Download Pathophysiology of blood

Pathophysiology of red and white
blood cells, disturbances of
hemostasis and coagulation
Prof. J. Hanacek, MD, PhD.
Remarks to physiology of blood
1. Main functions of blood
• Transport of various substances (O2, CO2, nutrients,
metabolites, minerals, ......)
• Transport of heat (heating, cooling)
• Signal transmission (hormons,...)
• Carrier proteins – e.g. albumin
• Buffering and defence systems (antibodies, white
blood cells, oxidants-antioxidants, buffer systems)
• Remove products of metabolism
• Body homeostasis-temperature, water, electrolytes
2. Composition of blood
• Blood cells (RBC, WBC, platelets)
• Plasma (electrolytes, nutrients, metabolites,
proteins, fat, carbohydrates, vitamins, gases....)
3. Development of blood cells
• Hematopoietic tissues - red bone morrow (in adult)
- spleen, liver, other organs (pathologic
conditions)
• Pluripotent stem cells  myeloid, erytroid, lymphoid
 precursor cells

hematopoietic growth factors
• Myeloid precursor cells  myelopoiesis  monocytes 
 tissue macrophages  (in bone morrow)

 mast cells,
maturation
eosinofils,
neutrophils,
basophils
• Lymphoid precursor cells  lymphopoiesis  LyT, LyB
 (in spleen and lymph nodes)
maturation
4. Factors and hormones involved in
prolifaration and maturation of blood cells
• Erytropoietin (EPO) proliferation and maturation of ER
(from kidney)
• Thrombopoietin  prolifaration and maturation of
(from kydney)
• Paracrine factors:
megacaryocytes  platelets
- colony stimulating factors (CSF)
- stem cells factor  release CSF and IL
3, 6, 11, 12
 Androgens, Thyroid hormons
(in bone morrow)
CSF and IL formation are inhibited by TGF beta and
by TNF alfa
A. Abnormalities of red blood cells
I. abnormalities in mass of RBC
1. Anemias
2. Polycythemias
Anemias
Definition: Reduction below the normal level in the number
of RBC, the quantity of Hb, and the volume of
packed RBC (Htk) per 100 ml of blood
Classification:
• According to the mean corpuscular volume (MCV) of RBC:
Normal MCV  90 fl
- micro- normo cytic anemia
- macro
• According the mean corpuscular Hb (MCH):
Normal MCH  30pg
- hypo
- normo
chromic anemia
- hyper
Etiopathogenetic classification
a) reflects steps in Er-poiesis   RBC production
 defective RBC production
b) reflects life-span of Er   RBC loss
Causes leading to defective RBC production:
● hemoglobinopaties - e.g. sickle cells disease,
● impaired globin synthesis – e.g. thalassemias
● RBC membrane defects – e.g. hereditary spherocytosis
● enzyme deficiency - ATP due to pyruvate kinase
-  G- 6 - phosphate dehydrogenase
Causes leading to decreased and/or defective RBC production
Disseminated malignancies - e.g. brest cancer, leukemias...
Serious chronic disease - e.g. inflammatory, endocrine....
Lack of essential vitamins - e.g. B12, folic acid, C vitamin...
Lack of iron
Bone morrow failure
Causes leading to RBC loss
Bleeding - e.g. peptic ulcer, polyps in colon, GIT malignancies,
hemorhoids, esophageal varices...
Hemolysis - e.g. due to decreased resistance of RBC (defects in
RBC membrane, defects in RBC metabolism) or
due to changed microenvironment surrounding RBC
(mechanical, imunologic, toxic influences)
Aplastic anemia (AA) – insufficient number of RBC is
produced
Pathogenesis: - multifactorial disease genetically determined
- primary proliferation defect of the hemopoietic
system
- immune reaction directed against hemopoietic
system
Mechanisms probably involved in AA development
• immune reaction mediated by T-cells or less frequently
by B-cells
• many IL are produced in excess in patients with AA, e.g.
IL-2, TNF – they inhibit activity of bone morrow function
• abnormal sensitivity of hemopoietic cells is assumed, so
probably, hemopoietic tissue is primarilly diseased
Cosequences:
If the immune reaction is strong enough it wipes out abnormal
cells  acute severe aplasia
If the immune reaction is rather weak  mild chronic
pancytopenia will develop
Causes of AA
• Direct toxicity – Iatrogenic causes
- radiotherapy
- chemotherapy
– Benzen
– Intermediate metabolites of some common
drugs
• Immune-mediated causes
– Iatrogenic causes, e.g. - transfusion-associated
graft-versus host disease
- Eosinophilic fasciitis
- Hepatitis-associated disease
- Pregnancy
- Intermediate metabolites of some common drugs
- Idiopathic AA
Iron deficiency anemias (IDA)
• Characteristics - serum Fe<0.4mg/l, serum ferritin
• Main causes: - Blood loss – the most common cause of IDA
in adults (0.5mg Fe lost/1ml blood)
- Fe recycling is decreased (the 2nd most common
worldwide)
– occurs with chronic infections (Fe regained by
the macrophages  decreased releasing
of Fe for Hb production  reuse of Fe
- Fe uptake from GIT is too low (malnutrition)
- Fe absorbtion is reduced due to:
1. Achlohydria (atrophic gastritis...)
2. Malabsorption in upper part of GIT,
Fe-binding food components (fytates, tannic acid)
-Fe requirement (growth, pregnancy, breast-feeding)
- Apotransferrin defect
