Epidermolysis Bullosa and Porphyria

Slide 1 · Epidermolysis Bullosa and Porphyria

Noninflammatory blistering disorders

Mechanical failure of skin adhesion and porphyrin-associated cutaneous injury

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Localize a blister to the epidermis, lamina lucida, or sublamina-densa compartment.

Explain how KRT5/KRT14, laminin, BPAG2, and COL7A1 defects produce distinct EB forms.

Recognize the cutaneous and microscopic findings described for porphyria.

Distinguish inherited and metabolic bullous disease from autoimmune blistering disorders.

Slide 3 · Why the blister plane matters

A blister is a structural lesion with a localizable level.

Anatomical attachment fails

Keratinocytes or basement-membrane layers separate

A vesicle or bulla forms

Depth helps classify the disorder

Localize first; Infer mechanism second.

Slide 4 · Skin adhesion: Five relevant compartments

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

Basal keratinocytes contain intracellular keratin filaments.

Hemidesmosomes attach basal cells to the underlying basement membrane.

Lamina lucida, lamina densa, and anchoring fibrils transmit the attachment toward dermis.

Slide 5 · Two routes to skin fragility

Mechanical route

Inherited structural-protein defect

Pressure or friction triggers cleavage

Epidermolysis bullosa

Metabolic route

Porphyrin-metabolism disturbance

Sunlight exacerbates the cutaneous reaction

Porphyria-associated blistering

Slide 6 · Inherited disease versus autoantibody disease

The same attachment system can fail through genetic or immunologic mechanisms.

Disorder

Dominant mechanism

Representative target

Epidermolysis bullosa

Inherited structural weakness

Keratin / laminin / collagen VII

Bullous pemphigoid

Autoantibody to attachment proteins

BPAG2

Pemphigus

Autoantibody-mediated cell-cell detachment

Desmogleins

Dermatitis herpetiformis

IgA-associated subepidermal injury

Anchoring-region components

Slide 7 · Clinical provocation: Friction or light?

Pressure / rubbing

Characteristic of inherited EB

Onset at or soon after birth

Mechanical sites are especially vulnerable

Sun exposure

Exacerbates porphyria-associated lesions

May accompany urticaria and vesicles

Scarring may follow

Slide 8 · A structured morphology approach

Subepidermal location alone is not specific to a single disease.

Determine cleavage plane

Evaluate inflammatory accompaniment

Link the findings to exposure and onset

Use localization to interpret the candidate defect

Slide 9 · Epidermolysis bullosa: Disease definition

An umbrella term for inherited defects in proteins essential for skin mechanical stability.

The shared phenotype is blistering after minor pressure, rubbing, or trauma.

The various forms are defined in large part by the level and molecular basis of cleavage.

Slide 10 · Presentation at or soon after birth

A clinical clue, not a genotype.

Characteristic blister susceptibility is present at or shortly after birth.

Minor trauma can have a disproportionate effect in structurally fragile skin.

Early onset supports a hereditary fragility mechanism but does not identify the subtype.

Slide 11 · From mechanical force to a blister

Different mutated proteins create different cleavage planes.

Pressure or rubbing on skin

A compromised structural link bears the stress

Epidermal attachment fails at its weak level

Fluid collects across the plane of separation

Slide 12 · Major EB forms map to different layers

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplex

Junctional

Dystrophic

Simplified anatomical schematic

Simplex: Defect within basal epidermal keratinocytes.

Junctional: Cleavage at the lamina lucida.

Dystrophic: Cleavage beneath the lamina densa.

Slide 13 · EB simplex: Basal-layer cleavage

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

Defect affects the basal cell layer of the epidermis.

Keratin 5 and keratin 14 are the principal gene products identified.

The disturbance is intracellular rather than a lamina-lucida split.

Slide 14 · Keratin 5 and keratin 14 function as a pair

The two partners are required to build the same structural apparatus.

