Lecture 1 - Introduction - 2 Sep 2006

Teaching in Pathology Theory Practicals

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Theory

:

Lectures Clinico-pathological

correlations Lectures are introduction to topics. Reading a text book is essential for success in Pathology 2

Practicals: - Histopathology - Gross - Microscopic - Haematology - Microscopic - Clinical Chemistry - Case discussions and evaluation of laboratory data 3

Examinations: Five Incourse Assessments Each Assessment has two components: i. Theory (60%) (MCQs - Single response & True/False types, Short answer questions & Long essay) & ii. Practical (40%) Practical Examination Materials used in the practical examinations are NOT exactly those used in the practical classes but are the 4 same lesions.

Lecture 1 Introduction to Pathology

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PATHOLOGY GREEK Pathos

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Suffering

Logos

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Discourse

(Scientific study of disease (suffering Scientific study of the way things go wrong 6

Pathology includes:  Microbiolgy

 Virology

 Haematology

 Transfusion Medicine

 Chemical Pathology

 Toxicology

 Genetics

 Histocompatibility and

 Immunology

 immunogenetics Histopathology

 Neuropathology

 Oral Pathology

 Forensic pathology

 Veterinary pathology 7

Why study Pathology ? - Study of disease is essential to the study of medicine - Understanding the mechanisms of disease is invaluable for patient care (diagnosis, treatment, prevention) 8

DISEASE -

Departure from the normal structure and function of an organism

Failed or inadequate adaptation to changes in the internal and external environment. FAILED HOMEOSTASIS 9

DISEASE -

Disease often arises from perversion of homeostasis

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Failures of homeostatic adaptation are self-promoting (i.e one damn thing leads to another)

Encounters between the body and ‘invaders’ more often end in draws rather than a clear win -

Rapid bodily response to injury often leads to an over-kill

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DISEASE -

Inadequate response – the young

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Unwanted side effects of homeostatic mechanisms i.e. the enemy within

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DISEASE -

The young produce antibodies against invaders

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The antibodies damage self tissues in middle age

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Disease is the other side of the coin of Survival 12

Six definitions of ‘Normal” in common clinical use Property Distribution of diagnostic test results has a certain shape

Term Gaussian

Consequences Ought to occasionally obtainmore values to haemoglobin etc.

Lies within a preset percentile Percentile of previous diagnostic test results

All diseases have the same prevalence. Patients are normal only until they are worked up

Carries no additional risk of morbidity or mortality

Risk factor

Assumes that altering a risk factor alters rise

Socially or politically aspired to

Culturally desirable

Confusion over the role of medicine in society

Range of test results beyond which a specified disease is with known probability, present or absent

Diagnostic

Need to know predictive values that apply in our practice

Range of test results beyond which treatment does more good than harm

Therapeutic

Need to keep up with knowledge about treatment 13

Top 20 non-diseases (voted on bmj.com by readers), in descending order of “non-diseaseness” 1. Ageing

11. Chidbirth

2. Work

12. Allergy to the 21st century

3. Boredom

13. Jet lag

4. Bags under the eyes

14. Unhappiness

5. Ignorance

15. Cellulite

6. Baldness 7. Freckles

16. Hangover 17. Anxiety about penis size/penis envy

8. Big ears

18. Pregnancy

9. Grey or white hair

19. Road rage

10. Ugliness

20. Loneliness

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Characteristics of Disease: -

Definition

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Nomenclature

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Aetiology (cause)

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Pathogenesis (mechanism)

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Manifestation (anatomical, functional, clinical)

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Complication

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Prognosis (outcome)

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Epidemiology

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Characteristics of Disease

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Disease Nomenclature Acute

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rapid onset

Chronic

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slow, prolonged

Benign

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not likely to kill; recovery likely

Malignant

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likely to kill; lethal; deadly; recovery unlikely

Eponymous names

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persons, places

Syndromes

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combinations of symptoms and 17 signs or lesions

Prefixes: Commonly used prefixes and their meanings are:  ana-, meaning absence (e.g anaphylaxis)  dys-, meaning disordered (e.g. dysplasia)  hyper-, meaning an excess over normal (e.g. hyperthyroidism)  hypo-, meaning a deficinecy below normal (e.g. hypothyroidism)  meta-, meaning a change from one state to another (e.g. metaplasia)

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Suffixes:

Commonly used suffixes and their meanings are:  -itis, meaning an inflammatory process (e.g appendicitis)  -oma, meaning a tumour (e.g. carcinoma)  -osis, meaning state or condition, not necessarily pathological (e.g. osteoarthrosis)  -oid, meaning bearing a resemblance to (e.g. rheumatoid disease)  -penia, meaning lack of (e.g. thrombocytopenia)  -cytosis, meaning increased number of cells, usually in blood (e.g. leukocytosis)  -ectasis, meaning dilatation (e.g.bronchiectasis)  -plasia, meaning a disorder of growth (e.g. hyperplasia)  -opathy, meaning an abnormal state lacking specific characteristics (e.g.lymphadenopathy)

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Classification of Disease: 

Congenital

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Present at birth

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Acquired

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Environmental

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Inflammatory

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Vascular disorders

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Metabolic

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Degenerative

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Growth disorders

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Iatrogenic

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A General classification of Disease

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Cause Inherited (genetic) Congenital Late appearing Consequent upon growth or ageing Infective Inflammatory Vascular Metabolic/toxic Physical or chemical trauma Neoplastic Environmental Idiopathic (unknown) -

Disease Example Cystic fibrosis Huntington’s disease Senile dementia Pneumonia Eczema (dermatitis) Myocardial Infarction Diabetes A burn lung cancer Starvation Sarcoidosis

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How do we study disease? 

Post-mortem examination (autopsy; necropsy)

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Gross pathology (naked-eye – macroscopic)

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Light microscopy

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Histochemistry

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Immunohistochemistry / Immunofluorescence

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Electron microscopy

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Biochemical techniques (tissues, fluids)

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Haematological techniques

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Cytology

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Cell cultures

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Molecular pathology

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Microbiology (microscopy, culture, sensitivity tests)

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Value of the Autopsy  Assure quality control of medical care • Establish or confirm cause of death • Confirm, modify or refute clinical diagnises • Monitor therapeutic responses • Evaluate new operative, pharmacologic and diagnostic approaches  Enhance education  Foster research • Discover new or previously unrecognised diseases • Provide essential information on disease manifestations • Provide essential organs and tissues for research and transplantation  Heighten total patient care • Offer general psychoemotional benefits to the family • Establish basis of genetic counseling 

Improve public health

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Value of the Autopsy  Investigate and identify environmental, occupational and life style related diseases  Evaluate new prostheses (e.g cardiac, vascular, orthopedic)  Allow forensic diagnoses  Improve hospital reimbursements and efficiency through more accurate diagnostic-related groups (DRGs) 

Improve accuracy of vital statistics

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Provide information and assistance to legal and judicial systems

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Partial list of Infectious Diseases discovered or clarified by Autopsy since 1950 Pneumocystis pneumonia Legionnaire’s disease Whipple’s disease Viral hepatitis Spongiform encephalopathy (Creutzfeldt-Jacob disease) Progressive multifocal leukoencephalopathy Acquired immunodeficiency syndrome Microsporidiosis Congenital infections (e.g toxoplasmosis, cytomegalovirus) Disseminated fungal diseases

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