative only

Lower esophageal segments are particularly vulnerable.

The muscularis is replaced by collagenous fibrosis.

Reduced compliance and dysmotility impair bolus movement.

Slide 42 · Esophageal dysfunction creates reflux injury

Muscular fibrosis

Lower sphincter dysfunction

Gastroesophageal reflux

Esophagitis / stricture / Barrett esophagus

The resulting mucosal pathology is a consequence of motility failure.

This is a causal teaching chain, not a universal sequence in every patient.

Slide 43 · Mucosal and submucosal changes

Esophageal mucosa may be thinned or ulcerated.

Lamina propria and submucosa can show excessive collagen.

Mucosal injury combines with abnormal propulsion and reflux.

Lower-esophageal dilatation may develop with atony.

Pathology correlation

Muscle disease and mucosal lesions coexist through different mechanisms.

Slide 44 · Small-bowel disease: Malabsorption

Schematic

Preserved villi

Villus loss / flattening

Simplified villus architecture, not tissue microscopy

Small-intestinal involvement can impair absorptive function.

Loss of villi and microvilli is described in the source.

Malabsorption may produce weight loss and nutritional anemia.

Slide 45 · Early joints: Inflammatory synovitis

Inflammation can produce synovial hypertrophy and hyperplasia.

Early joint changes may resemble rheumatoid arthritis.

That destructive arthritis is uncommon.

Later fibrosis alters mobility and soft-tissue function.

Differential teaching point

Similar synovitis does not imply the same degree of joint destruction.

Slide 46 · Musculoskeletal disease changes with stage

Earlier

Synovial inflammation

Hypertrophy and hyperplasia

Inflammatory changes occur before later fibrosis

Later

Fibrous change is more conspicuous

Restricted mobility and contracture

Erosive joint destruction is not a hallmark

Slide 47 · Inflammatory myositis is a recognized subset

Inflammatory myositis in a minority of patients (~10%).

Muscle weakness need not be explained entirely by skin contracture.

This demonstrates an additional immune-mediated tissue target.

Inflammatory myopathy as a separate disease family lies outside this unit.

Scope

Recognize overlap without substituting a full lecture on inflammatory myopathies.

Slide 48 · Renal injury predominantly affects vessels

Schematic

Relatively preserved vessel

Intimal thickening

Wide lumen

Reduced lumen

Original vessel cross-sections — not histology

Renal vascular lesions are more characteristic than a specific glomerular pattern.

Interlobular arteries develop thickened intima and reduced lumen.

Ischemic vascular injury underlies dangerous renal presentations.

Slide 49 · Concentric renal intimal change

Schematic

Relatively preserved vessel

Intimal thickening

Wide lumen

Reduced lumen

Original vessel cross-sections — not histology

Intimal accumulation includes mucinous or collagenous material.

Concentric intimal-cell proliferation can narrow the lumen.

The changes may resemble lesions associated with severe hypertension.

Slide 50 · Hypertension can accelerate renal vascular injury

Small-artery narrowing

Renal ischemia

Rapidly severe hypertension

Arteriolar necrosis / thrombosis / infarction

The source describes a severe, rapidly progressive hypertensive subset.

Not every patient with renal vascular lesions is hypertensive.

Slide 51 · Scleroderma renal disease: What to recognize

Primary lesion

Vascular intimal thickening

Luminal compromise and ischemia

No specific glomerular lesion

Dangerous progression

Severe hypertension

Fibrinoid arteriolar necrosis

Thrombosis and renal failure

Slide 52 · Lungs: Two major pathologic pathways

Schematic

Interstitial process

Vascular process

Fibrosis

High resistance

Pulmonary interstitial fibrosis impairs lung function.

Pulmonary vascular dysfunction can produce hypertension.

Parenchymal and vascular injury may coexist but are distinct lesions.

Slide 53 · Pulmonary interstitial fibrosis

The source reports pulmonary involvement in more than half of patients.

Interstitial scarring alters the alveolar support framework.

Fibrotic morphology may resemble idiopathic pulmonary fibrosis.

Respiratory insufficiency is a major clinical consequence.

Morphologic limitation

Histology alone may not identify systemic sclerosis as the cause of fibrosis.

