Cells can accumulate pigments or other substances as a result of a variety
of different pathological and physiological processes- and this is usually
an early indicator of cell stress or reversible injury
Substances that may be accumulated:
 normal cell constituents-which accumulate in an excess (lipids, proteins,
 abnormal substances, as a product of abnormal metabolism
 pigments=colored substances
These substances can accumulate transiently or permanently, they may be
harmless to the cells or toxic
can be located-in nuclei
-in cytoplasm, most frequently within lysosomes
The processes resulting in an abnormal accumulation of substances in the
cells can be many, but there are three general types
1.-abnormal metabolism of normal endogenous substance- normal
endogenous substance is produced at a normal or increased rate, and the
rate of metabolism is inadequate to remove it
example- fatty change of the liver
2.-normal or abnormal substance accumulates because it cannot
be metabolized- due to lack of enzymes that blocks the specific
metabolic pathways
example- lysosomal storage diseases - broad group of inherited disorders,
such as various forms of glycogenoses (in which glycogen is stored within
the cytoplasm of various cells) or lysosomal storage diseases with
accumulation of complex substances, such as mucopolysaccharides
3.-deposition of abnormal exogenous substance-is deposited
because the cell can neither metabolize it nor has the ability to trasport
it out of the cell
example-accumulation of carbon particles in the lungs and in lymph nodes,
or silica particles in lungs
Intracellular accumulations of substances can be
-reversible (overload is due to increased rate of metabolism, that
can be brought under control)
-irreversible - for example storage disease due to genetic disorder
- accumulation may be progressive and cause secondary injury or cell
Fatty change (steatosis)
-represents any abnormal accumulation of fat within the cells.
-is usually an early indicator of cell injury, fatty change itself
represent nonlethal injury, but may also be seen in dead cells or is
encountered in cells adjacent to necrosis
-fatty change is often seen in liver, but it can also occur in heart,
muscle, kidney etc.
Light microscopy:
 fat vacuoles (clear, optically empty) within the cytoplasm
 Positive identification of fat in routine sections (paraffin embedded
tissue sections) is not possible because of a use of fat solvents during
tissue-embedding procedure, but it is possible to prepare frozen
section of normal fresh tissues. These sections can be stained for
example by Sudan Black or Oil-red-O to demonstrate presence of fat.
fatty change occurs occassionally almost in all organs, but it is most
common in the liver-because it has a central role in fat metabolism
 causes of fatty liver
-excessive alcohol consumption is a common cause, protein
malnutrition, diabetes mellitus, obesity, hepatotoxins, and drugs
 gross appearance:
mild fatty change does not affect the gross appearance
more severe fatty change- the liver is enlarged, and yellow and greasy, it
has an increased weight (even more than 3 to 5 kg)- hepatomegaly
 light microscopy:
small fat vacuoles in the cytoplasm, first only around the nucleus, later
multiple vacuoles coalesce and may create large clear spaces - nuclei are
displaced to the periphery of the cell
 pathogenesis of fatty liver
-excessive accumulation of triglycerides within the liver cell may be
caused by:
a-excessive entry of free acids to liver cell
-if there is an excessive amount of fat-rich diet
-on the other hand, also in starvation-adipose tissue fat is mobilized,
more fatty acids enter liver cell and concurently there is less apoprotein
due to decreased proteosynthesis
b-impaired or decreased fatty acid metabolism
-effect of alcohol poisoning, also in chronic hypoxia
c-decreased apoprotein synthesis
-protein malnutrition from various causes
different types of disturbances may cause fatty change of liver
most common= alcohol liver disease
other causes -protein malnutrition, diabetes mellitus, obesity,
hepatotoxins, various chronic diseases
 Significance of fatty change in liver
-depends on the cause and the severity of accumulation
mild fatty change-has no effect on the function
more severe fatty change - cell injury or cell death
-for example the liver in alcoholic disease becomes progressively
fatty, enlarged, and accumulation of fat finally leads to liver fibrosis
(increase in amount of connective tissue) and liver cirrhosis (structural
change of the liver associated with increased amount of fibrous tissue
and progressive liver dysfunction)
-lipids are frequently found in heart muscle in the form of small
two patterns:
1-in prolonged mild hypoxia—„tigered effect“
-here intracellular deposits of fat create grossly apparent yellow bands
alternating with bands of red-brownish colour of uninvolved myocardium
(in anaemia)
2- in more profound hypoxia or in severe types of myocarditisfatty change is diffuse -injured or dead cells (diphteria)
macrophages accumulating lipids (triglycerids, cholesterol and
cholesterol esters), are encountered in a variety of diseases, such as
atherosclerosis - the lipids accumulate in the smooth muscle cells
and macrophages of intimal layer of the aorta and of large arteries these phagocytic cells may become overloaded with lipids - foamy cells.
