Below are descriptions of biopsy or autopsy findings from four different patients. Correlate each clinical and histopathological description with its primary subcellular mechanism of injury or adaptation.
- A 72-year-old man who died of a myocardial infarction is found at autopsy to have a small, brown heart. Microscopic examination demonstrates perinuclear, yellow-brown, finely granular pigment in the myocytes.Autophagocytosis of membrane lipids and subsequent free radical-induced lipid peroxidation
- A 45-year-old woman with arthropathy and new-onset diabetes undergoes a liver biopsy, which reveals golden-yellow cytoplasmic granules that stain intensely blue with Prussian blue.Excessive gastrointestinal iron absorption leading to lysosomal accumulation of ferritin micelles
- A 65-year-old man undergoes replacement of a stenotic bicuspid aortic valve. The excised valve contains macroscopic, rigid, gritty masses. His serum calcium levels have consistently been normal.Initiation of calcium phosphate crystal formation on membrane remnants of necrotic or damaged cells
- A 50-year-old man with chronic, heavy alcohol consumption presents with hepatomegaly. Liver biopsy shows swollen hepatocytes containing tangled, ropy, eosinophilic cytoplasmic inclusions.Ubiquitination and aggregation of damaged cytokeratin intermediate filaments
Cevap
The presentations match their mechanisms as follows: The small brown heart represents lipofuscin accumulation from lipid peroxidation. The iron overload liver with Prussian blue positive granules matches hemosiderin from ferritin micelle accumulation. The calcified stenotic valve represents dystrophic calcification on necrotic debris. The alcoholic liver with eosinophilic inclusions represents Mallory-Denk bodies formed by cytokeratin intermediate filaments.
Cellular adaptation and injury often result in characteristic intracellular accumulations. Lipofuscin is a marker of past free-radical injury and lipid peroxidation, typically seen in non-dividing cells like cardiac myocytes. Hemosiderin accumulates when systemic iron overload (hemochromatosis) exceeds the storage capacity of apoferritin, leading to lysosomal accumulation of ferritin micelles. Dystrophic calcification occurs locally in damaged or necrotic tissues (such as abnormal heart valves) despite normal calcium metabolism, driven by calcium binding to membrane phospholipids. Mallory-Denk bodies are proteinopathies resulting from toxic injury (alcohol) to the hepatocyte cytoskeleton, specifically involving cytokeratin filaments.
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Anahtar Kavram
Mechanisms of intracellular accumulations and pathologic tissue calcification