exam practice

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Birth Defects

  • Definitions: Birth defects may arise from genetic or environmental factors.

    • Fetal Alcohol Syndrome (FAS): A condition caused by maternal alcohol consumption during pregnancy, leading to various physical and neurodevelopmental issues.

Genetic Factors

  • Birth defects can be present due to mutations in DNA, abnormal chromosomal arrangements, or changes in chromosome number. These defects may be present at birth.

Single Gene Disorders

  • Definition: Caused by a defective allele at a specific locus; they occur due to issues at a specific gene or allele.

  • Unlike multifactorial conditions, they are not influenced by multiple genes.

  • Causes lead to the production of abnormal proteins as the gene codes for the incorrect protein.

  • Types:

    • Autosomal Dominant Disorders:

    • Affects chromosomes 1-22.

    • Presence in every generation; affected individuals may express different levels of severity and may not always show symptoms.

    • Examples include:

      • Achondroplastic Dwarfism: Homozygous dominant is often fatal.

      • Huntington’s Disease: Characterized by a later age of onset.

      • Marfan’s Syndrome: Affects elastic fibers significantly affecting the skeleton and cardiovascular system with a later onset.

      • Neurofibromatosis: Characterized by the formation of tumors in Schwann cells.

    • Key Terms:

      • Reduced Penetrance: The dominant gene is inherited but not expressed.

      • Variable Expressivity: Symptoms vary widely among individuals.

    • Autosomal Recessive Disorders:

    • They require two copies of the recessive allele for the disease to manifest.

    • Often involve early onset conditions classified as “inborn errors of metabolism.”

    • Examples include Phenylketonuria (PKU) and Tay-Sachs Disease.

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X-Linked Recessive Disorders

  • Definition: These disorders are transmitted through the X chromosome, affecting males more severely due to their hemizygous state.

    • Examples include:

    • Red-Green Color Blindness and Hemophilia.

    • Fragile X Syndrome: Characterized by a fragile site on the X chromosome, leading to the most common inherited form of intellectual disability.

Multifactorial Inheritance

  • Definition: Caused by combinations of multiple genes and often environmental factors.

  • The risk of reoccurrence increases as the severity and occurrence in relatives rise.

Chromosomal Disorders

  • Alterations in structure or number of chromosomes; include:

    • Structural Changes: Breaks, rearrangements, or deletions of chromosomes.

    • Numerical Changes: Usually occur by nondisjunction.

    • Aneuploidy: Abnormal number of chromosomes (e.g., Monosomy and Trisomy).

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Mitochondrial Gene Disorders

  • Disorders that arise from mutations in mitochondrial DNA, typically inherited maternally.

    • Examples of Environmental Teratogens:

    • Fetal Alcohol Syndrome: Associated with ~2% of all births, potential for intellectual delay.

    • Toxoplasmosis: Associated with exposure to cat litter.

    • Rubella and Cytomegalovirus: Infectious diseases linked to congenital conditions.

Diagnosis of Genetic Disorders

  • Methods:

    • Carrier Screening: Testing parents for genetic conditions.

    • Pre-implantation Genetic Analysis: Used in IVF to test embryos.

    • Genetic Counseling: Discussion of personal genetics and risks.

    • Prenatal Diagnosis: Testing methods such as alpha-feto-protein (AFP) blood tests and ultrasonography.

    • Amniocentesis: Sampling amniotic fluid containing fetal cells for genetic testing.

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Cancer Introduction

  • Definition: Cancer is characterized by altered cell differentiation and uncontrolled growth, usually stemming from gene abnormalities that disturb the cell cycle.

  • Neoplasm: An abnormal mass of tissue that grows in an uncontrolled manner, can be benign or malignant.

    • Benign Tumors: Resemble normal cells, grow slowly, do not invade other tissues.

    • Malignant Tumors: Grow rapidly, invade other tissues, may metastasize to other body parts.

Characteristics of Cancer Cells

  • Anaplasia: Loss of differentiation, resembling fetal cells.

  • Genetic Instability: Increased rates of uncorrected mutations.

  • Loss of Contact Inhibition: Cells continue to grow after reaching adjacent cells.

  • Immortalization: Cancer cells can proliferate indefinitely due to enzymes like telomerase.

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Growth of Cancer Cells

  • Mechanisms:

    • Direct Invasion: Cancer cells secrete enzymes to break down surrounding tissues.

    • Seeding: Cells may spread via body cavities.

Etiology of Cancer

  • Multifactorial:

    • Involves both genetic factors and external influences such as carcinogens and mutagens.

    • Cancer Associated Genes: Include proto-oncogenes (gain-of-function mutations) and tumor suppressor genes (loss-of-function mutations).

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Diagnosis and Staging of Cancer

  • Staging: Determined by size and extent of tumors, often using the TNM system (Tumor, Nodes, Metastasis).

  • Grading: Based on histological characteristics (G1 to G4), indicating differentiation and growth rate.

Clinical Manifestations and Implications

  • Symptoms: Disruption of tissue integrity, fatigue, anemia, etc.

  • Treatment Options: Surgery, radiation, chemotherapy, and targeted therapies.

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Fluid and Electrolyte Disorders

  • Terminology:

    • Edema: Increased interstitial fluid primarily due to fluid volume overload or increased capillary permeability.

    • Pitting Edema: A condition in which indentation remains after pressure is applied to the skin.