Slide 54 · Pulmonary hypertension: Vascular mechanism

Pulmonary endothelial dysfunction

Vasospasm / remodeling

Increased pulmonary vascular resistance

Pulmonary hypertension

This is a vascular pathway, not simply a synonym for interstitial fibrosis.

Cardiac effects can develop from the increased pulmonary pressure.

Slide 55 · Pulmonary fibrosis and hypertension are not interchangeable

Question

Interstitial fibrosis

Pulmonary vascular disease

Primary compartment

Interstitium / parenchyma

Pulmonary microvasculature

Mechanism

Matrix accumulation

Endothelial injury; vasospasm

Functional result

Restricted gas exchange

Raised vascular resistance

Clinical overlap

May coexist with vascular disease

May coexist with parenchymal fibrosis

Slide 56 · Heart: Three types of reported lesions

Schematic

Pericarditis + effusion

Myocardial fibrosis

Arteriolar thickening

Pericarditis may be accompanied by effusion.

Myocardial fibrosis alters the cardiac muscle substrate.

Small intramyocardial arteries can develop wall thickening.

Slide 57 · Myocardial pathology explains functional impairment

Myocardial fibrosis can contribute to arrhythmia.

Diffuse or focal dysfunction may culminate in cardiac failure.

Pulmonary disease may impose an additional right-heart burden.

Morphologic myocardial involvement may exceed symptomatic involvement.

Clinicopathologic distinction

Direct myocardial injury and secondary right-heart stress have different causes.

Slide 58 · A multisystem lesion-to-symptom map

Structural lesion

Physiologic effect

Clinical clue

Dermal collagen increase

Skin contraction

Sclerodactyly

Digital arterial disease

Distal ischemia

Raynaud; ulcer

Esophageal muscle fibrosis

Poor motility

Dysphagia; reflux

Renal arterial disease

Renal ischemia

Hypertension / renal failure

Pulmonary scarring

Reduced respiratory function

Dyspnea

Slide 59 · Clinical presentation: Demographic pattern

A female-to-male ratio of approximately 3:1.

Peak incidence is described in the 50- to 60-year age group.

Clinical recognition rests on the syndrome and its organ pattern.

Population figures are descriptive, not diagnostic criteria.

Use appropriately

Demographics change pretest expectation; They cannot establish or exclude disease.

Slide 60 · Antinuclear antibodies: Role in evaluation

Antinuclear antibodies are frequent in systemic sclerosis.

Their antigen specificity provides phenotypic information.

Antibody status should be integrated with skin and organ findings.

The pathogenic role of common ANAs remains incompletely resolved.

Three uses to separate

Diagnostic association ≠ prognostic correlation ≠ proven pathogenic mechanism.

Slide 61 · Anti–topoisomerase I (anti–Scl-70)

Recognition

Targets DNA topoisomerase I

Described as highly specific

Associated with diffuse disease

Clinicopathologic correlation

Pulmonary fibrosis more likely

Peripheral vascular disease association

Frequency varies with population and assay

Slide 62 · Anticentromere antibodies

Recognition

Associated with limited phenotype

Often seen with CREST pattern

Correlates with a different clinical course

Clinical significance

Visceral involvement may occur later

Late pulmonary hypertension remains possible

Does not imply complete absence of internal disease

Slide 63 · Two antibodies: Do not overinterpret

Characteristic

Anti–topoisomerase I

Anticentromere

Typical phenotype

Diffuse more often

Limited / CREST more often

Important association

Interstitial lung / vascular disease

Limited skin; late organ disease

Interpretive role

Phenotypic / prognostic marker

Phenotypic / prognostic marker

Not proof of

Antibody-driven fibrosis

No future visceral disease

Slide 64 · The clinical diagnosis is an integrated pattern

Schematic

Skin phenotype

Vascular / organ findings

Antibody profile

Integrated clinicopathologic assessment

Skin distribution establishes a major phenotypic clue.

Raynaud and microvascular features reveal early vascular disease.

Visceral manifestations and antibody profiles refine the picture.

Slide 65 · Overlap disorders: Avoid a single-feature diagnosis

Some features overlap with systemic lupus erythematosus.

