Sometimes the first clue comes from the skin. Some dermatological diseases in fact represent the first symptom of the appearance of much more serious and systemic diseases of rheumatic origin. We are talking about systemic lupus erythematosus, dermatomyositis, systemic sclerosis, vasculitis and cutaneous psoriasis, which in 20% of cases is associated with psoriatic arthritis. Together with Professor Carlo Selmi, Head of Rheumatology and Clinical Immunology at Humanitas and lecturer at the University of Milan, we compared some of the main rheumatic diseases and any related dermatological symptoms.

Skin, which symptoms are related to rheumatic diseases?

Systemic lupus erythematosus

SLE is a systemic autoimmune disease and defines the category of connectivites, systemic diseases that are generally associated with anti-nuclear autoantibodies. In the expression of this complex disease, skin manifestations together with joint manifestations represent the most frequent aspects and are both included in the criteria for diagnosis. In patients with lupus, the skin can also be affected without the involvement of other organs, especially if we talk about acute, subacute and chronic skin lupus and not SLE.
Exposure to sunlight is generally sufficient to cause skin manifestations, triggering the development or re-ignition of systemic manifestations. For this reason, the patients must avoid exposure by taking photo-protection measures using physical barriers or high-protection creams. In most cases, close inter-specialist collaboration between rheumatologists and dermatologists is crucial because the histology of the lesions can be of great help in diagnosis.

Systemic sclerosis

Systemic sclerosis is a connective tissue that is often associated with scleroderma, or “hard skin” but tends to involve more organs of the body. On the endothelium of these sites of arterial circulation starts the first cause of the pathogenetic disease. For mechanisms not completely clarified, but which certainly include a constitutional predisposition, genetics, and an environmental condition, the endothelium of the people who will develop the disease is attacked and “activated”, resulting in an inflammation of the arterial walls and the passage of immune system cells from inside the bloodstream to the outside, where the immune network will determine the formation of collagen and the resulting fibrosis. For this reason we can say that the disease recognizes vascular mechanisms (well represented by the phenomenon of Raynaud), inflammatory (autoimmunity) and scarring (fibrosis as in scleroderma).

Dermatomyositis

Dermatomyositis is a rare disease that belongs to the connective tissue galaxy and how it is triggered, in predisposed patients, by an immunomediated process. Together with polymyositis, it is mainly characterized by inflammation of the muscles and, in the case of dermatomyositis, also of the skin, which is spared by polymyositis.
In addition to muscular inflammation, this disease has several signs that may appear on the skin. In 30% of patients, Gottron’s papules appear above the bony prominences, especially on the joints of the hands, elbows, knees and the inner ankle mallets. In addition, there may be a purplish-brown rash on the eyelids, with a bilateral distribution, sometimes accompanied by swelling. The so-called “shawl sign”, i.e. a dermatitis affecting the neck, forehead, shoulders and trunk areas, is also common and particularly sensitive to exposure to sunlight. Finally, psoriasis and hair loss can occur.
Another aspect which might lead to suspect a dermatomyositis, such as also in the systemic sclerosis, is the Raynaud phenomenon, that is, a variation of the color of the skin of the fingers, which first becomes white, then bluish, then red following the exposure to the cold, as well as the appearance of white-yellowish subcutaneous nodules, which usually grow on the bony prominences and are due to calcium deposits.
The possible association with neoplasms is still cause of controversy, but a possible malignant tumor is to be found, especially in the older patients, in those who are resistant to the therapy or have a relapsing disease, especially if with skin manifestations, such as an extended and atypical skin rash.

Psoriatic arthritis

Psoriasis, the skin disease that is characterized by erythematous and desquamative lesions, affects 3% of Italians and may even precede the onset of psoriatic arthropathy by several years. From an exclusively cutaneous picture there is a rheumatological involvement when you also feel joint pain, with characteristic signs of inflammation. The presence of psoriasis in some areas, particularly in the nails, increases the probability of arthritis.

Vasculitis

Vasculitis is an inflammatory process affecting the wall of veins and arteries. This family of diseases leads to narrowing or marked relaxation of the size of the vessel involved, with important repercussions in terms of spraying of organs and skin. Skin involvement may represent both the current skin manifestation of systemic vasculitis and the prevalent or exclusive skin expression variant of systemic vasculitis, but also the expression of organ-specific vasculitis with a unique and exclusive skin manifestation.
The first manifestations may or may not involve local disorders, such as pain, itching, changes in sensitivity and trophism of the tissues.