Keratin 5 protein

Pairs with keratin 14

Functional basal-cell keratin fiber

Provides mechanical support within basal keratinocytes

Slide 15 · Why either KRT5 or KRT14 can cause EB simplex

A shared fiber explains overlapping clinical effects.

KRT5 mutation

Alters a partner of the basal keratin pair

Disrupts keratin-fiber function

KRT14 mutation

Alters the other partner of the same pair

Can produce a similar phenotype

Slide 16 · Dominant-negative keratin effect

Dominant-negative activity as the basis of common dominant transmission.

Mutant keratin protein is made

The mutant product interferes with the functioning filament system

Basal keratinocytes lose mechanical resilience

Minor stress causes basal-cell cleavage

Slide 17 · Inheritance of classic EB simplex

Typical pattern

Autosomal dominant

Molecular explanation

Dominant-negative activity of mutant keratin

Clinical implication

A single pathogenic allele may disrupt a shared filament system

Slide 18 · EB simplex is the most common EB group

Textbook frequency: Subtype proportion, not population incidence.

Robbins assigns approximately 75%–85% of EB cases to the simplex type.

The common molecular basis is mutation of keratin 5 or 14.

Frequency does not replace cleavage-plane or molecular assessment in an individual case.

Slide 19 · Recognizing basal-cell injury in EB simplex

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

The cleavage localizes to the basal epidermal compartment.

The level is distinct from lamina-lucida or sublamina-densa failure.

Very subtle findings may require ultrastructural characterization.

Slide 20 · Basal-cell versus basement-membrane failure

Intracellular keratin defect

KRT5/KRT14

Simplex EB

Basal epidermis

Extracellular attachment defect

Laminin or type VII collagen

Junctional or dystrophic EB

Basement-membrane region

Slide 21 · Junctional EB: Lamina-lucida cleavage

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

The separation occurs at the level of the lamina lucida.

Overlying skin may appear otherwise histologically normal.

Subepidermal separation need not be accompanied by inflammation.

Slide 22 · The lamina lucida as a junctional interface

It is a specialized compartment beneath basal keratinocytes.

Laminin contributes to binding hemidesmosomes and anchoring filaments.

Defective links here permit the epidermis to separate despite otherwise preserved epidermal architecture.

Slide 23 · Laminin bridges the epidermal attachment apparatus

Loss of laminin function weakens the junctional adhesive bridge.

Hemidesmosomes of basal cells

Laminin-containing lamina-lucida connection

Anchoring-filament attachment

Continuity between epidermis and basement membrane

Slide 24 · Laminin-subunit mutations in junctional EB

Most junctional EB cases in the source result from laminin-subunit defects.

These defects are usually inherited in an autosomal recessive pattern.

The relevant dysfunction occurs at the level of the lamina lucida.

Slide 25 · BPAG2 mutations: An alternative junctional cause

BPAG2 mutations in a subset of junctional EB.

BPAG2 is a hemidesmosomal structural protein.

Genetic loss of function and antibody targeting of the same protein have different etiologic bases.

Slide 26 · BPAG2 illustrates genetic and immune mechanisms

Junctional epidermolysis bullosa

Inherited BPAG2 defect

Structural adhesion weakness

Blistering without a necessary inflammatory autoimmune mechanism

Bullous pemphigoid

Autoantibodies to BPAG2

Complement and inflammatory recruitment

Subepidermal blister

Slide 27 · Junctional EB: Characteristic noninflammatory split

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

A subepidermal blister at the lamina lucida.

The illustrated lesion has no associated inflammation.

Absence of inflammation supports a structural disease mechanism in this context.

Slide 28 · Clinical morphology of junctional EB

An illustrative Robbins case shows erosions in flexural creases.

Erosions are compatible with mechanically fragile skin exposed to friction.

Clinical distribution helps identify vulnerable regions but is not a precise cleavage-plane test.

Slide 29 · Dystrophic EB: A deeper cleavage plane

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

Blisters form beneath the lamina densa.