Synovial inflammation overlaps clinically with rheumatoid arthritis.

Inflammatory muscle disease can overlap with myositis.

The combination of sclerosis and microangiopathy is more distinctive.

Boundary

This lecture does not replace disease-specific classification criteria.

Slide 66 · Case: Progressive skin tightness

Hypothetical vignette: A patient develops rapid extension of skin tightening beyond the hands, followed by dysphagia and respiratory symptoms.

Which phenotypic pattern is most consistent?

Reasoning

Diffuse cutaneous disease is favored by proximal early spread.

Early visceral symptoms reinforce a higher-risk pattern.

Skin distribution alone does not prove a particular visceral lesion.

Slide 67 · Case: Distal skin disease with CREST features

Hypothetical vignette: Long-standing Raynaud episodes are followed by distal skin tightening, calcific deposits, and esophageal dysmotility.

Which clinical constellation does this illustrate?

Reasoning

A limited cutaneous / CREST-associated pattern is plausible.

Raynaud illustrates vascular dysfunction; Dysmotility reflects tissue disease.

A limited skin phenotype does not exclude later organ involvement.

Slide 68 · Case: Abrupt renal deterioration

Hypothetical vignette: In a patient with established skin sclerosis, blood pressure increases rapidly as renal function declines.

Which tissue lesion is the major mechanistic concern?

Reasoning

Renal small-artery intimal and arteriolar vascular injury.

Luminal compromise may intensify ischemia and severe hypertension.

The source does not define a specific primary glomerular lesion.

Slide 69 · Case: Two mechanisms of dyspnea

Hypothetical vignette: A person with systemic sclerosis develops progressive dyspnea; The lecture identifies both parenchymal and vascular pulmonary lesions.

Which two distinct processes should be considered?

Reasoning

Interstitial lung fibrosis affecting parenchymal structure.

Pulmonary vasculopathy contributing to pulmonary hypertension.

The two processes are mechanistically distinct and may coexist.

Slide 70 · Sequence: Microvascular disease to tissue loss

Capillary injury and dropout

Progressive vessel narrowing

Tissue ischemia

Ulceration / atrophy

This explains digital injury without attributing every lesion to inflammation.

Episodic Raynaud is an early, functional component of vascular disease.

Slide 71 · Sequence: Cytokines to sclerotic organ failure

CD4⁺ / Th2 activation

TGF-β and IL-13

Fibroblast matrix synthesis

Loss of organ compliance

Cytokine activation and chronic repair reinforce one another.

The same general lesion has organ-specific physiologic consequences.

Slide 72 · The essential diagnostic distinctions

Do not confuse

With

Why the difference matters

Limited skin disease

Absence of systemic disease

Viscera can be affected late

Raynaud vasospasm

Only vascular mechanism

Fixed obliterative lesions also occur

Positive ANA

Proven cause of fibrosis

Causation not established

Pulmonary fibrosis

Pulmonary hypertension

Distinct primary compartments

Renal disease

Primary glomerulonephritis

Vascular lesions dominate

Slide 73 · Mechanism-to-morphology synthesis

Schematic

Immune activation

Vascular injury

Organ sclerosis

Interacting mechanisms and consequences

Early endothelial injury narrows and depletes small vessels.

Immune-derived cytokines promote fibroblast matrix production.

Progressive sclerosis and ischemia disrupt organ-specific function.

Slide 74 · Five lasting clinicopathologic principles

Systemic sclerosis combines autoimmunity, vasculopathy, and fibrosis.

Diffuse versus limited phenotypes chiefly differ in distribution and timing.

Organ manifestations follow the compartment injured in each tissue.

Antibody associations aid interpretation but do not prove causality.

Synthesis

Recognize the vascular and fibrotic processes together—not as competing explanations.

Slide 75 · Source and scope

Robbins, Cotran & Kumar: Pathologic Basis of Disease, 11th edition (2026).

Chapter 6, Diseases of the Immune System: Systemic Sclerosis (Scleroderma), pp. 204–206.

Diagrams are original editable teaching schematics, not diagnostic microscopy.

Clinical vignettes are hypothetical and illustrate the textbook mechanisms.