Thread: Dubin-Johnson syndrome - Have A Black Liver

Dubin-Johnson syndrome - Have A Black Liver

General Info:

DBIN-JOHNSON SYNDROME

Patients with the Dubin-Johnson syndrome have a black liver, which results from the accumulation of a melanin-like pigment in lysosomes. Visualization of the gallbladder during oral cholecystography is usually delayed or absent. Urinary excretion of total coproporphyrin is normal, whereas the proportion of isomer I is higher than in normal controls (>80%). Finally, the BSP plasma retention test is normal in its initial phase, but there is a secondary rise in plasma BSP concentration at 90 minutes due to reflux of BSP from the hepatocyte to the plasma.

Dubin-Johnson syndrome (DJS) is a type of hereditary hyperbilirubinemia that was first described independently in 1954 by Dubin and Johnson and by Sprinz and Nelson.

Hereditary hyperbilirubinemias can be divided into conjugated forms and unconjugated forms. While Gilbert syndrome and Crigler-Najjar syndrome are examples of the unconjugated hyperbilirubinemias, DJS and Rotor syndrome represent the 2 types of familial conjugated hyperbilirubinemias.

Both types of conjugated hyperbilirubinemias have a relatively benign course, but establishing the diagnosis is important to spare patients from undergoing multiple unnecessary procedures and to exclude other more serious causes of hyperbilirubinemia.

Pathophysiology

DJS is an autosomal recessive disorder that is caused by a mutation in the gene responsible for the human canalicular multispecific organic anion transporter (cMOAT) protein. It is also called the multidrug resistance protein 2 (MRP2). This protein mediates ATP-dependent transport of certain organic anions across the canalicular membrane of the hepatocyte.

The human MRP2 gene has been localized to band 10q23-10q24. A defect in the cMOAT (MRP2) protein results in the impaired hepatobiliary transport of non–bile salt organic anions and is thought to be responsible for the conjugated hyperbilirubinemia and for the accumulation of hepatocellular pigment.

Several different mutations in the MRP2 gene have been identified in patients with DJS. Mutations in the ATP-binding region, which is critical for the functioning of the protein, form a significant proportion of the genetic lesions identified to date. One mutation causes impaired transcription and mislocalization of the protein.

Clinical
History

•Patients with DJS tend to develop nonpruritic jaundice during their teenaged years.

•Although most patients are asymptomatic, some patients complain of nonspecific right upper quadrant pain, which has been attributed to the anxiety associated with prolonged diagnostic testing.

•Subclinical cases can become evident during pregnancy or following the initiation of oral contraceptives.

•A thorough family history can reveal a history of jaundice in an autosomal recessive pattern.

Physical

•Aside from the presence of jaundice, physical examination findings are generally normal, with the exception of possible hepatosplenomegaly.

•Hyperbilirubinemia and clinical icterus can be worsened by intercurrent illnesses, by drugs that can decrease hepatic excretion of organic anions (eg, oral contraceptives), and by pregnancy.

----------

[HIDE]
RapidShare: Easy Filehosting
[/HIDE]

.