The associated anchoring fibrils are rudimentary or defective.

This deeper defect is associated with scarring forms of EB.

Slide 30 · Anchoring fibrils secure epidermis to dermis

Anchoring fibrils extend below the lamina densa into dermal attachment structures.

Type VII collagen is a major component of these fibrils.

Deficiency shifts the weak point beneath the dense basement-membrane layer.

Slide 31 · COL7A1 to dystrophic EB

A direct gene → structural protein → cleavage-plane relationship.

COL7A1 mutation

Altered type VII collagen

Defective anchoring fibrils

Cleavage below lamina densa and scarring tendency

Slide 32 · Dystrophic EB can have two inheritance modes

The inheritance mode is mutation-dependent; Do not assume one pattern for all dystrophic EB.

Dominant dystrophic EB

Certain COL7A1 mutations

Autosomal dominant transmission

Recessive dystrophic EB

Other COL7A1 mutations

Autosomal recessive transmission

Slide 33 · Why deeper separation may be associated with scarring

The textbook specifically associates dystrophic EB with scarring.

Defective anchoring-fibril zone

Sub-lamina-densa separation

Damage extends into superficial dermal attachment

Healing may leave a scar

Slide 34 · Junctional versus dystrophic EB

Junctional

Lamina-lucida cleavage

Laminin or BPAG2 defects

Often autosomal recessive laminin lesions

Dystrophic

Cleavage below lamina densa

COL7A1 / type VII collagen

Dominant or recessive

Slide 35 · Mixed EB forms are recognized

Not all inherited EB falls cleanly within one single plane.

Mixed types show defects at several anatomical levels.

A simple three-category scheme is a useful first model, not an exhaustive description of every case.

Slide 36 · EB anatomy-to-gene synthesis

Subtype

Weak compartment

Representative molecular lesion

Inheritance described

Simplex

Basal cell layer

KRT5 or KRT14

Usually AD

Junctional

Lamina lucida

Laminin subunits; Sometimes BPAG2

Usually AR for laminin defects

Dystrophic

Below lamina densa

COL7A1 (collagen VII)

AD or AR

Mixed

Multiple levels

Not specified in excerpt

Not specified

Slide 37 · Why routine histology may not subtype EB

Histologic changes can be extremely subtle.

Cleavage-depth distinctions may require electron microscopy.

A generic “subepidermal blister” report may not distinguish lamina lucida from below-lamina-densa separation.

Slide 38 · Logical interpretation of an EB specimen

This is an explanatory framework, not a substitute for a formal diagnostic testing protocol.

Clinical blistering from early life and minor trauma

Microscopy identifies the epidermal–dermal separation

Ultrastructure can refine the cleavage level

Molecular relationships suggest the relevant protein system

Slide 39 · Case: A basal keratin defect

Constructed teaching vignette

An infant develops blisters at points of rubbing. A pathogenic KRT14 variant is identified.

Which attachment compartment is primarily impaired?

Interpretation

Basal keratinocyte filament system

KRT14 pairs with keratin 5 in EB simplex.

Slide 40 · Case: Lamina-lucida cleavage

Constructed teaching vignette

A skin sample shows a noninflammatory separation at the lamina lucida.

Which EB class and molecular system best fit?

Interpretation

Junctional EB; Laminin or selected hemidesmosomal proteins

The cleavage plane corresponds to the lamina lucida.

Slide 41 · Case: Type VII collagen

Constructed teaching vignette

Inherited skin fragility is accompanied by a COL7A1 variant and sublamina-densa blistering.

Which EB type is implicated?

Interpretation

Dystrophic EB

Type VII collagen forms basement-membrane anchoring fibrils.

Slide 42 · Porphyria: The central definition

Porphyrias are uncommon inherited or acquired disturbances of porphyrin metabolism.

They are biochemical disease groups that may include important cutaneous manifestations.

The skin pathology is considered separately from inherited defects of adhesion proteins.