These lipid-rich cells may rupture and release the lipids into the ground
substance of the intima- these extracellular lipids and mainly cholesterol
may crystalize and appear as needle-shaped clefts at light microscopy
xanthoma- tumorous masses composed of foamy cells -in
subepithelial connective tissue of the skin and near tendons
(in hereditary or acquired hyperlipidemia)
foamy macrophages-may also occur near necrotic foci or adjacent
to inflammation- due to phagocytosis of lipid substances derived from
injured cells
stromal infiltration of fat-common in connective tissue of heart
muscle, in pancreas, parotid gland- only rarely affects to function of the
accumulation of proteins within the cell can be observed for example
-in proteinuria -protein-loss in the urine - occurs in epithelial cells
of proximal tubules
-no protein should normally appear in the urine, if glomerular
membrane is injured - occurs proteinuria - the proteins are phagocytized
by the tubular cells by the process called pinocytosis -protein-rich
droplets (pink, hyaline) in the cytoplasm of epithelial cell of renal
proximal tubuli
-plasma cells - synthesis of immnoglobulins
in chronic inflammatory reactions, the plasma cells may be overloaded
with their synthetic products (IgG)- results in formation of large
homogenous eosinophilic inclusions-Russel bodies- huge dilatation of
cisternae of ER, where proteosynthesis occurs
-excessive intracellular accumulation of glycogen -in patients with
glucose or glycogen metabolism disorders
1-Diabetes mellitus -is the most common and most important
disorder of glucose metabolism
Glycogen is found in epithelial cells of distal portions of proximal tubules
and Henle loops= Armani cells
= glycogen storage diseases- group of diseases characterized by
excessive accumulation of glycogen either normal or abnormal due to
inherited deficiency of any of the enzymes involved in glycogen synthesis
or degradation
-there are several subgroups of glycogenoses, depending on a
specific enzyme deficiency- distribution of glycogen varies between
different types of glycogenoses
1) hepatic types of glycogenoses - caused by deficiency of hepatic
enzymes involved in glycogen metabolism, such as lack of glucose-6phosphatase
= VON GIERKE disease ( type I glycogenosis)
clinical effects:
enlargment of liver- due to storage of glycogen in hepatocytes
hypoglycemia due to failure of glucose production
enlargment of kidney
bleeding tendency due to platelet dysfunction
mortality about 50 percent
2) myopathic type - in striated muscles - glycogen is an important
source of energy
lack of enzymes such as muscle phosphorylase cause block of
glycogenolysis, that induces accumulation of glycogen in skeletal muscles
= Mc Ardler syndrome ( type V glycogenosis )
clinical effects:
painful cramps in skeletal muscles during exercise
3) generalized glycogenosis - deficiency of lysosomal enzyme
involved in glycogen metabolism ( acid maltase )
resulting in accumulation of glycogen in virtually all organs
most important in heart muscle, liver, skeletal muscle = POMPE DISEASE
( type II glycogenosis )
clinical effects:
massive cardiomegaly- heart failure within 2-3 years
mild hepatomegaly
- accumulation of lipid-carbohydrate susbtances within the cells
typically occurs in lysosomal storage diseases
- inheredited usually autosomal recessive errors of metabolism in
which there is lack of a specific lysosomal enzyme involved in breakdown
of complex substrates, such as mucopolysaccharides or sphingolipids
resulting in storage (accumulation) of various insoluble intermediate
metabolites within the cells of mononuclear phagocyte system
-abnormal substances are phagocytosed in RES cells - they change
to foamy cells= macrophages of extreme size with pale foamy cytoplasm
-most foamy macrophages - in the spleen, liver, bone marrow, lymph
nodes, etc. hepatosplenomegaly
there are numerous lysosomal storage diseases- they can be
divided into categories according to biochemical nature of substances and
metabolites that are accumulated
deficient activity of the enzyme glucocerebrosidase that normally cleaves
glucose from ceramide- this leads to an accumulation of
glucocerebrosides in Gaucher’s cells (foamy macrophages)
clinical effects:
-it is characterized by hepatosplenomegaly - spleen is massively
enlarged- hypersplenism may contribute to anemia and leukopenia
-Gaucher’s cells occur especially in bone marrow, liver, spleen,
lymph nodes etc.- because glycolipids are derived from the breakdown of
blood cells (particularly RBCs) change to glucocerebrosides- transit
through the blood- are engulfed by macrophages
-this disorder is severe, ofetn can be lethal
current therapy: enzyme replacement by infusion of purified
lysosomal accumulation of sfingomyelin and cholesterol, defect of enzyme
-the phagocytic cells are filled with particles and droplets of
complex lipid
-most severely affected organs are spleen, liver, bone marrow,
lymph nodes, lungs, neurons.