Causes and Treatment of Edema

  • Types of Edema:

    • Nonpitting Edema: Accumulation of proteins in the tissue.

    • Effusion: Accumulation of fluid in body cavities.

    • Anasarca: Severe generalized edema.

    • Ascites: Excess fluid in the peritoneal cavity due to liver issues.

    • Transudate vs. Exudate: Transudate is non-inflammatory; exudate is associated with inflammation.

Management Strategies

  • Treatments: Diuretics, compression devices, and elevation.

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Disorders of Thirst

  • True Thirst: Occurs due to a decrease in plasma volume or dehydration.

  • Compulsive Water Drinking: Also known as psychogenic polydipsia, is characterized by excessive water intake unrelated to physiological needs.

Diabetes Insipidus

  • Definition: A condition resulting from inadequate levels of ADH, leading to excessive urination (polyuria) and thirst.

  • Syndrome of Inappropriate Antidiuretic Hormone (SIADH): Opposite of diabetes insipidus; leads to excess fluid retention.

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Isotonic Changes in Fluid Balance

  • Hypovolemia: Reduction in blood volume leads to decreased skin turgor and postural hypotension.

  • Hypervolemia: Results from fluid overload; manifests with jugular vein distension and pulmonary edema.

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Electrolyte Disorders - Sodium Balance

  • Hyponatremia: Low sodium levels can lead to cerebral edema and neurological complications.

    • Treatment involves careful fluid restriction and possibly sodium replacement.

  • Hypernatremia: High sodium levels, leading to cellular dehydration and potentially severe neurological symptoms.

Potassium Disorders

  • Hypokalemia: Low potassium levels, leading to muscle weakness and cardiac arrhythmias.

  • Hyperkalemia: High potassium levels can cause cardiac issues, especially in the setting of renal dysfunction.

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Calcium and Phosphate Disorders

  • Hypocalcemia and Hypercalcemia: Both conditions affect neuromuscular function significantly, leading to symptoms ranging from muscle spasms to arrhythmias.

  • Hypophosphatemia and Hyperphosphatemia: Both influence bone health and energy metabolism significantly.

Assessment of Fluid and Electrolytes

  • Suggested evaluation includes tracking intake vs. output and monitoring serum electrolyte levels.

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Acid-Base Disturbances

  • Normal pH range: 7.35 - 7.45; deviations can indicate critical health issues.

  • Respiratory Acidosis/Alkalosis: Results from alterations in CO2 levels due to ventilation abnormalities.

  • Metabolic Acidosis/Alkalosis: Result from altered bicarbonate or acid levels, with several clinical causes.

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Compensation Mechanisms in Acid-Base Balance

  • Includes chemical buffer systems and respiratory adjustments.

  • Patient assessments focus on electrolyte and gas exchange efficiency, with interventions tailored accordingly.

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Stress and Adaptation Responses

  • Stress responses involve a combination of hormone release and autonomic nervous system activation.

  • Various stages include: 1. Alarm Reaction, 2. Resistance (Adaptation), 3. Exhaustion.

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Hormones Released During Stress

  • Catecholamines (e.g. Epinephrine, Norepinephrine): Increase blood glucose, cardiac output, and oxygen supply.

  • Glucocorticoids (e.g. Cortisol): Alter metabolism and suppress immune response.

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Coping with Stress: Factors

  • Effectiveness relies on factors like time, gender, psychosocial support, and overall health.

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Hypercoagulation Disorders

  • Involves conditions where the blood coagulates excessively, predisposing to thrombosis.

  • Can be primary or induced by various health issues.

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Neoplastic and Non-Neoplastic Disorders of Coagulation

  • Include disorders either leading to excessive clotting or bleeding, with underlining etiologies often influenced by genetics or environmental factors.

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Anemia: Overview and Classifications

  • Not a standalone disease; it reflects underlying health issues. Major types: Blood loss, hemolytic, and those resulting from decreased RBC production.

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Clinical Manifestations of Anemia

  • Symptoms vary based on severity and include fatigue, pallor, and in severe cases, risk for cardiac complications.

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Sickle Cell Disease

  • A genetic disorder marked by misshapen RBCs leading to obstruction of flow, resulting in pain and organ damage. Treatment aims at symptom management and prevention of crises.

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Neutropenia and Leukopenia

  • Defined by low WBC counts leading to increased infection risk; often requiring protective measures.

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Mononucleosis

  • Usually caused by Epstein-Barr virus; symptoms include fatigue, sore throat, and swollen lymph nodes.

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Leukemia Overview

  • Characterized by unregulated proliferation of hematopoietic stem cells leading to excessive but immature WBC production. Treatment usually involves chemotherapy and potentially stem cell transplantation.

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Classifications of Leukemia

  • Classified based on the cell type involved (e.g., lymphoblastic, myelogenous) and the onset speed (acute vs. chronic).

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Plasma Cell Dyscrasias and Multiple Myeloma

  • Marked by excessive monoclonal immunoglobulin production, leading to various complications, notably bone pain and fractures. Treatment focuses on high-dose chemotherapy and stem cell transplantation.

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Disorders of Immune Response

  • Immunodeficiency disorders stem from congenital or acquired failures, increasing susceptibility to infections.

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Acquired Immunodeficiency Syndrome (AIDS)

  • Caused by HIV, leading to progressive immune dysfunction. Detection involves a combination of antibody-based tests, with treatment focusing on managing viral load to prolong latency.