Hereditary Spherocytosis

Slide 1 · Hereditary Spherocytosis

Red cell membrane skeleton, splenic hemolysis and clinical expression

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Explain how membrane-skeleton proteins maintain red cell deformability.

Trace membrane loss to spherocyte formation and splenic destruction.

Connect the laboratory findings with the underlying mechanisms.

Interpret clinical severity, crises, and the effect of splenectomy.

Slide 3 · Definition and core lesion

Inherited abnormality of the red cell membrane skeleton.

Progressive membrane loss converts red cells from disks toward spheres.

Reduced deformability predisposes cells to splenic sequestration.

Premature removal by macrophages produces extravascular hemolysis.

The primary defect is intrinsic to the red cell; The spleen is the chief site of destruction.

Slide 4 · Hereditary spherocytosis in one mechanism

Membrane-skeleton insufficiency

Membrane shedding

Spherocytic, rigid red cells

Splenic clearance

A structural membrane abnormality becomes a clinical hemolytic anemia.

Slide 5 · Hemolysis: Essential parent context

Extravascular hemolysis

Premature removal within phagocytes

Often linked to impaired red cell deformability

Can produce splenomegaly and jaundice

Intravascular hemolysis

Red cell rupture within the circulation

Can produce hemoglobinemia and hemoglobinuria

Mechanistically distinct from typical HS

Hereditary spherocytosis is a model of extravascular hemolysis.

Slide 6 · Geographic occurrence

Hereditary spherocytosis occurs worldwide.

The supplied Robbins text reports its highest prevalence in northern Europe.

The reported northern European prevalence is approximately 1 in 5,000.

Prevalence and inheritance are context, not standalone diagnostic tests.

Slide 7 · Inheritance patterns

Approximately 75% of cases show an autosomal dominant pattern.

Other patients may have a more severe phenotype associated with two different defects.

Inheritance of two different deleterious alleles is termed compound heterozygosity.

Family history supports suspicion, but clinical severity varies.

Slide 8 · Why two defective alleles can produce severe disease

Two different defects

Greater loss of membrane proteins

More impaired skeleton assembly

More severe hemolysis

Compound heterozygosity with deeper structural deficiency and, generally, greater severity.

Slide 9 · The normal red cell must be deformable

The biconcave red cell can change shape in narrow microvascular passages.

Its specialized membrane skeleton supplies flexibility and durability.

The skeleton lies directly beneath the plasma membrane.

The spleen makes exceptional demands on red cell deformability.

Membrane mechanics are central to red cell survival.

Slide 10 · Normal red cell: Two coupled layers

Lipid bilayer

Submembranous protein lattice

Native schematic: The membrane and skeletal meshwork function as a coupled mechanical system.

Schematic — not to molecular scale

Slide 11 · Spectrin: The principal scaffold

Spectrin is the chief structural protein of the red cell skeleton.

Its α- and β-polypeptide chains form flexible helical heterodimers.

Spectrin dimers connect to other units to form a resilient mesh.

Defects that diminish spectrin compromise the skeleton as a whole.

Slide 12 · From spectrin dimer to tetramer

α-spectrin + β-spectrin

Flexible heterodimer

Dimer head-to-head association

Spectrin tetramer

The association of spectrin units permits an extended network beneath the membrane.

Slide 13 · How the spectrin–actin network forms

Spectrin tetramers

Tail attachment to actin

Multiple tetramers per actin oligomer

Two-dimensional lattice

The network can stretch and recoil while the red cell deforms.

Slide 14 · Two attachment systems connect skeleton to bilayer

Membrane tether: Ankyrin pathway

Membrane tether: Protein 4.1 pathway

Band 3 (transmembrane)

Ankyrin + band 4.2

Spectrin

Glycophorin A (membrane)

Protein 4.1

Spectrin / actin junction

Two specific anchoring relationships stabilize the overlying bilayer.

Slide 15 · Ankyrin–band 3 anchoring pathway

Band 3 is a transmembrane ion transporter.

