Causes and Effects – Genetic and Environmental

Module 8: Non-Infectious Disease and Disorders

Part 2: Cause and Responses

  • Instructor: Mrs. Menon

Overview of Non-Infectious Diseases

  • Inquiry Question: Do non-infectious diseases cause more deaths than infectious diseases?

  • Topics to Investigate:

    • Genetic diseases

    • Diseases caused by environmental exposure

    • Nutritional diseases

    • Cancer

  • Definition: Non-infectious diseases are those diseases that are not caused by pathogens and are not contagious.

  • Historical Context:

    • Infectious diseases were historically the main cause of death globally.

    • In developing regions, infectious diseases continue to be prevalent.

    • With advancements in antibiotics and vaccination, infectious diseases are no longer the leading causes of death in developed countries.

    • Current Status: Non-infectious diseases are responsible for a significant proportion of deaths in both developed and developing countries.

Causes of Non-Infectious Diseases

  • Non-infectious diseases account for nearly two-thirds of deaths worldwide.

  • Risk Factors:

    • In Developed Countries:

    • Poor diet

    • Tobacco use

    • Alcohol consumption

    • Physical inactivity

    • In Developing Countries:

    • Lack of food

    • Limited access to clean water

    • Poor hygiene

Leading Causes of Death (2022)

  • Data Source: AIHW 2024, Deaths in Australia

  • Top Causes:

    1. Coronary heart disease

    2. Dementia (including Alzheimer’s disease)

    3. COVID-19

    4. Cerebrovascular disease

    5. Lung cancer

Categories of Non-Infectious Diseases

  • Genetic/Inheritated Diseases:

    • Caused by changes in genetic information.

    • Example Diseases: cystic fibrosis, hemophilia, albinism, Down syndrome, sickle-cell anemia, phenylketonuria, Huntington's disease.

  • Nutritional Deficiencies/Diseases:

    • Caused by excess or inadequate diet.

    • Example Diseases: scurvy, rickets, liver disease, obesity.

  • Environmental Diseases:

    • Result from exposure to environmental factors.

    • Example Conditions: hypersensitivity (allergies), heavy metal poisoning, asbestosis, industrial deafness.

  • Cancers:

    • Generalized cancers and those affecting specific tissues or organs (e.g., lung, skin, brain, cervical, prostate).

  • Other Conditions:

    • Some physiological malfunctions, mental illnesses, and aging-related diseases.

Inherited/Genetic Diseases

  • Definition: Genetic diseases are transmitted genetically and caused by mutations in genes or chromosomes.

    • Types of Mutations:

    1. Single gene abnormalities

    2. Chromosomal abnormalities

Single Gene Abnormalities

  • Definition: Defect arising in a single gene due to mutation.

  • Cause: Often inherited from parents.

  • Types of Onset:

    • Recessive or dominant alleles

    • Example Genetic Diseases: cystic fibrosis, hemophilia, thalassemia, phenylketonuria (PKU).

Sickle Cell Anemia

  • Description: A single gene abnormality affecting hemoglobin.

  • Function of Hemoglobin (Hb): A protein that carries oxygen from the lungs to the body.

  • Mutation: In sickle cell anemia, altered hemoglobin (Hb S) sticks together when oxygen levels are low, forming long fibers.

  • Effect: These fibers distort red blood cells into a sickle shape, reducing oxygen transportation efficiency and flow through vessels.

Cystic Fibrosis

  • Cause: Mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7.

  • Function of CFTR: Regulates sodium chloride movement in and out of cells.

  • Result of Mutation: Causes excessively thick mucus in mucus-secreting organs.

  • Genetic Transmission: CFTR is a recessive gene, requiring two faulty alleles to develop the disease.

  • Ethnic Variation: Occurrence of cystic fibrosis varies with ethnic groups.

Organs Affected by Cystic Fibrosis

  • Areas Affected:

    • Respiratory system

    • Digestive system

    • Reproductive systems

    • Sweat glands

  • Impact of Thick Mucus:

    • Blocks passageways in lungs

    • Causes significant breathing and digestion issues.

Symptoms of Cystic Fibrosis

  • Recurrent and severe chest infections.

  • Malabsorption of nutrients: failure to thrive.

  • Passing large, foul-smelling stools.

  • Diabetes and excess salt in sweat.

  • Liver failure and infertility.

  • Average Life Expectancy: 30–40 years.

Treatment for Cystic Fibrosis

  • Current Status: No cure available; treatment focused on symptom management.

