Systemic sclerosis (SSc) is a chronic disease where the immune system, which normally protects the body from infections and disease, starts to attack the body’s own cells, causing tissue destruction. In the case of SSc it is the connective tissue, that provides the structure and support for the body (for example bones, ligaments, cartilage, tendons), which is affected.
SSc occurs when there is an over production of collagen in the skin and internal organs, such as the gastrointestinal tract, kidney, heart, and lungs. Collagen is a protein that primarily makes up fibrous connective tissue found in tendons and ligaments, in the skin and in some other organs. Symptoms result when the collagen build-up in the blood vessels of the affected organs causes inflammation, blood vessel dysfunction and scarring, making the vessels stiffer or thicker (progressive fibrosis) all of which causes the small vessels within the circulatory system to become blocked.
As a result of the damage caused to these blood vessels, complications such as pulmonary arterial hypertension (PAH) and digital ulcers (DU) can occur.
Around 40%-50% of systemic sclerosis patients suffer from Digital Ulcers, necrotic lesions located at distal digits, at least once and in 66% of cases the DUs will recur. Digital Ulcers are very painful difficult-to-heal open sores on the fingers and toes. They leave deep scars and affect the patient’s ability to perform work and daily activities effectively, particularly those associated with fingertip functions. In very severe cases, infection can become a complication, leading to bone inflammation and gangrene, for which surgery and sometimes even amputation may be required.
Endothelin (ET), a protein that regulates blood flow by restricting blood vessels is also implicated in fibrotic process which stiffen blood vessels and tissues. The resulting accumulation of connective tissue plays a key role in the underlying blood vessel damage or disease (vasculopathy), of DUs. The way in which vasculopathy occurs in DUs is similar to that of PAH, involving excessive tightening or narrowing of the vessels (vasoconstriction) and subsequently leads to the blood vessels changing shape or remodeling, often becoming smaller and more restrictive than previously. DUs are visible evidence of blood vessel damage or disease in a patient that has SSc.