Clinical significance:
-manifests in infancy- sever neurologic detererioration and
visceromegaly-lethal usually within 2-3 years of life
therapy: unknown, antenatal diagnosis is possible by the use of
amniocenthesis ( examination of amniotic fluid- fibroblasts accumulate )
 3) TAY-SACHS DISEASES ( gangliosidosis)
gangliosidoses are characterized by accumulation of gangliosides due to
deficiency of lysosomal enzyme, most commonly hexosaminidase A
-the brain is principally affected- storage of gangliosides within
neurons and glial cells
-affected cells are foamy, enlarged, swollen
-retina is usually involved
infants suffer of mental retardation, blindness, neurologic disorders,
which leads to certain death within 2-3 years
mucopolysaccharides in different tissues
-m. that accumulate include dermatan sulfate, heparan sulfate,
keratan sulfate
MPS- is progressive disorder characterized by involvement of multiple
organs including liver, spleen, blood vessels, heart,
clinically: most are associated with severe skeletal abnormalities, mental
affected children die within 8-10 years
they develop severe coarse facial features with skeletal abnormalities =
death due to heart failure
Pigments are coloured substances which represent either normal
constituents of the cell, such as melanin- or abnormal substances
deposited only under special circumstances
pigments can be
-exogenous (coming from outside the body)
-endogenous (synthesized within the body itself)
 exogenous - the most common are carbone particles or coal dust, which
is virtually ubiquitous air pollutant, when inhaled-picked up by
macrophages within the alveoli and lymph nodes of tracheobronchial
anthracosis- accumulation of carbon particles in the lungs
aggregates of carbone particles causes fibroblastic reaction in the lungsthat causes chronic emphysema - serious lung disease termed
- tatooing- injected pigment is taken up by macrophages and
persists forever in the cells and extracellularly- in dermal macrophages
and fibroblasts
 endogenous- include -lipofuscin, melanin, hemoblobin-derived pigments,
such as hemosiderin, bilirubin, etc.
insoluble pigment- fine intracytoplasmic granules, yellow-brown
called aging pigment- because it is seen mainly in the cells that are
undergoing slow regressive changes. Lipofuscin is composed of complex
lipids, it is derived of peroxidation of lipids, mostly from cellular
membranes in cell injury
- lipofuscin is often associated with atrophy- brown atrophy
- prominent accumulation of lipofuscin in liver and heart of aging patients,
or in patients with severe malnutrition, for example in cancer cachexia
(usually accompanied by shrinkage of the entire organ)
on electron microscopy:
lipofuscin represents indigestible residues of autophagic vacuoles.
