Mechanisms of Disease, Diagnosis, and Treatment

Introduction

This chapter introduces the foundational concepts of pathology, mechanisms of disease, and the principles of diagnosis and treatment. Understanding these concepts is essential for students of medical terminology, as they provide the context for the language used in clinical practice.

Pathology at First Glance

Key Definitions

• Pathology: The study of the traits, causes, and effects of abnormal conditions, causing measurable changes in structure and function.

• Homeostasis: The internal stability of the body, essential for normal function.

• Symptoms: Negative characteristics or departures from normal status, typically subjective and reported by the patient.

• Signs: Objective, abnormal findings observed by a healthcare provider.

• Syndrome: A defined collection of signs and symptoms that characterize a disorder or condition.

• Pathogenesis: The stages of development of a disease.

Types of Illness

• Acute Illness: Abrupt onset of symptoms that run a brief course.

• Chronic Illness: Disease develops slowly, can be intermittent, and lasts longer than 6 months.

Mechanisms of Disease

Systemic Health and Disruptions

• Systemic Health: Also called internal equilibrium, maintained by the coordinated function of body organs and structures.

• Major Disruptions:

  • Fluid and Electrolyte Imbalance

  • Acidosis: Too much acid, too little base, causing symptoms like fatigue and confusion.

  • Alkalosis: Too much base, too little acid, leading to muscle spasms and irritability.

Predisposing Factors

• Age

• Gender

• Lifestyle

• Environment

• Heredity

• Immunodeficiency

Changeable Predisposing Factors

• Lifestyle: Smoking, excessive drinking, risky sexual behaviors, poor nutrition, lack of exercise, psychological stressors.

• Environment: Air and water pollution, chronic psychological stress, poor living conditions, excessive noise, geographic location conducive to disease proliferation.

Non-changeable Predisposing Factors

• Age: Complications during pregnancy/postpartum, maladies associated with aging.

• Gender: Some diseases affect males and females differently.

• Heredity: Family histories of disease.

• Immunodeficiency: Risks depend on which immune system components are inadequate.

Inflammation and Repair

Acute Inflammation

• Normal protective physiologic response to tissue injury and disease.

• Accompanied by redness, heat, swelling, pain, and loss of function.

• Intensity depends on cause, area involved, and physical condition of the person.

• Attempts to wall off, destroy, and digest bacteria and dead or foreign tissue.

• Prevents spread of infection through antibody action and chemicals released by cells.

• Repair begins after insult is contained; chronic or intense inflammation can cause tissue damage.

Infection

Signs and Symptoms

• Signs: Redness, swelling, heat, pain, fever, pus, enlarged lymph glands.

• Symptoms: Fever, headache, body aches, weakness, fatigue, loss of appetite.

Sources and Transmission

• Endogenous: Originates inside the body.

• Exogenous: Originates outside the body.

• Modes of Transmission: Direct/indirect contact, inhalation, ingestion, inoculation by insect/animal.

Prevention

• Natural mechanical and chemical barriers

• Inflammatory and immune responses

• Isolation and identification of organism, immunization programs, reporting to health department

Superbugs

• Superbugs: Virulent, antibiotic-resistant strains of bacteria (e.g., MRSA, VRE, CRE).

• MRSA: Leading cause of surgical wound infections; prevented by excellent hygiene.

• VRE: Problem in chronic care facilities.

• CRE: Occurs among patients receiving treatment for other infections.

Pathogens

Genetic Diseases

Genetic Foundations

• Each cell has 23 pairs of chromosomes (X and Y are sex chromosomes).

• Each cell contains a genotype (genetic code).

• Karyotype: Ordered arrangement of photographs of a full chromosome set.

• Genes: Small stretches of DNA at specific chromosome sites.

Causes of Genetic Diseases

• Abnormality in a single gene

• Multiple abnormal genes (polygenic diseases)

• Abnormal presence/absence of entire chromosome

• Alteration in chromosome structure

• Mutations (changes in genetic code)

Modes of Inheritance

• Autosomal Dominant: Mutant phenotype seen even if normal gene is present on the other chromosome.

