Metabolic diseases of the liver

Transcription

1 Metabolic diseases of the liver Central role in metabolism Causes and mechanisms of dysfunction Clinical patterns of metabolic disease Clinical approach to problem-solving Specific disorders

2 Liver s central role in metabolism Pathways involve CHO, protein, lipid, trace element and vitamin metabolism Synthesis e.g. serum proteins Detoxification/degradation e.g. ammonia Regulation e..g. blood glucose

3 Metabolic function of the liver Reactions disturbed by Congenital deficiency of enzymes Nutritional deficiency/excess of substrate Toxic/chemical damage to organelles Hypoxic/ischaemic insult Secondary to metabolic effects of disease

4 Metabolic disorders of amino acid metabolism of bile acid synthesis and metabolism of carbohydrate metabolism of bile flow and excretion of mitochondrial function of peroxisomal function of copper metabolism

5 Metabolic dysfunction : inherited disease Essential product deficit e.g. G-6-P deficiency (Glycogen storage I) Precursor accumulation e.g. OTC deficiency (Hyperammonaemia) Alternative pathway activation e.g. Aminoacidopathy Combinations of above

6 Mitochondrial damage Inhibition of beta oxygenation of fatty acids leads to microvesicular steatosis Interference with oxidative phosphorylation leads to insufficient ATP generation Impairment of the respiratory chain leads to excess ROS with lipid peroxidation Increase in permeability transition leads to cell death (apoptosis)

7 Mitochondrial dysfunction Inborn enzyme deficiencies involving: fatty acid oxygenation organic acids lactate metabolism oxidative phosphorylation urea cycle Episodic decompensation precipitated by intercurrent stress

8 Toxic damage to liver Mitochondrial damage Drugs (antivirals, salicylate, valproate, tetracycline) Toxins (hypoglycin, atractyloside) Endothelial damage to hepatic veins Drugs (cytotoxic drugs) Toxins (Senecio, aflatoxin, pyrrolizidine) Glutathione depletion and cell death Drugs (paracetamol) Hypoxic ischaemia

9 Mechanisms of centrilobular necrosis Sepsis Shock induced ischaemia Congestive heart failure Toxicity from drugs and poisons made worse by Malnutrition Infection Fasting Exercise

10 Pathologic manifestations of metabolic disease of the liver No structural abnormalities evident but severe functional disturbance Hepatocyte injury leading to apoptosis, necrosis, cirrhosis or tumours Storage of lipid, glycogen or other products manifesting as hepatomegaly

11 Clinical patterns of metabolic disease involving the liver Newborn acute metabolic crisis mimics sepsis Severe vomiting and failure to thrive Recurrent episodes of vomiting and encephalopathy with acidosis Progressive retardation or seizures with hepatomegaly Hepatomegaly with/without jaundice and failure to thrive/grow normally

12 Inherited metabolic disease presenting with acute onset liver failure Reye-like Typical age Neonatal to 3 years Past history Episodic vomiting since neonatal period, possible failure to thrive, possible family history Preceding history Abnormal stress such as infection, fasting, exercise Clinical features Progressive encephalopathy and anicteric multisystem failure and acidosis

13 Inherited metabolic disease presenting with acute onset liver failure Reye-like Typical biochemical findings Functional disturbance Pathology Treatment Hypoglycaemia. Ketosis often absent. Metabolic acidosis. Transaminases elevated. Hyperammonaemia. Prolonged prothrombin time. Decreased serum albumin. Leucocytosis. Raised acute phase reactants. Mitochondrial dysfunction Microvesicular steatosis Supportive for liver failure : attend to hypoglycaemia, acidosis, bleeding tendency, hyperammonaemia.