Lipofuscin itself is not injurious to the cell.
is an endogenous non-hemoglobin-derived pigment, brown-black in color,
produced in melanocytes
- melanin is derived from tyrosine, the pigment is formed when enzyme
tyrosinase catalyzes the oxidation of tyrosine to dihydroxyphenylalanin in
melanocytes in the structures called melanosomes-melanin is distributed
to the other epidermal cells-the function of melanin is to block harmful UV rays from the
epidermal nuclei
-melanin may accumulate in excessive quantities in benign and
malignant melanocytic lesions- nevi, melanoma
-in inflammatory skin lesions- melanin may be released from injured
basal cells and taken up by dermal macrophages- this give rise to postinflammatory pigmentation of the skin
- is a golden-yellow to brown granular pigment found in lysosomes within
the cell cytoplasm
- hemoglobin-derived pigment- it is composed of aggregates of
partially degraded ferritin
Iron metabolism is normally regulated so that the total amount of iron in
the body is maintained within relatively narrow range-the body has no effective mechanism for elimination of excess iron
-excess of iron then accumulates in macrophages and parenchymal cell in
the form of hemosiderin
- deposition of hemosiderin in tissue macrophages is termed
1) Localized hemosiderosis
-is common and results from gross hemorrhages, ruptures of small
vessels or from severe vascular congestion, etc.
-hemoglobin is broken down and its iron is deposited locally as
-no clinical significance, its presence only indicates a site of
changes in colour occurring in subcutaneous hemorrhage:
-the tissue affected by hemorrhage is first red-blue (due to lysis of
-then becomes green-blue (due to formation of biliverdin and bilirubin)
-finally it appears golden-yellow (due to transformation to hemosiderin) hemosiderin is picked up by macrophages and deposited in the tissue
2) Generalized hemosiderosis
-is less common, occurs in those conditions when there is an excess
iron in the body
-occurs following multiple tranfusions
-following excessive dietary iron
-in some hemolytic anemias
hemosiderin is deposited in many organs (liver, bone marrow, spleen,
lymph nodes) first in macrophages, later also in parenchymal cells
- it has usually no clinical significance, except of being an indication of
iron overload
 Hemochromatosis
-is uncommon inherited or idiopathic disease characterized by deposits
of hemosiderin throughout the body, the mostly affected organs are the
liver (cirrhosis), pancreas (diabetes mellitus), and the skin (brown colour)
primary defect lies in mucosal cells of the small intestine. These cells
usually absorbe only limited amount of iron from the food. In
hemochromatosis- this control is lost- and large amounts of iron are
-iron is toxic to the tissues- and leads to fibrosis and cirrhosis of
the liver
and fibrosis of pancreas with destruction of Langerhans islands- leading
to diabetes mellitus
accumulation of bilirubin is called jaundice (icterus)- yellowish
discoloration of skin and sclerae- occurs when bilirubin is elevated in the
blood and deposited in tissues
normal metabolism of bilirubin
-bilirubin is a bile pigment that represents an end product of hemoglobin
molecule destruction, it does not contain iron
-normally majority of bilirubin is formed in the cells of RES, where
erytrocytes are destroyed (spleen), minor part of bilirubin is formed in
bone marrow and liver
-then bilirubin is transported into the liver in an unconjugated form (as an
indirect bilirubin)- bound to albumin
-in the liver, bilirubin is conjugated with glucuronide to form soluble
(direct) bilirubin which is excreted by liver cells to the bile and then to
intestine- where it is changed to urobilinogen (then absorbed by portal
blood and returned to the liver or excreted in urine)
jaundice- common clinical disorder due to excess of bilirubin within cells
and tissues
Causes of jaundice -may result from three distinct mechanisms
-increased production of bilirubin
-decreased excretion by the liver
-bile duct obstruction
1) Hemolytic jaundice (increased production)
-increased destruction of erytrocytes (for example due to
hemolytic anemia) overhelms the capacity of the liver to conjugate
-leads to an accumulation of unconjugated (indirect) bilirubin in
serum-complexed to albumin, cannot be excreted in the urine-this BR is
toxic to brain- soluble in lipids
2) Hepatocellular jaundice ( decreased uptake, conjugation and excretion)
-usually both conjugated and unconjugated bilirubin levels are
urine levels of bilirubinn and urobilinogen are elevated
3) Obstructive jaundice
-biliary tract obstruction results in accumulation of bilirubin in the
liver = cholestasis
bilirubin cannot reach the intestine- this results in a failure of lipid
substances to be absorbed which causes severe clinical symptoms
including increased propensity for bleeding ( because of K-vitamin
deficiency)-hemorrhagic diathesis
Clinical effects of deposition of bilirubin
1) deposition in connective tissue (skin, scleras, internal organs) result in
yellow color typical of jaundice
2) deposition in parenchymal cells
most important -in basal ganglia (so called KERNICTERUS)
-it is uncommon condition caused by increased levels of only
unconjugated bilirubin which is lipid-soluble and can cross the blood-brain
barrier (most common in premature babies when the blood-brain
membrane is relatively permeable)
-occurs in severe neonatal anemias- most often as a result of Rh
antigen incompatibility
intracellular accumulation of bilirubin in brain is highly toxic- severe
injury or even death of neurons
Pathologic calcification implies the abnormal depositions of calcium
salts. This process is relatively common and takes one of two forms:
1. Metastatic calcification - abnormal deposition of calcium salts
in normal tissues whenever there is hypercalcemia- increased level in
serum calcium
causes of hypercalcemia include:
-vitamin D intoxication
-widespread metastatic cancer in the bones (bony metastases)- increased
bone resorption due to disseminated malignant disease- multiple myeloma,
metastatic cancer, leukemias, etc.