• Autosomal Recessive: Gene is insufficient to produce mutant phenotype in presence of normal gene on paired chromosome.

• X-linked (Sex-linked) Recessive: Gene located only on the X chromosome.

Genetic Counseling

• Communication process about the occurrence or risk of genetic disorders in a family.

• Bridges gap between medical/scientific concepts and family understanding.

• Discusses diagnosis, disease course, treatment options, and testing benefits.

• Available at most major hospitals.

Cancer

Overview

• Group of diseases with uncontrolled cell proliferation, leading to neoplasms (abnormal cell masses).

• Tumors are characterized as malignant or benign, and by cell type/tissue of origin.

Benign vs. Malignant Neoplasms

Cancer Prevention

• Diet rich in fruits, vegetables, whole grains

• Avoid tobacco smoke, excessive alcohol, and sun exposure

• Limit exposure to radiation, radon, and carcinogenic chemicals

• Increase physical activity, maintain healthy weight

• Protect against sexually transmitted infections (e.g., HPV vaccine)

Cancer Screening

• Early detection increases treatment success

• Elevation of blood serum tumor markers helps diagnosis, therapy evaluation, and recurrence screening

Stages of Cancer

• TNM Staging System:

  • T: Size and extent of primary tumor

  • N: Extent of regional lymph node involvement

  • M: Number of distant metastases

• Stage I: Best prognosis; Stage IV: Most advanced

• Other factors: Age, serum concentration, time between diagnosis and treatment

Cancer Treatment

• Surgery (curative or palliative)

• Chemotherapy (given in cycles with recovery periods)

• Hormone therapy

• Immunotherapy (stimulates body to fight cancer)

Consequences of Cancer Therapy

• Chemotherapy and radiation are toxic; predispose to other malignancies

• Children: Growth delay, cognitive impairment

• Therapies are evolving (e.g., stereotactic radiosurgery)

Cancer Vaccines

• Research ongoing for vaccines to treat existing cancer

• Approaches: Isolate cancer cell proteins to trigger immune response, or inject substances to cause generalized immune response

Immune Disorders

• Hypersensitivity Reaction (Allergy): Immune response to allergen (antigen) triggers antibody production and histamine release; can range from mild to life-threatening.

• Autoimmune Disease: Inappropriate/excessive immune response; antibodies attack self-antigens.

• Immunodeficiency Disorders: Depressed or absent immune response; causes can be primary or secondary.

Physical Trauma, Chemical Agents, and Aging

• Acute injury mechanisms require triage and precise assessment.

• Chemical agents (e.g., bioterrorism) can cause severe toxic trauma.

• Aging involves immunosenescence, increased life stresses, drug therapy issues, and changes in body composition.

Psychological Factors and Mental Disorders

• Evaluation includes observation of behavior, mood, communication, judgment, and thought processes.

• Treatment plans must be tailored; chronic disease can affect self-esteem and behavior.

• Mental disorders: Behavioral/psychological syndromes with psychic pain or functional impairment.

Diagnosis and Treatment of Disease

Diagnosis

• Medical history (patient interview)

• Physical exam (inspection, auscultation, percussion)

• Diagnostic studies (microscopic examination, chemical analysis)

Treatment

• Preventive measures

• Therapeutic procedures, medications, pain relief

• Surgery, physical therapy, diet modification, psychotherapy, patient education, follow-up care

Holistic Medicine and Cultural Diversity

• Holistic medicine considers social, emotional, intellectual, and spiritual components of the patient.

• Practitioners acknowledge patient uniqueness and encourage pursuit of highest well-being.

• Cultural diversity: Providers must overcome barriers and acquire knowledge of different cultures.

Gene Therapy and Stem Cell Research

• Gene therapy: Experimental intervention to repair/block gene expression using vectors; can be ex vivo or in vivo.

• Aims to treat autosomal or X-linked recessive diseases by adding functional gene copies.

• Stem cell research: Regenerative medicine; stem cells can differentiate or self-renew. Used in bone marrow transplants, skin/bone grafts, corneal transplants.