It is difficult to say precisely what triggers this autoimmune disease.
Some contributing factors have been identified:
Written by Dr. France Joyal, Vascular and Internal Medicine Associate Clinical Professor University of Montreal Health Centre (CHUM)
Genetic predisposition
It is very rare to find another case of scleroderma within the same family. However, some family members may have Raynaud’s phenomenon or suffer from a collagenosis or a connective tissue disease. Rheumatoid arthritis, lupus erythmatosus, mixed connective tissue disease, Sjögren’s syndrome and scleroderma all belong to the collagenosis group. For these families, there is a genetic predisposition or susceptibility to the presence of those diseases.
Abnormal immune activity
In scleroderma, the immune system gets “confused” and begins to kill off its own cells instead of defending itself from outside threats. This self-destruction by the immune system is called “autoimmunity”. This is why scleroderma is considered an autoimmune disease.
A group of cells called fibroblasts are body cells that normally make a protein called collagen, which is important in the structure of skin, blood vessels, and other body structures. In scleroderma, these fibroblast cells are signaled to work harder than usual, making more collagen than is needed. This increased collagen causes issues such as skin thickening and other problems. This thickening is also referred to as “fibrosis”.
It is unclear whether the fibroblast cell transformation is the result of damage to small vessels that supply blood to the organs of our body, or if the blood vessels’ disease results in a fibrosis reaction around the affected organs. These two damage mechanisms are not necessarily at work in the same organ. It is not clear whether the activation related to a virus, a chemical substance or a physical attack. Environment may also be contributing to triggering a cascade reaction resulting in scleroderma. For now, the cause for this disease is not known for the majority of patients.
Autoimmune reaction primarily affects three types of cells:
- Fibroblasts whose activity is increased resulting in excessive collagen production in the skin and internal organs;
- Endothelial cells of small blood vessels (capillaries) whose destruction leads to lack of blood flow (ischemia) and dysfunction of affected organs;
- Lymphocytes, also called white blood cells, produce disease-specific auto antibodies that attack the body and contribute to the development and complications of SSc.
Diagnosis
The diagnosis of SSc is primarily based on clinical examination. If a patient does not have symptoms of skin thickening, it is difficult to make a diagnosis, as other symptoms of scleroderma are also found in many other diseases.
Raynaud’s phenomenon, which is a sign of abnormally small blood vessels, is the first clinical sign and can appear several years before any other symptoms. It is recommended that anyone having this symptom be referred to a medical specialist who will make an assessment using a variety of tests, e.g. a nailfold capillaroscopy, blood work and a skin biopsy.
Nailfold capillaroscopy consists in examining the fingertips using a microscope. It can reveal typical abnormal dilation of the small blood vessels (capillaries). Blood tests can be ordered to assess the functioning of organs and the presence of SSc-specific auto antibodies. These tests help diagnose or identify people with a high probability of suffering from this disease (Koenig, 2008).
A skin biopsy can also confirm the diagnosis by revealing, among other things, abnormal collagen deposits and thickening of the blood vessel walls.
Once the diagnosis of scleroderma is clearly established, further tests will help determine the degree of internal organ involvement. These include a chest scan, pulmonary function tests, an electrocardiogram, an echocardiogram (heart ultrasound), a radiograph of the hands and an esophago-gastro-duodenoscopy. More specifically, an esophageal manometry test or a barium swallow will assess the motility of the esophagus.
