In 1954, Dubin and Johnson described a new clinicopathological entity consisting of chronic idiopathic jaundice with unidentified pigment in the liver in 12 cases. In the same year, Sprinz and Nelson published a report of four cases with persistent non-hemolytic hyperbilirubinemia associated with lipochrome-like pigment in the liver cells; soon the syndrome had come to be known as Dubin Johnson syndrome (DJS). This relatively rare disorder is a variety of hereditary hyperbilirubinemia and is characterized by low-grade elevation of conjugated bilirubin and no other signs of hepatic injury. It results from a mutation that leads to improper excretion of bilirubin from hepatocytes. The condition is benign, has no long-term consequences and does not require medical therapy. Diagnosing DJS is important to eliminate the possibility of other hepatobiliary disorders that may cause hepatic injury and diagnose those which may be potentially treatable.
DJS comes from mutations of the ATP binding cassette subfamily C member (ABCC2) gene. The ABCC2 gene provides instructions for producing a protein called multidrug resistance protein 2 (MRP2) that works as a transporter protein. The MRP2 protein is involved in the transport of substances out of cells and is essential for the secretion of conjugated bilirubin out of the hepatocytes into the bile duct system for excretion. Mutation of the ABCC2 gene causes a deficiency of canalicular MRP2 expression and impairs transport of conjugated bilirubin into the bile duct system. Conjugated bilirubin accumulates in hepatocytes, and conjugated bilirubin levels rise in the blood.
The liver is grossly black in appearance and on light microscopy; the architecture of the liver is normal, but there is the accumulation of dark, coarsely granular pigment in the centrilobular hepatocytes. On electron microscopy, the pigment appears to be within the lysosomes. Based upon the histochemical staining and physicochemical properties of the pigment, it appears that it is related to melanin.
Most patients with DJS are often young adults and are asymptomatic. Hyperbilirubinemia is found as an incidental finding while undergoing routine testing or being tested for some other unrelated problem. They may rarely present with mild icterus, weakness, and/or upper abdominal pain. Pruritus is not a symptom of DJS since serum total bile acid levels are normal. In women, the condition may be subclinical and discovered because of hyperbilirubinemia or obvious jaundice once started on oral contraceptives or becoming pregnant at which time development of jaundice may lead to the establishment of the diagnosis. Except for mild icterus, physical examination results are within normal limits.
Patients with DJS have hyperbilirubinemia, and it is predominantly conjugated hyperbilirubinemia. Total bilirubin concentrations are typically between 2 and 5 mg/dL but on occasion may rise to 20-25 mg/dL but this distinctly unusual. Laboratory tests including complete blood count, serum albumin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, cholesterol, and prothrombin time are normal. There is no evidence of hemolysis. Patients with DJS have a diagnostic abnormality in urinary coproporphyrin excretion, and abnormal distribution of the coproporphyrin isomers I and III in the urine is a characteristic feature of DJS. There are two naturally occurring coproporphyrin isomers, I and III. Normally about 75% of the coproporphyrin in urine is isomer III. In patients with DJS, total coproporphyrin content of the urine is normal, but >80% is isomer I. In patients with hyperbilirubinemia, studies such as the hepatobiliary iminodiacetic acid (HIDA) scan and computerized tomography (CT) of the abdomen are performed. In the patients with DJS, HIDA scan shows a characteristic pattern of delayed visualization or no visualization of the gallbladder and bile ducts in the presence of intense, homogenous, and prolonged visualization of the liver. Computed tomography scans in patients with DJS show a significantly higher attenuation than that seen in normal subjects. These studies generally are not needed or done if DJS is suspected.
Bromosulphthaleine (BSP) clearance test is no longer used in clinical practice. If done in patients with DJS, DSP clearance is normal at 45 minutes with a second (biphasic) peak occurring at 90 minutes indicating an excretory defect. The second rise is related to reflux of conjugated BSP from the liver to plasma. BSP clearance test is not specific for DJS, and similar findings may present in other cholestatic hepatobiliary disorders.
On liver biopsy in DJS, one can see the accumulation of dark, coarsely granular melanin-like pigment in centrilobular hepatocytes in a liver that otherwise looks normal. However, liver biopsy is not a recommendation for making a diagnosis.
Diagnosis of DJS can be made based on the presence of conjugated hyperbilirubinemia with no other abnormality of liver function tests and elevated urine coproporphyrin I fraction. Invasive diagnostic tests should be avoided. Genotyping of the ABCC2 gene is possible but used for scientific studies and not the clinical purpose.
DJS is a benign disease, does not progress to fibrosis or development of cirrhosis, and does not require any treatment. The importance of diagnosing DJS is to eliminate the possibility of other hepatobiliary disorders that may cause hepatic injury and diagnose those which may be potentially treatable. Phenobarbital and ursodeoxycholic acid are therapeutic for significant cholestasis that occurs in neonatal DJS.
Differential diagnosis includes:
DJS prognosis is often benign.
DJS has no risk of fibrosis progression of cirrhosis development.
Patients can receive education regarding the benign nature of DJS and that the diagnosis is important to eliminate other disorder that may lead to hepatic injury.
Dubin-Johnson syndrome is a rare and benign condition. It is essential to diagnose the disorder and to eliminate other conditions that may lead to hepatic injury. A team approach is an ideal way to limit invasive testing, proper management when needed, and correct diagnosis. When assessing for Dubin-Johnson syndrome, the patient should have the following done: