| Genetic causes of jaundice
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| There are a number of genetic disorders (Fig. 28.9) that impair bilirubin conjugation or secretion. Gilbert's syndrome, affecting up to 5% of the population, causes a mild unconjugated hyperbilirubinemia that is harmless and asymptomatic. It is due to a modest impairment in uridine diphosphate (UDP) glucuronyl transferase activity.
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| OBSTRUCTIVE LIVER DISEASE CAUSED BY PANCREATIC CANCER |
| A 65-year-old man was admitted to hospital because of jaundice. There was no abdominal pain, but he had noticed dark urine and pale stools. The gallbladder appeared palpable but not tender. Liver function tests showed: bilirubin 230 μmol/L (13.5 mg/dL), AST 32 U/L, and ALP 550 U/L. Dipstick urine testing revealed the presence of bilirubin, but no urobilin. |
| Comment. The patient had a history typical of obstructive jaundice. The increased ALP and normal AST concentrations were consistent with this, and the absence of urobilin in the urine indicated that the biliary tract was obstructed. It was important to carry out liver imaging investigations, to find the site of the obstruction; the absence of pain suggested that gallstones were not the cause. Ultrasound showed dilatation of the bile duct, and a computed tomography scan showed a mass in the head of the pancreas. At operation, cancer of the pancreas was confirmed. |
| Other inherited diseases of bilirubin metabolism are rare. Crigler-Najjar syndrome, which is the result of a complete absence or marked reduction in bilirubin conjugation, causes a severe unconjugated hyperbilirubinemia that presents at birth; when the enzyme is completely absent, the condition is fatal. The Dubin-Johnson and Rotor's syndromes impair the biliary secretion of conjugated bilirubin, and therefore cause a conjugated hyperbilirubinemia, which is usually mild.
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