-h. also may results from secondary hyperparathyroidism caused by
chronic renal failure associated with a phosphate retention
Deposition od calcium:
-deposits of calcium salts occur in all normal tissues, most commonly in
arterial walls of the following organs:
- kidney- chronic renal failure due to extensive deposits of calcium salts
in the interstitium of kidney= nephrocalcinosis
- lungs- extensive involvement may rarely cause abnormalities in
diffusions of gases
-gastric mucosa- in all these sites- there are profound changes in pHcalcium salts are more stable in low pH- acidosis- less stable in higher pHalcalosis (excretion of acid metabolites)
microscopically: calcium salt deposits are basophilic (stain blue with HE),
deposits are granular, crystalic (hydroxyapatit), or in noncrystalline
amorphous form
2. Dystrophic calcification
-abnormal calcium deposits in dead, dying and injured cells and
tissues-normal serum levels of calcium and phosphates
calcification occurs in
-atheromas in advanced atherosclerosis (aorta, larger arteries)
-in aging or damaged heart valves
-in caseous necrosis (tuberculous lymph node -hard as stone),
enzymatic necrosis of fat- Balser necrosis
microscopically- the same appearance as in metastatic c.
deposits may be intra- or extracellular or both, calcification of single
necrotic cells
-progressive acquisition of salts may lead to the creation of concentric
lamellar structures known as psammoma bodies ( macroscopically resemble
grains of sand )
they occur in some papillary cancers, as of thyroid gland and ovary, or in
meningioma (benign tumor arising in menings)
significance: -dystrophic calcification- sign of previous cell injury or cell
on the other hand- deposits of calcium may also cause severe disorders
and damage, eventually lead to death (atherosclerosis of heart coronary
arteries, calcification of heart valves)
3. Hyaline change
„Hyalin“ refers to any alteration within the cell or extracellular space
which gives a homogenous glassy eosinophilic appearance- hyaline change
does not represent specific alteration
 -intracellular hyalin
-hyaline droplets in proximal tubular epithelial cells of kidneyrepresent reabsorption of proteins that passed through damaged
glomerular membrane into primitive urine
-Russel bodies- aggregates of immunoglobulins in plasmacytes, most
commonly in chronic inflammmation
- viral inclusion within cytoplasm or nucleus
-alcoholic hyalin- aggregates of cytokeratin intermediate filaments
in cytoplasm of hepatocytes in alcoholic liver disease
-hyaline cell (Lomax-Azzopardi cells )= modified myoepithelial cells
in salivary gland tumors, hyaline appearance is caused by accumulation of
vimentin and cytokeratin IFs
 extracellular hyalin
-hyalinization of collagenous fibrous tissue means regressive change that
is represented by a decrease of a vascularity and and inrease of
thickness of collagen fibres - occurs for example in old scars
-hyaline arteriolosclerosis- change of small arteries and capillaries of
kidney in DM
-hyalinization of damaged glomeruli- nonspecific- hyalin appears to be a
complex of plasma proteins, basement membrane components and
mesangial matrix
-diagnosis of amyloidosis is based on a simple tinctorial property:
binding to cotton wool dye Congo red, with green birefringence under
polarized light, fulfills diagnostic criteria for amyloid
-amyloid represents a group of complex proteinaceous
substances that may be deposited in tissues and organs
-amyloid represents a heterogenous group of different fibrillary
proteins with different tissue distribution, origin and biochemical
classification of amyloid:
-systemic or localized
-primary, secundary or inherited
amyloid accumulates within tissues and organs either because of excess
