Six Distinct Types of Inherited Disorders Affect Several Parts of the Body

Rabbit preparing to cross the road. (Dr. Noorali Bharwani)
Rabbit preparing to cross the road. (Dr. Noorali Bharwani)

The title of this column may sound strange and you may not have heard of this condition before. That is because it is not a common problem. It is called Ehlers-Danlos syndrome (EDS). EDS is known to affect men and women of all racial and ethnic backgrounds.

EDS is a group of inherited connective tissue (bones, joints, skin) disorders, caused by various defects in the synthesis of collagen. Collagen is the main structural protein that gives strength to various connective tissues in animals. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25 to 35 per cent of the whole-body protein content.

Individuals with EDS have disorders marked by extremely loose joints, plastic like loose skin that bruises easily, brittle bones and easily damaged blood vessels. There are six distinct types of EDS currently identified. Each type is thought to involve a unique defect in connective tissue, although not all of the genes responsible for causing EDS have been found.

How common is Ehlers-Danlos syndrome? According to some literature, the exact numbers are difficult to estimate. It is believed the combined prevalence of all types of this condition may be about one in 5,000 to 40,000 individuals worldwide. There are many sub-groups of the condition that are hard to estimate.

First description of EDS was by Hippocrates in 400 B.C. In 1657 a Dutch surgeon noted a case history of a boy with very lax skin. The first association of very mobile joints to skin was published in 1892 in Moscow by A.N. Chernogubov. In 1901, Edvard Ehlers and in 1908 Henri-Alexandre Danlos described different disorders involving joints and skin with bruises. In 1936, the disorder was named Ehlers-Danlos syndrome.

Treatment is based on the symptoms. Unfortunately, there is no specific cure. Individuals with EDS generally have a normal life span. Their intelligence level is normal. Those with the rare vascular type of EDS are at greater risk of rupture of a major organ or blood vessel. These individuals have a high risk of sudden death.

What do we know about genes and mutation?

A gene is a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring. Mutation is a natural process that changes a DNA sequence. And it is more common than you may think.

As you know genetic disease is caused by an abnormality in an individual’s genetic material. The abnormality can range from minuscule to major. It occurs from a discrete mutation in a single base in the DNA of a single gene to a gross chromosome abnormality involving the addition or subtraction of an entire chromosome or set of chromosomes. Sounds complicated?

Some genetic disorders are inherited from the parents, while other genetic diseases are caused by acquired changes or mutations in a preexisting gene or group of genes. Mutations occur either randomly or due to some environmental exposure. A gene mutation is a permanent change in the DNA sequence that makes up a gene. Well, this is a short introduction to genetics.

If you have a family history of EDS and are planning to have children then you should seek genetic counseling. You can learn more about EDS from the Ehlers-Danlos National Foundation website.

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