Ankyrin and band 4.2 connect spectrin to band 3.

This interaction tethers the skeleton to the lipid bilayer.

Mutations disrupting this route favor membrane instability.

Slide 16 · Protein 4.1–glycophorin pathway

Protein 4.1 contributes a second membrane-skeleton connection.

It couples the tail region of spectrin to glycophorin A.

This connection acts alongside ankyrin–band 3 tethering.

A mechanically integrated bilayer and skeleton are required for normal red cells.

Slide 17 · Principal proteins implicated in HS

Protein

Normal role

Pathogenic consequence

Ankyrin

Linker in band 3 tether

Weakened membrane attachment

Band 3

Transmembrane anchor / transporter

Impaired bilayer–skeleton coupling

Spectrin (α or β)

Flexible cytoskeletal scaffold

Defective skeletal lattice

Band 4.2

Stabilizes ankyrin–band 3 complex

Less stable skeleton anchorage

Protein functions and mutation targets are drawn; This is not a complete genetic variant catalogue.

Slide 18 · A common genetic consequence: Missing protein

Many HS mutations as frameshifts or premature stop codons.

A mutant allele may fail to make the corresponding protein.

Insufficiency of one component limits assembly of the wider skeleton.

The membrane then becomes vulnerable to loss during circulation.

Slide 19 · Gene defect to cytoskeletal insufficiency

Protein-altering mutation

Less membrane-skeletal protein

Poorly assembled lattice

Unstable lipid bilayer

The effect is not confined to one protein; Insufficiency can destabilize the integrated network.

Slide 20 · Why young HS red cells may look normal

Young hereditary spherocytosis red cells may retain normal shape.

Membrane instability is expressed progressively as red cells circulate.

Repeated passage and aging allow cumulative loss of membrane fragments.

Spherocytes thus represent the evolving consequence of a structural defect.

Slide 21 · Progressive membrane shedding

Young affected red cell

Weak bilayer anchorage

Membrane fragments lost with age

Reduced cell surface area

Progressive membrane loss, rather than initial red cell production as a sphere, explains the characteristic shape.

Slide 22 · A disk becomes a sphere

Normal biconcave erythrocyte

Relatively large surface area for its volume; Central pallor in a planar view.

Spherocytic erythrocyte

Reduced membrane area relative to contents; Dense, round appearance.

Schematic — not a photomicrograph

Original diagram based on the described shape change; Not a clinical smear.

Slide 23 · Geometry: Falling surface-area-to-volume ratio

Membrane vesiculation decreases surface area relative to cell contents.

The cell becomes progressively less able to retain a biconcave outline.

A sphere uses the least surface area for a given volume.

Shape change is the visible expression of lost membrane.

Slide 24 · Why a spherocyte has poor deformability

Surface area lost

Spherical geometry

Lower shape reserve

Difficulty traversing splenic slits

Spherocytes cannot make the extreme contour changes demanded by splenic circulation.

Slide 25 · The potassium-and-water contribution

Splenic exposure can intensify membrane loss from HS red cells.

Affected red cells may lose K⁺ ions and H₂O.

Cellular dehydration contributes to increased mean cell hemoglobin concentration.

The result compounds impaired cell geometry and splenic retention.

Slide 26 · Complete pathogenic chain

Defective tether

Vesiculation

Spherocytosis

Reduced flexibility

Splenic removal

A single pathway connects gene-level lesions with anemia, splenomegaly and jaundice.

Slide 27 · Why the spleen is the decisive organ

Normal erythrocytes traverse the splenic red-pulp cords to reach venous sinusoids.

This transition requires pronounced mechanical deformation.

Spherocytes are poorly suited to that passage.

Retention creates prolonged contact with resident phagocytes.

Slide 28 · Splenic red-pulp filtration

Splenic red-pulp cords

Sinusoid

Trapped

Spherocytes

Less deformable spherocytes accumulate in cords; More deformable cells can pass to sinusoids.

Slide 29 · From mechanical retention to destruction

Rigid spherocyte in cord

Prolonged residence

Macrophage recognition

Phagocytosis

Splenic destruction is predominantly extravascular; It need not involve red cell rupture in plasma.

Slide 30 · Local splenic conditions worsen red cell injury

Prolonged erythrostasis exposes spherocytes to metabolically demanding conditions.

Glucose depletion and reduced pH as proposed contributors.

Membrane loss and loss of K⁺ and H₂O may intensify during sequestration.

These influences amplify the underlying membrane-skeleton lesion.

Slide 31 · Splenectomy reveals the mechanism

Removal of the spleen markedly reduces premature red cell removal.

Anemia can be corrected even though the inherited membrane lesion remains.

Spherocytes therefore persist after splenectomy.

The intervention separates cell shape from the organ-specific site of clearance.

A hematologic response to splenectomy does not mean the genetic membrane defect has disappeared.

Slide 32 · Red cell survival is markedly shortened

Red cell lifespan in days

Normal red cell

120 days

HS red cell

10–20

Robbins gives an average affected-cell lifespan of 10–20 days, compared with about 120 days normally.

Slide 33 · Compensatory erythropoiesis

Accelerated erythrocyte loss

Lower oxygen delivery

Renal erythropoietin response

Increased marrow red cell output

Marrow compensation can be sufficient in mild HS or inadequate when hemolysis is greater.

Slide 34 · Bone marrow response

Enhanced erythropoietin drive stimulates erythroid precursors in the marrow.

Erythroid hyperplasia is a general consequence of sustained hemolytic anemia.

An expanded erythroid compartment attempts to replace prematurely lost cells.

The magnitude of marrow compensation influences clinical severity.

Slide 35 · Reticulocytosis: The blood counterpart of compensation

Increased marrow output releases more reticulocytes into the circulation.

Reticulocytes are larger, RNA-containing recently released red cells.

Peripheral reticulocytosis reflects an active erythropoietic response.

An abrupt loss of reticulocyte production is central to an aplastic crisis.

Slide 36 · Peripheral morphology: Identify the pattern

Red cell with central pallor

Biconcavity gives a pale center in the conceptual planar projection.

Spherocyte

Round, compact red cell lacking the typical central pallor.

Schematic — not a photomicrograph

Schematic — genuine blood film not available in the provided source files.

Slide 37 · What morphology establishes—and what it does not

A spherocytic shape supports a red cell membrane or clearance abnormality.

Morphology should be interpreted with the clinical and inherited pattern.

The underlying membrane protein defect cannot be identified from shape alone.

Diagnostic testing must be integrated rather than inferred from an isolated cell.

Slide 38 · Raised mean cell hemoglobin concentration

An increased mean cell hemoglobin concentration in HS.

The change reflects dehydration as red cells lose K⁺ and H₂O.

Membrane loss is the cause of spherocytic geometry; Dehydration modifies cell concentration.

A blood-count index is supportive rather than molecularly specific.

Slide 39 · Mechanism of increased MCHC

Splenic membrane injury

K⁺ and H₂O loss

Red cell dehydration

Raised MCHC

MCHC = mean cell hemoglobin concentration; It is not synonymous with total hemoglobin concentration.

Slide 40 · Eosin-5-maleimide test: Basic principle

Eosin-5-maleimide (EMA) is a fluorescent dye used in confirmatory testing.

It binds selectively to the band 3 membrane protein.

Disorders such as HS with reduced membrane material show decreased fluorescence.

The signal is an indicator of membrane abnormality, not direct allele sequencing.

Slide 41 · EMA binding assay: Interpretation

Incubate red cells with EMA

Dye binds band 3

Measure fluorescence

Reduced binding supports membrane loss

EMA fluorescence as a useful confirmatory test; Interpretation requires clinical context.

Slide 42 · Pathology-centered diagnostic reasoning

Hemolytic phenotype

Spherocytic red cells

Raised MCHC / reticulocytosis

Decreased EMA fluorescence

Concordance between mechanism, morphology and laboratory findings is more informative than any one feature.

