Chanarin-Dorfman syndrome is caused by changes (mutations) in the ABHD5 gene located on chromosome 3. This gene produces a protein involved in fat metabolism called CGI-58. This protein is called a co-factor because it helps the activity of the main enzyme, which is adipose triacylglycerol lipase (ATGL). The function of this enzyme is to break down a type of fat called triacylglycerol (TAG). This process is disturbed when either the enzyme or the helper protein doesn’t work properly. When the fat (triacylglycerol) cannot be broken down, it accumulates in various parts of the body as lipid droplets and causes different symptoms. This is what happens in a group of disorders called ‘neutral lipid storage disease’. It comprises two entities:
When the mutation occurs in the gene for the main enzyme (ATGL), the disease is called ‘neutral lipid storage disease with myopathy’.
When the mutation occurs in the gene for the helper protein (CGI-58), the disease is called ‘neutral lipid storage disease with itchthyosis’, or Chanarin-Dorfman syndrome.
It is important to distinguish between the two because the clinical presentations are very different. In the first one, patients usually present in early adulthood with muscle abnormalities caused by the accumulation of fat. In Chanarin-Dorfman syndrome, patients primarily have skin abnormalities that are apparent at birth. For this reason, Chanarin-Dorfman syndrome is also part of a group of diseases called ‘itchthyoses’, which are characterized by skin abnormalities. Another difference is the absence of heart problems (cardiomyopathy) in Chanarin-Dorfman syndrome, whereas they are present in first one.
The genetic mutation in Chanarin-Dorfman syndrome leads to abnormal accumulation of fat (lipid droplets) in many cells, especially in the skin, liver and white blood cells. The effect on the skin is an abnormal permeability, which leads to a characteristic rash and intense itching. In the liver, the lipid droplet accumulation leads to fatty change called “steatosis” that can eventually progress to cirrhosis and liver failure.
Chanarin-Dorfman syndrome is inherited in an autosomal recessive pattern, which means the individual inherits an abnormal gene from each parent. If an individual receives one normal gene and one abnormal gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the abnormal gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier, like the parents, is 50% with each pregnancy. The chance for a child to receive normal genes from both parents is 25%. The risk is the same for males and females.