Pathology: Mechanisms of Disease and Injury Patterns
Pathology questions test whether you can move from a mechanism to a morphological consequence. Organise your revision around the core processes: cell injury and necrosis versus apoptosis, acute and chronic inflammation, repair and fibrosis, haemodynamic disorders (thrombosis, embolism, infarction, oedema), neoplasia and its grading and staging, and genetic and immunological disease. For each, know the defining feature and the clinical translation. Coagulative necrosis follows ischaemia in most solid organs; liquefactive necrosis follows cerebral infarction and abscess formation; caseous necrosis is associated with tuberculosis; fat necrosis follows pancreatic injury.
In haemodynamics, be precise about Virchow's triad: endothelial injury, abnormal blood flow and hypercoagulability. In inflammation, distinguish the vascular phase from the cellular phase, and know that neutrophil predominance suggests acute processes while lymphocytes and macrophages suggest chronic ones.
Traps appear when a question offers a familiar disease name but asks about the underlying process, or when it conflates grading (differentiation) with staging (spread).
Worked example
A patient with a long bone fracture becomes breathless and hypoxic; the stem asks for the pathological process. Fat embolism follows mechanical release of marrow fat into the venous circulation, lodging in pulmonary capillaries. The rule of thumb is to name the embolic material and its route before naming a clinical syndrome: venous thromboembolism travels to the lungs, arterial embolism travels to systemic beds, and paradoxical embolism requires a right-to-left shunt.