Dermatomyositis is an autoimmune muscle condition, which results in muscle weakness and rash, which are unique to this disease. It is a subtype of a larger group of diseases collectively referred to as idiopathic inflammatory myopathies (IIM). These myopathies present a generally similar pattern of weakness, but the distribution of the weakness and the histopathological findings are different. 

Dermatomyositis is characterized by muscle weakness that mainly affects the proximal muscles in the body besides skin rashes. Besides these initial signs, it can also infest other organs like the lungs, heart, and such systems in the gastrointestinal tract. A significant demography of patients with dermatomyositis present an associated malignancy which may affect the disease outcome. Although it is presented with muscle and skin manifestations, it is understood that there are various types of the disease.

Clinically amyopathic dermatomyositis (CADM) is another example of the disease, in which the person presents rash characteristic to dermatomyositis, but does not have muscle involvement. In addition, CADM has been categorized into hypomyopathic and amyopathic types. Hypomyopathic dermatomyositis patients exhibit no muscle weakness and manifest laboratory or biopsy findings of muscle inflammation. In amyopathic dermatomyositis, there is no evidence of muscle involvement clinically or in laboratory evaluation. 

Dermatomyositis is relatively rare. A cohort study from Olmsted County, Minnesota, over 1967-2007, put the incidence at 9.63 per million people within the same year. The study also indicated that out of these 21% were of the amyopathic subtype. The condition often occurs in people in their middle age, especially in their 40s and 50s with the mean age at diagnosis being about 44 years. Women are more often diagnosed than men, the incidences of 3.98 and 4.68 per million, respectively. 

In Europe, dermatomyositis is more frequent in Southern Europe than in Northern Europe. Studies showed that, especially in Canada, the condition is more common in big cities of Quebec. Moreover, the cohort study conducted in the state of Pennsylvania also proved that there were areas with a higher prevalence of CADM associated with elevated rates of air pollution.

Dermatomyositis is thought to be a humoral immune mediated disorder involving blood vessel in muscles particularly, the capillaries. The formation of C3bNEO and the C5b-C9 membrane attack complex (MAC) . It adheres to the walls of the blood vessels and leads to irritation or inflammation of blood vessels. This causes an inflammatory response around the muscle fibers which leads to hypoxic damage where the muscle fibres far from the blood supply or avascular fibres are prominent. Further, as the condition advances, both capillary density and oxygen supply to muscles reduce resulting in muscle fiber necrosis as well as degeneration. 

Genetic Factors: 

Dermatomyositis is associated with some specific HLA antigens which make some individuals more vulnerable. High-risk haplotypes include: 

HLA-DRB1*0301 in the African Americans 

In Han Chinese HLA-DRB1*07 and HLA-DQA1*0104  

DQA1*05 and HLA-DQB1*02 genes in people of the British population 

Immunologic Factors: 

Elevated antibodies are found in dermatomyositis patients, however, the exact contribution of the antibodies to the disease is not established. 

Environmental Factors: 

The viruses of Coxsackie B and enterovirus can cause dermatomyositis through various pathways including the change of proteins. 

Radiation: Another cause for dermatomyositis is chronic high intensity ultraviolet rays radiation, particularly amongst women. 

Dermatomyositis is considered to have a mortality of almost 10%, and it has been observed that the mortality is highest during the first year of the occurrence of the disease. The main medical conditions that appear to cause mortality include cancer, lung disorders, and ischemic heart disease. Risk factors that are linked to increased mortality and poorer outcomes are aged above 60 years, diagnosis made more than six months after onset of symptoms, severe muscle weakness at diagnosis, difficulty in swallowing, respiratory or cardiac involvement, and presence of malignancy. 

Among the survivors 65% have full upper limb strength, 34% has mild disability and 16% has no disability at all. About one fifth of patients recover with treatment while three fifths have either chronic illness or recurrent disease. 

Age Group: 

• Adults: Usually observed in patients aging between the 40s and the 60s. 
• Children: Although it can be diagnosed at any age, the onset of symptoms usually occurs in children between 5 to 15 years. In children, it may be characterized by such features as the joint stiffness, or contractures and calcium deposits in the skin called calcinosis. 

Skin Findings: 

• Heliotrope Rash: Periorbital erythema, the skin appearing purplish, usually on the eyelids and around the eyes accompanied by periorbital swelling. 
• Gottron’s Papules: Small nodules on the dorsum of the hand, wrists and knees especially at some joint margins. 
• Mechanic’s Hands: Coarse, scaly palms like a person who works with his or her hands. 
• Shawl Sign: Scaly erythematous lesions in the shoulder and back areas, looking like a shawl. 
• V-sign: Regarding rash, it is present in a V pattern on the chest and accompanied by a rash that may be worse in sun-exposed skin. 