Slide 43 · Where porphyrins normally participate

These three physiological contexts for porphyrins.

Hemoglobin

Porphyrin-containing heme supports oxygen transport.

Myoglobin

The heme group participates in oxygen binding in muscle.

Cytochromes

Heme-containing proteins support electron transfer.

Slide 44 · Porphyria may be inherited or acquired

Inherited metabolic disturbance

An inborn disturbance of porphyrin metabolism

Part of the porphyria spectrum

Acquired metabolic disturbance

A disturbance arising without a primary inherited defect

Also within the porphyria spectrum

Slide 45 · Classification is clinical and biochemical

Robbins explicitly uses both clinical and biochemical features to classify porphyrias.

The named categories are not defined solely by skin histology.

Cutaneous blistering is one disease manifestation; The biochemical phenotype remains central.

Slide 46 · Five major porphyria groups

These are the textbook categories, not an independently updated taxonomy.

Textbook category

Teaching distinction

Congenital erythropoietic porphyria

One of the five groups identified in the text

Erythrohepatic protoporphyria

Textbook terminology retained as printed

Acute intermittent porphyria

Included in classification; Skin findings are not asserted for every case

Porphyria cutanea tarda

Cutaneous name within the classified group

Mixed porphyria

Classification category in the source

Slide 47 · Sunlight is a key cutaneous exacerbating factor

The detailed mechanism of the described microscopic alterations is uncertain.

Porphyrin-metabolism disturbance

Exposure to sunlight

Exacerbation of cutaneous lesions

Urticaria, vesicles, or scarring may be observed

Slide 48 · Clinical cutaneous manifestations of porphyria

Urticarial lesions may occur.

Vesicles are a characteristic cutaneous manifestation in the chapter.

Scarring can accompany the lesions.

Sun exposure exacerbates these manifestations.

Slide 49 · Clinical blister and scar are different observations

Active lesion

Vesicle or bulla

Focal fluid-filled separation

A temporal indicator of ongoing injury

Healed lesion

Scarring may persist

Evidence of preceding injury

Neither appearance alone identifies the metabolic subgroup

Slide 50 · Porphyria blisters are subepidermal

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

Robbins locates the vesicles beneath the epidermis.

The separation plane is shared by multiple bullous diseases.

Associated dermal vascular alterations help interpret this pattern.

Slide 51 · A distinct dermal vascular feature

Dermal vessels adjacent to porphyric blisters have thickened walls.

The thickening has a glassy or hyaline appearance.

This associated finding adds diagnostic context beyond the blister plane.

Slide 52 · What accumulates in thickened vessel walls?

A vascular-wall deposit should not automatically be interpreted as pathogenic autoantibody targeting.

Adjacent dermal vessels

Glassy wall-thickening material

Serum proteins are deposited

Immunoglobulins are among the constituents

Slide 53 · Mechanistic uncertainty must be retained

The pathogenesis of the described porphyria skin alterations is not understood.

Sunlight exacerbation is an observation, not a fully specified molecular sequence in this source.

Do not infer a defined antibody-mediated blister mechanism solely from vascular immunoglobulin deposits.

Slide 54 · Pattern recognition: Porphyria-associated bulla

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

Subepidermal blister is the principal separation pattern.

Dermal papillae at the base may appear relatively rigid.

Adjacent vessel walls are thickened by glassy proteinaceous material.

Slide 55 · EB versus porphyria: Principal distinctions

Feature

Epidermolysis bullosa

Porphyria

Primary mechanism

Inherited structural-protein defect

Porphyrin-metabolism disturbance

Typical provocation

Friction, pressure, trauma

Sunlight exacerbation

Age / timing

At or soon after birth (typical)

Not specified as one pattern

Histologic emphasis

Precise cleavage level

Subepidermal blister; Glassy dermal vessel walls

Slide 56 · Contrast with autoimmune blistering disease

Entity

Mechanism

Typical plane / clue

Pemphigus

Anti-desmoglein IgG; Acantholysis

Subcorneal or suprabasal

Bullous pemphigoid

Anti-BPAG; Inflammatory injury

Subepidermal; Eosinophils; Linear complement

Dermatitis herpetiformis

IgA-associated injury

Subepidermal; Papillary neutrophils / granular IgA

EB

Inherited structural defect

Basal, lamina lucida, or deeper

Porphyria

Metabolic disturbance

Subepidermal; Hyaline dermal vessels

Slide 57 · Bullous pemphigoid: Key differential features

Related Robbins section, pp. 1055–1056.

