The Ehlers-Danlos syndromes are classified according to their inheritance pattern. It is anticipated that the hypermobile type will be inherited in an autosomal dominant manner, as will the classical, vascular, arthrochalasia, and periodontal variants of the condition, among some others. Because the disease is inherited through autosomal dominant inheritance, just one copy of the mutated gene in each cell is required to induce the disorder. Occasionally, an affected person inherits the mutation from one of their parents who has the mutation. In other circumstances, new gene mutations cause the condition to manifest in persons who have no history of the disorder in their family.
Inherited pattern in different EDS forms
Inheritance of Ehlers-Danlos syndrome is inherited in an autosomal recessive pattern in the classical, cardiac-valvular, dermatosparaxis, kyphoscoliotic, spondylodysplastic, and musculocontractural forms. Brittle Cornea Syndrome (BSC) is inherited in an autosomal dominant manner in the classical type. A gene’s copy number is altered in each cell when it is passed down through autosomal recessive inheritance. The majority of the time, the parents of a person who has an autosomal recessive disorder are carriers of one copy of the changed gene. Still, they do not exhibit any signs or symptoms of the disease themselves.
The myopathic form of Ehlers-Danlos syndrome can be inherited in either an autosomal dominant or an autosomal recessive pattern, depending on the patient’s genetic makeup.
Ehlers-Danlos syndromes (EDS) are inherited connective tissue illnesses characterized by anomalies in collagen structure, production, and processing.
EDS was formerly classified in a different way
In order to better understand the many manifestations of Ehlers-Danlos syndrome, multiple classification systems have been developed. Initially, 11 different varieties of Ehlers-Danlos syndrome were identified by using Roman numerals to distinguish between them (type I, type II, and so on). Scientists proposed a more straightforward classification (the Villefranche nomenclature) in 1997, reducing the number of categories to six and assigning descriptive names based on their most distinguishing characteristics. In 2017, the categorization system was revised to incorporate unusual variants of Ehlers-Danlos syndrome that have just recently been discovered and classified. Ehlers-Danlos syndrome is organized into 13 kinds according to the 2017 classification.
In most kinds of Ehlers-Danlos syndrome (including the hypermobile type), a disproportionately broad range of joint movement (hypermobility) occurs, and it is a distinguishing characteristic of the hypermobile type. The development of motor abilities such as sitting, standing, and walking might be slowed in infants and toddlers with hypermobility because of their low muscle tone (hypotonia). The movable joints are unstable and prone to dislocation, which can result in chronic pain and discomfort. Infants with the arthrochalasia variety of Ehlers-Danlos syndrome are born with hypermobility in both hips and dislocations in both shoulders.
In many cases, patients who suffer from the Ehlers-Danlos syndromes have soft, velvety skin that is highly stretchable (elastic) and delicate. Individuals who are affected by this ailment tend to bruise readily, and some varieties of it can also result in aberrant scarring. Wounds that split open with minor bleeding are experienced by those who have the traditional form of Ehlers-Danlos disease and scars that spread over time to form the distinctive “cigarette paper” spots. Dermatosparaxis is a type of skin disorder that manifests as loose skin that sags and wrinkles, with additional (redundant) skin folds appearing on the face and other areas.
In the vascular variant of Ehlers-Danlos syndrome, bleeding difficulties are widespread. They are caused by the tearing (rupture) of blood arteries and organs at unpredictable times. Internal bleeding, a hole in the wall of the gut (intestinal perforation), and stroke are all possible complications of this condition. Women who have vascular Ehlers-Danlos syndrome may develop a rupture of the uterus during pregnancy. The kyphoscoliotic, classical, and classical-like varieties of Ehlers-Danlos syndrome are other Ehlers-Danlos disease types associated with blood vessel rupture.
Other kinds of Ehlers-Danlos syndrome are distinguished by the presence of additional signs and symptoms. The cardiac-valvular type is characterized by severe abnormalities with the valves that regulate blood flow through the heart. Cycloscoliotic type patients have a significant curvature of the spine that develops over time and can cause breathing difficulties due to restricted lung expansion. The thinness of the transparent covering of the eye (the cornea) and other eye abnormalities characterize brittle cornea syndrome, a kind of Ehlers-Danlos syndrome that is more common in women than men. The spondylodysplastic type is indicated by short height and skeletal abnormalities, such as abnormally curved (bowed) limbs, among other characteristics. Muscle abnormalities, such as hypotonia and chronically bent joints (contractures), are among the hallmarks of the musculocontractural and myopathic variants of Ehlers-Danlos syndrome, also known as the musculocontractural form. Abnormalities of the teeth and gums characterize the periodontal disease.
EDS is now classified in a new way
The revised categorization, which was implemented in 2017, distinguishes between 13 subtypes of EDS. Although there may be other variants of the illness, they are extremely rare and poorly understood by the medical community. It is significant to note that the indications and symptoms of EDS vary according to the type and can range from minimally loose joints to life-threatening issues. Many varieties have characteristics typical, such as hypermobility of the joints and soft, velvety skin that is highly elastic (stretchy) and prone to bruising.
Various gene mutations have been linked to EDS; however, the fundamental genetic reason in certain families has remained a mystery so far. As previously noted, the inheritance pattern of Ehlers-Danlos syndromes (EDS) differs depending on the subtype. The autosomal dominant pattern of inheritance is typically observed in arthrochalasia EDS, classical EDS, hypermobile EDS, periodontal EDS, some cases of myopathic EDS, and vascular types of EDS. Essentially, only one copy of the disease-causing gene in each cell of an individual is required for them to be harmed in order to be affected. Sometimes, a person with these types of EDS inherits the mutation from a parent who has the condition. Other cases may arise as a result of new (de novo) mutations in the gene; these cases occur in persons who do not have a family history of the disease. It is estimated that each child of a person who has autosomal dominant EDS has a 50 percent probability of acquiring the genetic mutation.
The autosomal recessive pattern of inheritance is observed in the following EDS: dermatosparaxis EDS, kyphoscoliosis EDS, classical-like EDS, cardiac-vascular EDS, brittle cornea syndrome, spondylodysplastic EDS, musculocontractural EDS, and some cases of myopathic EDS. As a result, in order to be diagnosed with any of these types of EDS, an individual must have a mutation in both alleles of the disease-causing gene present in each cell. It is common for the parents of an affected person to have one mutant copy of the gene; these persons are referred to as carriers. Typically, carriers do not exhibit any indications or symptoms of the illness. – A 25 percent (1 in 4) probability of having an autosomal recessive condition when two carriers of the condition have children, a 50 percent (1 in 2) chance of being a carrier like each of both parents, and a 25-30% chance of not having the condition and not being a carrier when the parents have children. The therapy and management are geared toward preventing significant complications and alleviating the signs and symptoms associated with the condition.
Conclusion: How are Ehlers-Danlos disorders passed down through families?
The autosomal recessive and autosomal dominant inheritance patterns for the Ehlers-Danlos syndromes are the two most well-known inheritance patterns.