Slide 43 · The characteristic clinical triad

Anemia: Red cell destruction outstrips replacement.

Splenomegaly: Sustained red cell sequestration and macrophage activity.

Jaundice: Increased bilirubin generation during heme catabolism.

The degree of each finding varies considerably among affected patients.

Anemia + splenomegaly + jaundice reflects the physiology of extravascular hemolysis.

Slide 44 · Why anemia develops

Premature splenic RBC clearance

Decreased circulating cell survival

Erythropoietic compensation

Residual hemoglobin deficit

Clinical anemia emerges when compensatory production cannot keep pace with red cell loss.

Slide 45 · Why the spleen enlarges

Chronic sequestration

Macrophage phagocytosis

Phagocyte expansion

Splenomegaly

Splenic enlargement is a pathologic consequence of sustained extravascular destruction.

Slide 46 · Why jaundice develops

Hemoglobin from cleared RBCs

Heme degradation

Unconjugated bilirubin production

Jaundice

The parent hemolytic-anemia section specifies unconjugated hyperbilirubinemia in uncomplicated hemolysis.

Slide 47 · From chronic hemolysis to pigment stones

Increased heme turnover

Increased bilirubin production

Greater biliary bilirubin excretion

Pigment gallstone formation

Cholelithiasis can produce an additional symptomatic burden independent of the anemia.

Slide 48 · Mild or compensated disease

In approximately 20%–30%, increased erythropoiesis fully compensates for reduced survival.

These patients may have few symptoms or remain nearly asymptomatic.

A minimal hemoglobin deficit does not imply normal red cell survival.

Clinical findings reflect the balance between destruction and production.

Slide 49 · Typical chronic disease

For most affected patients, compensation does not entirely match hemolysis.

The resulting anemia is usually mild to moderate and chronic.

Splenomegaly and jaundice reflect continuous extravascular clearance.

A relatively stable baseline may still be disrupted by acute events.

Slide 50 · Severe disease in the newborn

A small minority present at birth with marked jaundice.

Severe neonatal presentation is especially associated with compound heterozygosity.

Exchange transfusion may be necessary.

Early presentation reflects high hemolytic burden relative to compensation.

Slide 51 · Aplastic crisis: The interruption of supply

Acute parvovirus infection

Loss of erythroid progenitors

Temporary cessation of RBC production

Sudden worsening of anemia

Because red cell survival is already short, even brief suppression of replacement is consequential.

Slide 52 · Parvovirus-associated marrow suppression

Parvovirus can infect and kill erythroid progenitors.

During the infection, new red cell production may temporarily cease.

Recovery after immune clearance, generally within 1–2 weeks.

Transfusion support may be required during the acute period.

Slide 53 · Why a short production pause is dangerous

HS RBCs survive 10–20 days

Marrow replacement abruptly stops

Remaining RBCs continue to be cleared

Hemoglobin falls rapidly

An aplastic crisis is a failure of production superimposed on accelerated clearance.

Slide 54 · Hemolytic crisis: Accelerated clearance

A hemolytic crisis reflects a transient increase in red cell destruction.

Robbins gives infectious mononucleosis with increased spleen size as an example.

The underlying membrane lesion is unchanged during the intercurrent event.

, hemolytic crises are generally less significant than aplastic crises.

Slide 55 · Aplastic crisis versus hemolytic crisis

Feature

Aplastic crisis

Hemolytic crisis

Dominant process

Red cell production falls

Splenic red cell destruction rises

Example trigger

Parvovirus infection

Intercurrent infection / splenic enlargement

Immediate mechanism

Erythroid progenitor injury

Increased clearance of rigid red cells

Major risk

Rapid anemia worsening as cells age out

Additional hemolytic anemia

Robbins emphasis

Potential need for transfusion

Usually less consequential

Slide 56 · Clinical complications arise from distinct mechanisms

Chronic hemolysis produces anemia and bilirubin overload.

Pigment gallstones reflect sustained heme turnover.