  • Treatment Approaches:

    • Nutritional supplements to enhance digestion.

    • Daily physiotherapy and breathing exercises to clear mucus.

    • Antibiotics to control infections.

    • Surgical lung transplant options for advanced cases.

    • Research into gene therapy as a potential future treatment.

Phenylketonuria (PKU)

  • Cause: Mutation of the gene on chromosome 12 coding for phenylalanine hydroxylase (PAH).

  • Function of PAH: Enzyme necessary for breaking down the amino acid phenylalanine.

  • Consequences:

    • Accumulation of phenylalanine leads to severe intellectual disabilities and behavioral issues.

    • Inheritance: Autosomal recessive; newborns are routinely tested.

    • Dietary Restrictions: Lifelong low-protein diet avoiding foods like milk, nuts, and meats.

Chromosomal Abnormalities

  • Definition: Changes to the chromosome structure that can affect several genes.

  • Types of Chromosomal Abnormalities:

    1. Incorrect number of chromosomes (e.g., trisomy, monosomy).

    2. Structural changes in chromosomes (deletions, additions, alterations).

Incorrect Number of Chromosomes

  • Causes of Incorrect Number:

    • Non-disjunction: Faulty chromosome separation during cell division.

    • Result: Zygote has incorrect chromosome numbers.

    • Trisomy: One extra chromosome in the zygote (total chromosomes > diploid number).

    • Monosomy: One chromosome missing from a pair (total chromosomes < diploid number).

Syndromes from Chromosomal Abnormalities

  • Definition: Syndromes are a group of symptoms occurring together characterizing specific diseases.

  • Trisomy or Monosomy determines type of syndrome.

Down Syndrome

  • Cause: Extra chromosome 21 (Trisomy 21).

  • Incidence: Most common trisomy (1 in 800 live births).

  • Characteristics:

    • Distinctive facial features (flattened skull, flat-bridged nose, almond-shaped eyes).

    • Intellectual disability, short stature, heart defects, and susceptibility to infections.

Klinefelter Syndrome

  • Cause: Trisomy involving sex chromosomes (XXY).

  • Characteristics:

    • Lower testosterone levels, small testes, sterility.

    • Taller than average stature, behavioral and learning difficulties.

Diseases Caused by Environmental Exposure

  • Definition: Result from interaction with environmental factors.

  • Types:

    • Lifestyle Diseases: Result from personal lifestyle choices (Cardiovascular diseases, diabetes).

    • Physical Factors: Environmental exposures (UV radiation causing skin cancer).

    • Chemical Exposure: Long-term exposure to harmful chemicals (Asbestos, lead).

Lifestyle Diseases

  • Causes: Factors such as insufficient physical activity, excessive alcohol use, stress, smoking, and an unbalanced diet (high in kilojoules, saturated fats).

  • Examples:

    • Hypertension, stroke, heart disease, and diseases from substance abuse.

Atherosclerosis

  • Description: A type of cardiovascular disease referred to as “hardening of the arteries”.

  • Causes: Lifestyle risk factors such as tobacco use, unhealthy diet, physical inactivity, and excessive alcohol consumption.

UV Radiation

  • Impacts: Excessive exposure leads to skin cancer through DNA changes in skin cells.

  • Consequences: Abnormal cell division leading to various skin cancers (basal cell carcinoma, squamous cell carcinoma, malignant melanoma).

Mesothelioma

  • Overview: Cancer affecting the mesothelial cells in the pleura membrane surrounding the lungs.

  • Cause: Long-term exposure to asbestos fibers.

  • Global Context: Australia has the highest incidence of mesothelioma (40 cases per million people).

Cancer Development Process

  • Initial Stage: Begins with gene mutations affecting cell division processes.

  • Link to Exposure: Asbestos exposure increases mutation risks leading to mesothelioma.

Symptoms and Treatment of Mesothelioma

  • Symptoms: Shortness of breath, chest pain, weight loss, loss of appetite, fatigue, fevers, night sweats, anemia.

  • Treatment Approaches:

    • Focus on symptom control and life extension.

    • Difficulty in surgical removal of tumors.

    • Use of chest tubes to alleviate pressure.

    • Research into immunotherapies and new drug combinations for treatment.

Risk Factors for Mesothelioma

  • Direct relationship between exposure duration and risk of developing the disease.

  • Development Timeline: Mesothelioma can take 20 to 50 years to arise post-exposure to asbestos.