Systematic Pathology: Organ-Based Disease Mechanisms
Cardiovascular and respiratory
Know the mechanisms of ischaemic heart disease (atherosclerosis, plaque rupture, thrombosis), the complications of myocardial infarction (arrhythmia, rupture, aneurysm, pericarditis), and heart failure (systolic versus diastolic). In the respiratory system, distinguish obstructive (asthma, COPD, bronchiectasis) from restrictive (fibrosis) disease; know the pathogenesis of emphysema (alpha-1 antitrypsin deficiency, protease-antiprotease imbalance) and the difference between small cell and non-small cell lung carcinoma.
Gastrointestinal and hepatobiliary
Understand peptic ulcer disease (Helicobacter pylori, NSAIDs), inflammatory bowel disease (Crohn transmural versus ulcerative colitis mucosal), and coeliac disease (gluten-sensitive enteropathy with villous atrophy). Liver disease mechanisms include steatosis, steatohepatitis, cirrhosis with portal hypertension, and hepatocellular carcinoma.
Renal and endocrine
Glomerular disease is classified as nephritic (haematuria, hypertension, oliguria) versus nephrotic (proteinuria, hypoalbuminaemia, oedema). Know the mechanisms of acute kidney injury (pre-renal, intrinsic, post-renal) and chronic kidney disease. Endocrine examples include Graves disease (TSH-receptor antibodies), Hashimoto thyroiditis, and diabetic complications.
Traps
Do not confuse nephritic and nephrotic syndromes. A normal chest radiograph does not exclude early lung disease. Cirrhosis is a final common pathway, not a single disease. Organ-specific questions often test the mechanism behind a classic association, so link the lesion to its cause.
Rule of thumb
Approach each organ question by asking: what is the primary insult, what is the histological response, and what is the clinical consequence? For example, H. pylori causes chronic gastritis, then ulceration, then risk of lymphoma or adenocarcinoma.