Hepatitis D

Synonyms in the broadest sense

inflammation of the liver, inflammation of liver parenchyma, viral hepatitis, autoimmune hepatitis, toxic hepatitis

Definition

Hepatitis D is an inflammation of the liver caused by the hepatitis D virus (also: hepatitis delta virus, HDV, formerly known as delta agent). However, this is only possible if an infection with the hepatitis B virus has occurred either simultaneously or previously. 5% of patients permanently infected with hepatitis B are co-infected with the hepatitis D virus.

The Hepatitis D Virus

The hepatitis D virus (HDV) belongs to a very rare type of virus. It is an incomplete (“naked”) virus, which is also called a virusoid. Its special feature is the lack of a virus envelope, which is needed to dock to foreign cells and to introduce the virus into the host cell.

Therefore, HDV uses the hepatitis B virus (HBV) as a helper. Thus, the hepatitis D virus is only able to multiply in the presence of the hepatitis B virus. It binds to proteins in the envelope of the HBV called HBsAg and thus uses the same infection pathway as the hepatitis B virus.

Once the HDV has injected its genetic material (RNA = ribonucleic acid) into the host cell, this cell incorporates the foreign RNA into its own metabolism and now produces the virus’ proteins. Once the individual components of the virus have been formed, they assemble and the new virus leaves the cell, which is then destroyed. Thus, HDV, which does not have its own metabolism, multiplies.

There are 3 different genotypes of HDV, i.e. 3 different types of RNA. In certain areas of the world, such as the Mediterranean, Romania, the Middle East, Africa or the Amazon region, so-called hepatitis D endemics occur at times. An endemic disease is the permanent accumulation of a disease in a certain region. The sporadic occurrence of hepatitis D is found on all continents, especially within the hepatitis B risk groups, i.e. drug addicts (intravenous drugs), sex tourists, hetero- and homosexuals with frequently changing sexual partners, recipients of blood preserves, dialysis patients, medical personnel, etc.

  • Genotype I is found in the western world, Taiwan and Lebanon.
  • Genotype II is common in East Asia and
  • Genotype III in South America.