Aplastic crisis represents interruption of erythropoiesis.

Hemolytic crisis represents increased destruction under additional splenic stress.

Slide 57 · Splenectomy: Benefit and cost

Remove dominant site of clearance

Prolong RBC survival

Correct anemia

Increase susceptibility to sepsis

The spleen is an important filter of blood-borne bacteria.

Slide 58 · Before and after splenectomy

Before splenectomy

Splenic sequestration is prominent

Spherocytes have shortened survival

Hemolytic anemia may persist

After splenectomy

Spherocytes still circulate

Red cell loss is diminished

Anemia improves; Sepsis risk rises

Splenectomy treats the consequence of membrane pathology, not the inherited molecular cause.

Slide 59 · Why sepsis risk matters after splenectomy

The spleen normally filters blood-borne microorganisms.

Its removal reduces an important host-defense mechanism.

The resulting increased risk of serious infection must be weighed against anemia control.

The Robbins passage does not supply a regimen for prophylaxis or vaccination.

Slide 60 · Case: Chronic anemia with splenomegaly

Clinical vignette

A patient has a long-standing hemolytic anemia, jaundice and an enlarged spleen. The peripheral blood includes numerous small, densely stained round erythrocytes.

Teaching question

How does a membrane-skeleton defect produce the clinical triad?

Answer: Membrane shedding → spherocytes → splenic phagocytosis → anemia, splenomegaly and bilirubin excess.

Slide 61 · Case: Sudden worsening after viral illness

Clinical vignette

A patient with stable hereditary spherocytosis develops a pronounced fall in hemoglobin during an acute illness, with markedly reduced erythroid output.

Teaching question

Which mechanism best explains this abrupt deterioration?

Answer: Transient suppression of red cell production—consider a parvovirus-associated aplastic crisis.

Slide 62 · Case: Anemia improves, spherocytes remain

Clinical vignette

A person with hereditary spherocytosis undergoes splenectomy. The anemia improves, but spherocytes are still seen on the blood film.

Teaching question

Does persistent spherocytosis mean splenectomy failed?

Answer: No. The spleen was removed as a site of clearance; The intrinsic membrane lesion persists.

Slide 63 · Conceptual differential: Site of hemolysis

Observation

Typical HS (extravascular)

Intravascular hemolysis

Dominant process

Macrophage removal of intact RBCs

Red cell disruption in circulation

Anatomic emphasis

Splenic red pulp

Blood plasma / vasculature

Splenomegaly

Expected in many patients

Not typical per Robbins

Urinary hemoglobin

Not a defining feature

Can be present

Shared biology

Accelerated heme degradation

Accelerated heme degradation

This contrast is restricted to the general hemolytic-anemia framework.

Slide 64 · Important interpretive distinctions

Membrane skeleton insufficiency is the primary lesion; Hemolysis is its consequence.

Spherocytes can remain after splenectomy because the shape defect persists.

Elevated MCHC relates to dehydration; Reduced surface area explains spherical shape.

Aplastic and hemolytic crises differ in production versus destruction.

Slide 65 · Mechanism consolidated

Inherited protein deficiency

Loss of membrane area

Spherocytes

Splenic extravascular hemolysis

Clinical triad

Genotype → membrane mechanics → cellular geometry → organ-level clearance → clinical phenotype.

Slide 66 · Clinical synthesis

Severity depends on whether marrow compensation keeps pace with shortened cell survival.

Chronic bilirubin excess may lead to symptomatic pigment gallstones.

Parvovirus-mediated cessation of production explains severe aplastic crises.

Splenectomy improves anemia but increases infection susceptibility.

Slide 67 · References and source boundaries

Primary source

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th edition (2026). Chapter 14: Red Blood Cell and Bleeding Disorders, pp. 579–581.

Source scope

Hereditary Spherocytosis, with limited parent-section context from Hemolytic Anemias. All mechanism diagrams and cell drawings are original editable schematics.

No genuine blood-smear image or textbook figure is reproduced in this deck.