Muscle Findings: 

• Proximal Muscle Weakness: When they are severely affected, proximal muscles like those in the shoulder girdle, hips and thighs will present with symmetrical weakness. This may represent in steps, lifting objects up or something like that. 
• Muscle Tenderness: Softness when touching the affected muscles, although this may be lacking in some of the patients to varying extents. 

• Malignancies: About 25% of patients are found to have an associated malignancy such as ovarian, lung, colon, and breast cancer. 
• Pulmonary Involvement: They include interstitial lung disease or respiratory muscle weakness. 
• Cardiac Issues: May include myocarditis or arrhythmias. 
• Gastrointestinal Issues: Dysphagia or esophageal involvement may occur if the tumor is in the esophagus. 
• Calcinosis: Seen more frequently in children and which is associated with less appropriate diagnostic delay or treatment. 
• Venous Thromboembolism: Higher, specifically, during periods soon after the diagnosis is made, such as in the first year. 
• Osteoporosis: Risk is higher irrespective of the corticosteroid or immunosuppressant and as before high dose of these drugs is associated with much higher risk. 

• Acute Onset: Symptoms are steadily worsening, with moderate to severe muscle weakness and skin rash developing within weeks or months. 
• Chronic or Progressive: It progresses insidiously over months to years, fair muscle strength and potential chronic disability. 

Pharmacological Therapy for Dermatomyositis: 

• Corticosteroids: First-line therapy for the management of inflammation and muscle shall weakness. 
• Immunosuppressants: when corticosteroids are ineffective or the condition has to be managed in a long-term basis. 
• Intravenous Immunoglobulin (IVIG): Useful in severe or, atopic dermatitis, resistant forms. 
• Biologics: Administered only to patients who do not benefit enough from the initial medication therapies. 
• Antimalarials: Essentially applied in the management of serious skin related eruptions. 

Physical Therapy: 

• Rehabilitation: Improve muscle mass strength, flexibility and movement patterns by using the right exercises for each client. 
• Occupational Therapy: Helps in coping with the physical changes and self-management of the tasks that encompass the daily activities. 

Management of Skin Symptoms: 

• Topical Treatments: Systemic or topical steroids for skin rashes, or tacrolimus/ mycophenolate mofetil for skin rashes. 
• Sun Protection: Protective cream/sunblock and suitable clothing to avoid worsening skin rash. 

Management of Associated Conditions: 

• Cancer Screening: To screen for the associated malignancies effectively, ethical considerations have pointed out that screening should be done regularly. 

Supportive Care: 

• Nutritional Support: Examining nutrition and eating concerns and handling of swallowing difficulties. 
• Pain Management: For use of analgesics or other treatment of muscles or joints’ pain. 

Long-Term Management: 

• Monitoring: Control re-visits to evaluate disease activity and also for side effects of the prescribed medicines. 
• Adjustment of Therapy: Treatment adjustment according to the outcome and intolerance. 

Rheumatology

• Physical Therapy: Structured programs of exercise enable one to maintain and even improve the levels of muscle strength, flexibility and functionality. These are exercising that work against weakness of the muscles and ensure that no contractures occur in the muscles. Flexibility of the joints can be enhanced by stretching exercises while range of motion while muscle strength can be maintained by strength exercising preventing muscle wastage. 
• Occupational Therapy: Helps in rehabilitation of patients and to achieve altered physical motor tasks making it easier to carry them out. Offers physical assistance in performing selected activities of daily living and offers ways of increasing patients’ levels of independence. 
• Skin Care: Sunscreens and protective clothing to avoid sun induced skin rash flare up. Use of creams in preventing dry skin and decreasing the effects of rash in cases that the skin becomes severely dry during the winter season. 
• Dietary Management: Pertains to the necessity for a proper diet to have general good health as well as for the proper functioning of muscles. Generalized feeding tips and dietary alterations to help swallowing disorders. 
• Psychosocial Support: Counselling services, which are basically aimed at making the patient mentally stable because of chronic disease. This issue can be addressed by joining other support groups so that they can feel the company of people with similar issues and find procedures to solve them from the experiences of others. 

Rheumatology

• Leflunomide: It belongs to the immunomodulatory class of drugs which works through the inhibition of pyrimidine synthesis. This action results in the antiproliferative and anti-inflammatory outcomes. 

