These are some of the disorders handled by TRS National Resource Center for Rare Disorders

English d​​escription of disorders 

​TRS Resource Centre for rare diseases is a National resource centre for several rare disorders. Here you will find an english description of the following diorders:

  • Skeletal dysplasias (including achondroplasia)
  • Arthrogryposis Multiplex Congenita (AMC)
  • Congenital Limb Deficiency
  • Ehlers-Danlos syndrome (EDS)
  • Marfan syndrome
  • Osteogenesis Imperfecta (OI)
  • Spina Bifida

Skeletal d​​ysplasia

Short stature due to skeletal dysplasia affects the skeleton. There are over 400 different subtypes of skeletal dysplasia. Skeletal dysplasia often leads to short stature or changes in body proportions, but not always.

Most skeletal dysplasias are inherited or due to a change (mutation) that may have occurred spontaneously.

The diagnosis is usually based on typical clinical findings such as short arms and legs, altered head shape or altered back shape, and skeletal findings on X-rays. Increasingly, the diagnosis can be confirmed with a genetic test.



Achondroplasia is the most common cause of short stature with skeletal abnormalities. Average final height is around 125 centimeters for women and 133 for men. Arms and legs are short compared to the rest of the body (gross disproportion).

Achondroplasia is a hereditary condition. Diagnosis is based on characteristic appearance at birth and X-rays of the skeleton. Achondroplasia can be confirmed by a genetic test where a genetic alteration is observed in the FGFR3 gene in approximately 100 percent of cases.

There are on average three to four children born with achondroplasia in Norway every year. We assume that around 100 to 150 people with the diagnosis live in Norway.

Children with achondroplasia have delayed motor development, but develop otherwise mainly as their peers. For both children and adults the small stature causes challenges when it comes to physical activity. Most are in need of practical accommodations in their daily activities. Regular medical check-ups aim to prevent complications.

Arthrogryp​​osis multiplex congenita (AMC)

Arthrogryposis multiplex congenita (AMC) describes conditions where more bent and stiff joints in different parts of the body are present at birth. Translated into English the words mean: arthro: joints, gryo: bent, multiple congenital (present at birth).

AMC is described by over 400 different conditions. In about 150 of these the cause is due to a change in the genes. AMC is divided into three subgroups: Amyoplasi, distal arthrogryposer and syndromes where AMC is part of the syndrome.

No one knows for sure how many people have AMC and the various subtypes of AMC. We assume that there are born about 10 to 12 children with AMC in Norway every year.

Congential Limb D​​eficiency

This diagnosis includes congenital conditions where the arms and/or legs are not developed normally. The condition includes defects, adhesions or a surplus of (too many) fingers or toes.

The term used in Norway is Dysmeli. In English the condition is referred to as: "congenital limb deficiency," "congenital limb anomaly", "congenital limb reduction defect/deformity", “congenital limb amputation” and "limb deficiency presented at birth".

It is not known how many people are affected, but registrations in the Medical Birth Registry show that 15 to 20 children with reduction defects are born annually in Norway.

​Ehlers-Da​​​nlos syndrome (EDS)

Ehlers-Danlos syndrome (EDS) is a group of hereditary connective tissue diseases. EDS is primarily characterized by changes in skin, being prone to tissue rupture and hyper mobile joints.

There is no single test that can detect EDS. Diagnosis is set using diagnostic criteria. An international expert group proposed in March 2017 a new EDS classification that divides the syndrome into 13 subtypes of EDS.

Which symptoms are prominent depends on the subtype of EDS. Over extendable (hypermobile) joints occur in different degrees in the various subtypes. For some of the subtypes, there may be changes in the skin - it may have increased stretchability and wider/different scars than normal. Tissue ruptures implies increased fragility in various organs for rare subtypes. 

For EDS vascular type, there is a risk of enlargement and rupture in larger blood vessels (arteries), and in internal organs such as the bowel and uterus.

Marfa​​n syndrome

Marfan syndrome is a rare and hereditary connective tissue disease. Several parts of the body may be affected: The heart and blood vessels, eyes, skeleton, lungs, skin and the hard skin around the spinal cord (dura).
The syndrome affects women and men alike.

Marfan syndrome can affect several parts of the body. Symptoms and characteristics vary from person to person, and can occur to different degrees, in different combinations and develop over time.  The heart and blood vessels have increased risk of enlargement (dilatation).

Both the arterial arteries (aorta) and other minor blood vessels (arteries) may be affected. Extension of the main pulmonary artery can cause the innermost layer of the main pulmonary artery to rupture (dissection) or the main pulmonary vein may break completely. The aortic valve, located between the left ventricle and the first part of the aorta, may begin to leak when the aorta expands. Some also have leakage in the flap between the left ventricle and the mitral valve. 

The eyes may be affected. The threads that hold the lens in the eye can move and the lens may get out of position (lens elongation). This may cause vision problems. Many with Marfan syndrome are significantly short sighted because the eyeball is often too long. Lens elastication may increase the risk of retinal retina (retinal detachment). 

Malformations in the skeleton are common. This can cause pain in muscles, tendons and joints. Many with Marfan syndrome have a narrow, thin and tall body with long fingers, arms, legs and toes - but this does not apply to everyone. Some have over extensive joints. 

Marfan syndrome increases the risk of lungs collapsing without being injured (spontaneous pneumothorax).

Osteogene​​​sis Imperfecta (OI)

OI is a group of hereditary connective tissue disorders where the main feature is changes in the skeleton (osteoporosis). Several parts of the body may also be affected: the teeth, joints, eyes, hearing and internal organs.

OI is usually caused by a lack of or weakness in the connective tissue collagen. Individuals with OI are identified as a group with increased tendency for bone fractures, over extensive and unstable joints, blue conjunctiva in the eyes, weaker tooth enamel and bones, hearing loss and short stature. Diagnosis is based on physical characteristics, x-rays and blood tests. It is possible to test to look for the genetic cause of OI.

Most have good and active lives despite medical challenges. Treatment and follow-up aims to prevent and alleviate symptoms so that the consequences for the person with OI are minimized.

Spina Bi​​fida

Spina Bifida is a congenital disorder in the development of the fetal spinal cord, the spine and the brain. Nerve tissue from the spinal cord poses through an opening in the vertebrae and forms a hernia. The consequences include paralysis and reduced sensation in the body below the spinal hernia. Congenital changes in the brain and accumulation of fluid in the brain's cavity (hydrocephalus) are common.

There is a large variation in the severity of spina bifida (spinal dysphagia). In most cases, the nerve supply in the body below the spinal cord is poorly developed. In Norway, the number of people born with spina bifida are decreasing. Medical treatment and follow-up aims to prevent complications and contribute to an active life.

​​Discription of more disorders

For a full overview of diagnoses TRS is a resource centre for, see our list of diagnoses with information in Norwegian.

What is ​​a rare disease?

​​Many different definitions are used around the world. Rare Diseases International has released a video illustrating their Operational Description of Rare Diseases. This is an internationally endorsed definition explaining what rare diseases are, and why they require particular attention.




What is TRS?

TRS is a national resource center for rare, congenital skeletal- and connective tissue disorders, Spina Bifida and limb deficiency. The users of the center are people affected by the disorders, their families, health personnel and other professionals working with this group. TRS is a part of the Norwegian National Resource Services on Rare Disorders (NKSD) and is located at Sunnaas Hospital in Nesodden, near Oslo, Norway.
Learn more about TRS
Bilde fra Sunnaas, utendørs
Last updated 4/3/2024