Cytoband (human 10q24.2 ABCC2) & (mouse 19qC3 Abcc2).
Here I present: “Dubin-Johnson Syndrome“, Victor McKusick, Mendelian Inheritance in Man’, 1966. (ABCC2) icd10=E80.6
INTRODUCTION.
Dubin-Johnson syndrome (DJS) is an autosomal recessive disorder characterized by conjugated hyperbilirubinemia, an increase in the urinary excretion of coproporphyrin isomer I, deposition of melanin-like pigment in hepatocytes, and prolonged retention of sulfobromophthalein, but otherwise normal liver function
Dubin–Johnson syndrome (DJS) is a benign inherited liver disorder that causes chronic conjugated (direct) hyperbilirubinemia.
Core features
Inheritance: Autosomal recessive
Gene: ABCC2 → defective MRP2 transporter. ABCC2 is ATP-binding cassette (canalicular) transporter-2
Problem: Liver can conjugate bilirubin normally, but cannot excrete it efficiently into bile.
Result: Conjugated bilirubin backs up into blood.
Hallmark Signs
Mild, lifelong jaundice (often noticed in adolescence)
Usually no liver failure and normal life expectancy
Liver enzymes usually normal
Darkly pigmented liver (“black liver”) on biopsy due to melanin-like pigment.
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Here is a clear clinical comparison of the three classic benign hyperbilirubinemias:
Dubin–Johnson vs Rotor vs Gilbert Syndromes.
Dubin–Johnson: “Direct bilirubin, Dark liver.”
Rotor: “Direct bilirubin, Regular-colored liver.”
Gilbert: “Glucuronyl transferase gives up.”
Quick Diagnostic Clue.
If conjugated bilirubin is high and liver is black → Dubin–Johnson
If conjugated bilirubin is high and liver looks normal → Rotor Syndrome
If unconjugated bilirubin is high → Gilbert Syndrome
There is evidence that Dubin-Johnson syndrome is caused by mutation in th ATP-binding cassette (canalicular) transporter-2 (ABCC2) gene encoded on genomic coordinate 10:99,782,640 and 10q24.2 cytoband in humans.