Rheumatology

• Prednisone: This is used in the treatment process of dermatomyositis and is the only treatment known to be fully effective in the condition. It decreases capillary permeability and suppresses the release and/or function of the polymorphonuclear leukocyte. Intravenous (IV) pulses of prednisone may also be of benefit and could be associated with a reduced incidence of calcification. 
• Prednisolone: It is a corticosteroid and reduces inflammation by making capillaries less permeable and having an anti-polymorphonuclear (PMN) leukocyte effect. An evidence-based practice has previously been used to develop a practice that has been proven to enhance the symptoms of patients suffering from inflammatory myositis. 

Rheumatology

• Methotrexate: It is used to management of systemic manifestations by inhibiting the synthesis of purine bases and raising anti-inflammatory adenosine concentrations in areas of inflammation. It also aids in the reduction of symptoms associated with inflammation. 
• Azathioprine: It belongs to the group of purine analogue that interfere with purine synthesis thereby decreasing the synthesis of DNA, RNA and protein production. This results in less proliferation of immune cells and low autoimmune reactions, barely affecting the skin 
• Mycophenolate: It is commonly used to treat skin bacterial infections as well as muscle disease. It acts through competing with purines and preventing the development of lymphocyte counts. 
• Sirolimus: It prevents the stimulation of proliferation of the cells whereby it binds to such proteins as FK506 binding protein to prevent the operation of mammalian target of rapamycin. It is also approved by the Food and Drug Administration for the management of the prevention of organ rejection in patients with kidney transplant. New FDA approved cyclosporine sparing regimen enables the withdrawal of cyclosporine in patients with low to moderate rejection risk 2-4 months post-transplantation; this helps minimize renal toxicity while enhancing rejection control. 

Rheumatology

Intravenous Immune Globulin (Octagam): The patient who does not respond to the administration of corticosteroids and immunosuppressants it’s very desirable. Octagam 10% is approved by FDA for this indication in adult patients only. 

Rheumatology

• Diltiazem: It blocks the entrance of calcium ions into slow channels and voltage-sensitive segments in boilers and myocardium during depolarization. It works through an unknown pathway, yet it is off label prescribed to address calcinosis. Other calcium channel blockers have not been effective in this specific situation. 

Rheumatology

• Pamidronate: It affects bone resorption by binding to osteoclasts and their precursors with only a little influence on renal tubular calcium transport. It is given for hypercalcemia and in several instances was allegedly effective in dissolving calcinosis when given intravenously. 
• Alendronate: It is useful in reducing the discomfort that comes with Paget’s disease, although its ability to improve bone density is still under research. It is an oral medication that slows the breakdown of bones by affecting the osteoclasts and their precursors. Potential advantages of its use in the treatment of calcinosis have been established. 

Rheumatology

• Hydroxychloroquine: It may assist in attaining a measure of disease suppression or in eradicating it entirely. It is also stated that, while it is hard to compare the frequency of morbilliform drug reactions with other connective tissue diseases, it may be higher in patients with dermatomyositis. It is used in the management of inflammatory response in that it prevents chemotaxis of eosinophils, locomotion of neutrophils and complement dependent antigen-antibodies reactions. 
• Chloroquine Phosphate: It prevents the movement of eosinophils and decreases the motility of neutrophils and knocks out the complement-triggered antigen-antibody interactions. 

Rheumatology

• Skin Biopsy: This is usually done to ensure a dermatomyositis diagnosis and rule-out of other diseases that may mimic dermatomyositis. The biopsy assists in establishing characteristics skin alterations that are typical of the sickness. 
• Muscle Biopsy: Like skin biopsy, muscle biopsy should always remain an essential diagnostic tool when it comes to patients suspected to be suffering from various diseases. In inflammation, muscle fibre damage and other pathological changes that are characteristic of dermatomyositis can be detected. 
• Intravenous Immunoglobulin (IVIG): While not technically a procedure, IVIG can be an efficient treatment for dermatomyositis especially when corticosteroids will not be a practicable option. IVIG is useful in terms of immune regulation and confining inflammation. 
• Plasmapheresis: In some cases, this procedure is performed to eliminate autoantibodies from the blood; it is considered when a patient has uncontrollable severe manifestations or if he or she did not respond to other treatments. 

Rheumatology

Dermatomyositis management is done through a step wise manner. In the initial phase, therapy primarily consists of determining the severity of the acute inflammation and starting the treatment with high-dose corticosteroids and other immunosuppressive drugs. In the subacute phase, depending on the patient, further administration of treatment is carried out with supervision and new additional components such as physiotherapy to help maintain muscle tissue. In the chronic phase the goal is to sustain the disease-free state with less dose and frequency of medication, periodic visits, and PT to address the residual and recurrent symptoms and improve the patient’s quality of life. It is based on the patient’s response and progression of the disease to the subsequent phase of treatment.