Iron deficiency  inhibition of Hb synthesis 
 hypochromic microcytic anemia
Sideroblastic anemia
– hypochromic anemia caused by
inability of RBC to use of Fe in Hb synthesis
Pathogenesis:
genetic defect linkaged to X-chromosome
(men are more severely affected)
mitochondrial lesions  sequestration of Fe complexes
in the mitochondria of erythroblasts  sideroblasts
Megaloblastic anemia due to abnormalities in
DNA synthesis
Main causes: - abnormalities in the absorbtion and metabolism
of folate or B12 vitamin
Consequencies:
inhibition of DNA synthesis  cell cycle is slowed down
during erythropoiesis  delay in RBC maturation
Hb synthesis in cytoplasm is unchanged  size of ER
(megaloblasts)  megalocytes in blood
Megalocyte = MCV > 100 fl
formation of granulocytes and megacaryocytes is also
disturbed
premature destruction of megaloblasts in bone morrow
(inefficient erythropoiesis) and shorten life of megalocytes
(premature hemolysis)
Main disorders of folate absorbtion and metabolism
•  folate uptake
•  folate requirement
• malabsorbtion, e.g. diseases of small intestine(terminal part)
• cobalamine deficiency
Causes: - too litle folate uptake with food
- intrinsic factor deficiency
- competition for vitamin B12 (bacterias, broad
fish tapeworms- Diphyllobothrium latum)
- absence of the terminal ileum or its
inflammation- site of absorbtion of cobalamine
- defective transcobalamin II
Pernicious anemia (PA)
- the most common type of megaloblastic anemia
- „pernicious“= highly injurious and in the past fatal
Pathogenesis:
defective gastric secretion of intrinsic factor
- congenital deficiency
- atrophy of gastric mucosa
- partial or complex gastrectomy
Consequences:
- megaloblastic anemia
- neurologic disorders
Posthemorhagic anemia
• normochromic, normocytic anemia caused by sudden loss
of blood
Main cause – strong bleeding, lost of large amount of blood
during relatively short time
Course of posthemorhagic anemia
1st step – substitution of lost plasma volume plus Er from depots
2nd step – acceleration of hemopoiesis   mass of Er in bone
morrow
Recovery of normal number of Er after bleeding – afer 4 – 6 weeks
Recovery of normal Hb concentration can last 6 – 8 weeks
Hemolytic anemias (HA)
Schyzocytes
Characteristic signs:
– premature destruction of Er
– erythropoiesis can be normal
– abnormally short life span of Er
– erytropoiesis is accelerated
Causes and pathogenetic mechanisms of HA development
– inherited
– acquired
Causes of acquired HA
– infections, systemic diseases (e.g. lupus erythematosus)
– poisons – drugs, toxins (endo- or exogenous)
– disturbances of liver and kidney
– abnormal immune reactions – e.g. transfusion reaction,
hemolysis of newborns, autoimmune reactions
Causes and mechanisms of inherited HA
Mechanisms: – defect of Er membrane
– defficiency of glycolytic enzymes
– disturbances in Hb synthesis
– others
Other pathomechanisms particiating in HA development
– physical destruction – trauma, arteficial heart valves,
super-long march or run ?
– heat and irradiation
Disturbances of white blood cells
1. Leukemias
Main pathogenic mechanisms
– structural changes of the normal genes (protooncogens 
 oncogens)
– loss or inactivating genes (antioncogens)
– activation of oncogens and loss of antioncogens
leads to: – increased proliferative activity of the cells
– cell loses ability to diferentiate and to apoptosis
Some oncogens related to leukemias:
– Philadelphia chromosome =translocation of ABL gene from
chromosome 9 to chromosome 22 and its fusion to gene BCR
Acute myeloblastic leukemia (AML)
- disseminating, clonal proliferation of inmatured
hematopoietic cells
- 90% of AL in adults is myeloid type
Possible causes of AML:
– irradiation
– chemical agents, e.g. benzene
– viruses
Main manifestations of AML:
- cytopenia and blast present in blood
- neutropenic fever
- anemia, thrombocytopenia
- hyperuricemia, hyperkaliemia, hyperphosphatemia
- number of blast cells in peripheral blood > 50,000/l 
 leucostasis
Consequencies:
blood viscosity
rigidity of blast cells increased risk of leucostasis
agglutination

- bleedinng to brain
- lung and kidney failure
Disorders of hemostasis
• Hemostatic system is composed of:
– plasma coagulation factors
– platelets
– vessel wall
– inhibitory (anticoagulant) factors
– fibrinolysis system – dissolving excessive fibrin clots
Hemorhagic diathesis (HD) = increased bleeding tendency
Main causes: - disorders of coagulation, fibrinolysis, platelets
- vascular defects
Consequences: • if coagulation and fibrinolysis is inadequate
- minimal mechanical injury  hematomas
 bleeding into
joints
• if trombocytes and vascular wall are damaged
- punctate, tiny cutaneous bleeding
Pathogenetic mechanisms leading to disturbancies
of coagulation and fibrinolysis in patients suffering
from sepsa
activation tissue
factor
sepsa

(endo)toxin

cytokines
inhibition fibrinolysis

by PAI-1
depression of
inhibitory system
deposition of fibrin

organ failure
Levi et al. Eur J Clin Invest 1997;27: 3-9