Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (203 page)

NONPHYSIOLOGIC JAUNDICE

Cause should be sought for underlying pathologic jaundice if

   Total serum bilirubin >7 mg/dL during the first 24 hours or increases >5 mg/ dL/day or visible jaundice

   Peak total serum bilirubin >12.5 mg/dL in white or black full-term infants or >15 mg/dL in Hispanic or premature infants

   Conjugated serum bilirubin >1.5 mg/dL

HEREDITARY AND/OR CONGENITAL CAUSES OF UNCONJUGATED HYPERBILIRUBINEMIA

CRIGLER-NAJJAR SYNDROME (HEREDITARY GLUCURONYL TRANSFERASE DEFICIENCY)

   A rare familial autosomal recessive disease due to marked congenital deficiency or absence of glucuronyl transferase, which conjugates bilirubin to bilirubin glucuronide in hepatic cells (counterpart is the homozygous Gunn rat)

   Laboratory Findings

   See Table
5-14
.

Type I

Histology
: Liver biopsy is normal.

Core laboratory
: Unconjugated serum bilirubin is increased; it appears on the 1st or 2nd day of life, rises in 1 week to peak of 12–45 mg/dL and persists for life. No conjugated bilirubin in serum or urine. Liver function tests are normal; BSP is normal. Fecal urobilinogen is very low.

   Other Considerations

   Untreated patients often die of kernicterus by age 18 months.

   Nonjaundiced parents have diminished capacity to form glucuronide conjugates with menthol, salicylates, and tetrahydrocortisone.

   Type I should always be ruled out when there are persistent unconjugated bilirubin levels of 20 mg/dL after 1 week of age without obvious hemolysis and especially after breast milk jaundice has been ruled out.

GILBERT DISEASE

   Chronic, benign, intermittent, familial (autosomal dominant with incomplete penetrance), nonhemolytic unconjugated hyperbilirubinemia with evanescent increases of unconjugated serum bilirubin, which is usually discovered on routine laboratory examinations; due to defective transport and conjugation of unconjugated bilirubin.

   Jaundice is usually accentuated by pregnancy, fever, exercise, and various drugs, including alcohol and birth control pills.