Bullous pemphigoid is an autoimmune disease of epidermal attachment.

Its subepidermal blisters can contain eosinophils and other inflammatory cells.

Linear basement-membrane complement deposition is.

BPAG2 links its target biology to genetic junctional EB.

Slide 58 · Dermatitis herpetiformis: Contrasting pattern

Related Robbins section, p. 1055.

Characteristically presents with grouped, intensely pruritic vesicles.

Neutrophilic microabscesses occur at tips of dermal papillae.

Direct immunofluorescence shows granular IgA at papillary tips.

It shares a subepidermal plane but not the same etiology as EB or porphyria.

Slide 59 · A shared cleavage plane does not imply shared cause

Upper epidermis

Basal keratinocytes

Lamina lucida

Lamina densa

Anchoring fibrils / dermis

Simplified anatomical schematic

Subepidermal blisters arise in junctional EB, porphyria, and immune-mediated bullous disease.

Identify the exact compartment and associated tissue reaction.

Timing, exposure, inflammation, and protein/genetic context supply discrimination.

Slide 60 · Case: Sunlight-associated vesicles

Constructed teaching vignette

A person develops sun-exacerbated cutaneous vesicles. A biopsy shows a subepidermal split and glassy thickening of dermal vessels.

Which disease group is favored by the combination?

Interpretation

Porphyria-associated cutaneous disease

Sunlight provocation plus glassy vessel walls is characteristic of the source description.

Slide 61 · Case: Subepidermal blister is nonspecific

Constructed teaching vignette

A pathology report states only “subepidermal blister.” No exposure history or tissue-reaction details are given.

Is junctional EB established by the reported plane?

Interpretation

No; The information is insufficient.

Porphyria, pemphigoid, and dermatitis herpetiformis may also split below the epidermis.

Slide 62 · Common diagnostic reasoning errors

Equating every subepidermal blister with one diagnosis ignores divergent etiologies.

Assuming immunoglobulin-containing vascular deposits establish bullous pemphigoid is unjustified.

Calling all EB autosomal recessive overlooks common dominant simplex and variable dystrophic forms.

Assigning a complete molecular mechanism to porphyria skin injury exceeds the cited text.

Slide 63 · Integrating a blistering-disorder differential

Precise localization and causal reasoning are complementary, not interchangeable.

Start with onset and trigger

Localize cleavage plane

Examine inflammation and dermal changes

Interpret against structural, autoimmune, or metabolic mechanisms

Slide 64 · EB: Three associations to retain

Basal epidermis

KRT5 / KRT14 — EB simplex

Lamina lucida

Laminin; Sometimes BPAG2 — junctional EB

Below lamina densa

COL7A1 / collagen VII — dystrophic EB

Slide 65 · Porphyria: Three associations to retain

Clinical

Sun-exacerbated urticaria, vesicles, and scarring

Histology

Subepidermal blister

Dermis

Glassy thickening of vessel walls with serum proteins

Slide 66 · Reference and interpretation

Core reference

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th ed. 2026. Chapter 25, The Skin; noninflammatory blistering disorders, pp. 1055–1058.

Adjacent Robbins sections on pemphigus, bullous pemphigoid, and dermatitis herpetiformis provide the differential context.

Original source figures 25.27, 25.28, 25.34, and 25.35 informed the compartmental descriptions; no textbook figure images have been reproduced.