Disease


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Last update: Saturday, 20 Dec 2025 at 4.36 am.


Disease: definition and clinical examples

Definition

Any deviation from or interruption of normal structure or function of a body part/organ/system, manifested by characteristic signs and symptoms, with etiology/pathology/prognosis possibly known or unknown.[1]


Disease vs health

  • Health = normal structure/function and ability to maintain homeostasis.
  • Disease = disturbance of homeostasis due to underlying abnormal process.

Core components of a disease

  1. Etiology (cause)
  2. Pathogenesis (mechanistic steps from cause → disease/how the disease develops)
  3. Pathophysiology (how normal function is disturbed/functional consequences of a disease process)
  4. Morphologic changes (structural changes, if applicable)
  5. Clinical manifestations (symptoms + signs)
  6. Outcome (recovery, chronicity, complications, death)
  • Symptom = subjective complaint (patient-reported).
  • Sign = objective finding (clinician/test).
  • Syndrome = cluster of signs/symptoms that occur together.
  • Etiology = cause of disease.
  • Pathogenesis = sequence of events from cause → disease.[2]
  • Pathophysiology = functional disturbance produced by disease.[3]

Examples

Example 1: Acute appendicitis

  • Etiology: luminal obstruction (fecalith/lymphoid hyperplasia)
  • Pathogenesis: obstruction → bacterial overgrowth → inflammation → ischemia/perforation
  • Pathophysiology: visceral pain then parietal irritation
  • Clinical: abdominal pain migration + nausea (symptoms), fever + rebound tenderness (signs)

Example 2: Type 1 diabetes mellitus

  • Etiology: autoimmune β-cell destruction (genetic + environmental triggers)
  • Pathogenesis: immune-mediated β-cell loss → insulin deficiency
  • Pathophysiology: impaired glucose uptake + increased lipolysis/ketogenesis
  • Clinical: polyuria/polydipsia/weight loss; DKA risk

Example 3: Atherosclerosis

  • Etiology: multifactorial (LDL, hypertension, smoking, diabetes)
  • Pathogenesis: endothelial dysfunction → LDL oxidation → foam cells → plaque → rupture
  • Pathophysiology: reduced perfusion + thrombosis
  • Clinical: angina, TIA/stroke, claudication

Diagram

Etiology → Pathogenesis → Pathophysiology → Symptoms/Signs → Complications/Outcome


Bibliography

  • KUMAR, Vinay; ABBAS, Abul K.; ASTER, Jon C. Robbins & Cotran Pathologic Basis of Disease. 10th edition. Philadelphia: Elsevier, 2021. ISBN 978-0-323-60992-0.
  • HALL, John E. Guyton and Hall Textbook of Medical Physiology. 14th edition. Philadelphia: Elsevier, 2020. ISBN 978-0-323-67280-1.
  • DORLAND. Dorland’s Illustrated Medical Dictionary. 32nd edition. Philadelphia: Saunders/Elsevier, 2011. ISBN 978-1-4160-6257-8.

References

  1. ↑ Incomplete citation of publication. . Dorland’s Illustrated Medical Dictionary. 32nd edition. Saunders/Elsevier, 2011. 
  2. ↑ Incomplete citation of web. Masaryk University (MUNI MED), Faculty of Medicine. [cit. 2025-12-16]. 
  3. ↑ Incomplete citation of web. Masaryk University (MUNI MED), Faculty of Medicine. [cit. 2025-12-16].