synthesis or because of resistence to catabolism
common for all types of amyloid
-the term „amyloid“ means „starch-like“, and such as it is misleading
because amyloid is not a carbohydrate it shows stainability of fresh
tissue by iodine- similar to staining properties of starch - brown colour is
produced in tissues with amyloid deposits-grossly- when deposited in tissues in large amounts- the tissue becomes
pale, smooth and waxy in texture
-in histologic sections- amyloid stains with Congo red dye (amyloid appears
red with apple-green birefringence under polarized light)
-in hematoxylin-eosin it stains homogenous pink
-on electron microscopy- amyloid appears as non-branching fibrils 7,5 to
10 nm wide
The type of protein found in the amyloid deposits depend on the
underlying diseasefor example amyloid may occur in patients with multiple myelomaneoplastic proliferation of antibody-producing plasma cells- the amyloid is
composed of IgG light chains
-whatever the main constituent protein, the amyloid deposit also
contains a second substance known as a P component
- there are two major types of amyloid -and two important clinical
situations in which amyloid is deposited
 1) Amyloid of immunoglobulin origin - AL amyloid
-the protein is composed of fragments of the light (kappa or
lambda) chains of IgG
AL is produced - by neoplastic plasma cell in multiple myeloma or by
neoplastic cell of malignant lymphoma
 2) Amyloid of nonimmunologic origin - AA amyloid
-the protein in AA amyloidosis is derived from alfa 1- globulins of
plasma, that is synthesized in the liver and is elevated in chronic
inflammatory disorders
-clinical classification is based on the type of amyloid and tissue
1) Systemic amyloidosis with primary pattern of tissue distribution
most common type of systemic amyloidosis…..the origin of the fibril is an
IgG light chain or IgG heavy chain fragment, all patients have clonal
plasma cell proliferation (multiple myeloma, malignant lymphoma)
-deposits in heart, gastrointestinal tract, tongue, skin, nerves
-amyloid is of AL type
2) Systemic amyloidosis with secondary pattern of tissue distribution
-amyloid is found in liver, spleen, kidney, adrenal glands, GIT, skin
-amyloid is of AA type and derived from plasma alfa 1-globulins
-occurs in chronic inflammations, such as chronic osteomyelitis, chronic
pyelonephritis, tuberculosis, chronic inflammatory bowel disease
3) Localized amyloidosis
localized forms may be suspected because of organ involvementtongue, urinary bladder, ureter,urethra-always localized, lungs, skin,
conjuctiva-mostly localized…
-this type is usually associated with AL amyloid of multiple myeloma
or malignant lymphoma
-or it represents cardiac amyloid- heart failure
-or cerebral amyloid -amyloid is deposited in blood vessel walls
4) Amyloid in tumors
amyloid can occur in the stroma of various tumors of endocrine organs,
such as medullary carcinoma of thyroid gland ( tu derived from C cells
producing calcitonin)
in pancreatic islet cell tumors etc.
5) Heredofamiliar amyloidosis
Two form of inherited generalized amyloidosis: -both are rare
1) amyloid is derived from nonimmunoglobulin proteins of plasma amyloid is of AF type, sites of most severe involvement are heart muscle
(cardiac form), kidney (nephropathic form), neurons (neuropathic form)
2) amyloid is of AA type - in familial Mediterranean fever, a
disease characterized by fever and joint inflammations
6) Senile amyloidosis
amyloid of AS type- deposits of amyloid are seen in heart, pancreas,
spleen in old patients
effects of amyloid deposition
amyloid is deposited extracellularly, in basement membranes, in blood
vessel walls
organs involved by amyloid deposits are enlarged (hepatosplenomegaly)
most serious- involvement of kidney- may result in renal failure