Aetiology Pathogenesis 2024 - Copy.pptx

Aetiology and pathogenesis of diseases Overview Aetiology Pathogenesis Manifestations of disease Learning outcomes To define the terms used in describing the characteristics of diseases Explain the difference between aetiology and risk factors To understand the pathogenesis and characteristics of di...

Aetiology and pathogenesis of diseases Overview Aetiology Pathogenesis Manifestations of disease Learning outcomes To define the terms used in describing the characteristics of diseases Explain the difference between aetiology and risk factors To understand the pathogenesis and characteristics of diseases Aetiology and pathogenesis of diseases Overview Aetiology Pathogenesis Manifestations of disease Characteristics of Disease - overview Aetiology: Cause of a disease Pathogenesis: Mechanisms causing the disease Pathological & Clinical manifestations: Structural and functional features, symptoms, signs Complications: Secondary effect Prognosis: Outcome of a disease Epidemiology: The incidence, prevalence and population distribution of a disease Aetiology and pathogenesis of diseases Overview Aetiology Pathogenesis Manifestations of disease Aetiology (Cause) The initiator of the subsequent events resulting in patient’s illness (the causes of diseases) Genetic: – Inherited – Acquired (during conception or embryogenesis, or during post-natal life) Environmental: - Infectious agents: bacteria, virus, fungi, parasite - Chemicals - Physical: radiation, mechanical trauma Multifactorial (genetic and environmental) Multifactorial aetiology Diseases due to a combination of causes Proportionate risk of disease due to genetic or environmental factors Aetiology (Cause) Unknown aetiology: Classified as: idiopathic, primary, essential spontaneous, cryptogenic Risk factor: The aetiology of a disease is unknown, but the disease is observed in people with certain habits such as smoking, age, or occupations Aetiology and pathogenesis of diseases Overview Aetiology Pathogenesis Manifestations of disease Pathogenesis The pathogenesis of a disease is: The mechanism through which the aetiology (cause) operates to produce the pathological and clinical manifestations Examples of Pathogenesis Inflammation: A response to many micro-organisms and other harmful agents causing tissue injury Degeneration: A deterioration of cells or tissues in response to, or failure of adaptation to, a variety of agents Carcinogenesis: The mechanism by which cancer-causing agents result in the development of tumours Aetiology and pathogenesis of diseases Overview Aetiology Pathogenesis Manifestations of disease Symptoms and Signs Symptoms of a disease: What the patient suffers or patient's complaints Common symptoms: pain, fever, nausea Specific symptoms: diarrhoea or constipation, skin rash Signs of a disease What the doctor is looking for: body temperature, blood pressure Syndrome An aggregate of signs and symptoms or a combination of lesions without which the disease cannot be recognised or diagnosed Cushing’s syndrome: Obesity, hypertension, thinning skin that bruises easily, reddish-purple stretch marks on the thighs, stomach, buttocks, arms, legs or breasts etc. Due to too much adrenocorticotropic hormone (ACTH) Lesions Lesions: The structural or functional abnormality responsible for the ill health Example: Myocardial infarction, the infarct or patch of dead heart muscle is the lesion Complications Complications: The prolonged, secondary or distant effects of a disease Example: Lung embolism due to the thrombosis in the leg vein Prognosis The anticipated outcome (forecasting the known or likely course) of a disease Example: The 5-year survival prospects for lung cancer are about 5% The purpose is to plan appropriate treatment and to give useful information to individual patients The prognosis of a certain disease is influenced by medical or surgical intervention Epidemiology Pathology of the populations Determination of causes, incidence, mortality, characteristic behaviour of disease outbreaks affecting human populations Morbidity Morbidity of a disease: The disease state of an individual, or the incidence of illness in a population - The proportion of patients with a particular disease during a given year per given unit of population For example: WHO source: Morbidity of Influenza is about 5 – 10% in adults and 20 – 30% in children Mortality Mortality of a disease is the probability that death will be the end result of that disease Mortality is expressed usually as a percentage of all those patients presenting with the disease For example: the mortality rate of myocardial infarction could be stated as 50% under defined circumstances Prevalence Prevalence of a disease - The total number of cases of a given disease in a specified population at a designated time Different from morbidity (incidence), which refers to the number of new cases in the population at a given time For example: The prevalence of diabetes in UK is 6% in 2013 (report Feb 2014) Relationship Aetiology Pathogenesis Lung cancer Disease (structural & functional damage) Complication Relationship Aetiology Pathogenesis Disease (structural & functional damage) Complication Hypertension In lecture test question True or False The following are correctly paired a) Idiopathic – cause unknown b) Pathogenesis – direct cause of disease c) Congenital – present at birth d) Prognosis – likely disease outcome e) aetiology – mechanisms of disease Summary Disease: Characteristics Aetiology (Cause): Genetic/environmental/multifactorial Pathogenesis Terminology: symptom / sign / syndrome Epidemiology: morbidity, mortality, prevalence