The skin disease itself is often the first sign of dermatomyositis and considered to be the main manifestation in about 40 percent of affected people [7].

Common skin findings may include: 

• Gottron's sign: Erythematous, scaly papules and plaques occurring in symmetric fashion particularly over the metacarpophalangeal joints, and interphalangeal joints 
• Heliotrope rash: Erythematous rash, with or without edema, around the eyes

Muscular signs and symptoms may occur at any time of the disease course and in some cases before the dermatologic manifestations occur. Muscular involvement usually starts as a weakness during walking, when standing, when reaching above the head, arising from a sitting position or when performing similar actions.

Some of the other symptoms associated with dermatomyositis can include:

• Cardiac manifestations (Cardiac arrhythmia, dilated cardiomyopathy)
• Contracture of joints
• Dysphagia
• Gastrointestinal ulcers and infections
• Arthralgia
• Fever
• Malaise
• Raynaud phenomenon
• Unintentional weight loss
• Pulmonary manifestations (Interstitial lung disease)

In order to diagnose dermatomyositis a person will have to go through a series of laboratory tests, electromyography, and imaging (computed tomography, ultrasonography, and chest radiography) [8]. Biopsies of the skin as well as the muscles are useful in order to confirm a diagnosis.

In older patients, there will be an assessment for malignancy once the diagnosis is confirmed. This assessment will have to be repeated on an annual basis for three years after diagnosis. In general, the testing that will be done is dependent on the patient’s age, gender, and race.

Treatment for dermatomyositis involves treatment for the muscular manifestations and the skin disease and can range from general treatments to specific treatments that will be based on each individual case [9]. There may also be associated disorders and each subsequent problem will also need individual treatments that can vary from one patient to another.

In terms of the muscle disease, corticosteroids are usually the first line of treatment. They may be used alongside an immunosuppressive agent. For the skin disease, a topical corticosteroid and an antimalarial agent is prescribed along with a recommendation to avoid sun exposure. Medications like methotrexate and mycophenolate mofetil may also be prescribed to a patient.

In some instances, surgery might be necessary. This is usually the case when a patient needs to have a calcinosis removed [10]. Calcinosis is more often found in pediatric cases of dermatomyositis and can be prevented if the disorder is treated early and continuously in children. Inpatient care at a medical facility may also be necessary for those patients who have progressive dermatomyositis.

The general prognosis is fairly good, but there is a chance to develop functional disability [6]. When this disorder affects children, contractures may develop and the occurence of generalized calcinosis may influence the prognosis.

Spontaneous remission has been seen in about 20 percent of reported cases of dermatomyositis while five percent of reported cases showed severe progression. In those more severely progressive cases, the likelihood of death related to the disorder is increased. This progression and poor prognosis is most common in patients that are over the age of 60. Patients with malignancy, cardiac problems, asthenia-anorexia or pulmonary interstitial fibrosis are also at risk for this poor prognosis.

In general, the causes of dermatomyositis are unknown. There are factors that are associated with the disorder that should be noted [2]. There are immunologic irregularities that are linked to the condition based on the fact that most patients show circulating autoantibodies. There are also polymorphisms of the tumor necrosis factors which is linked to calcinosis in children and photosensitivity in adults. With the condition there are specific genetic markers, too, which can lead to a predisposition for dermatomyositis. There is also thought to be a link between the condition and human leukocyte antigens (HLA) DR3, DR5, and DR7.

While dermatomyositis has no preference for age, there is thought to be two peak ages for the onset of the disorder. In adults, this peak age is around 50-years-old while the peak age in children is between five and 10-years-old.

Dermatomyositis is reported more often in women than men but there is no racial predilection. If looking at the numbers of cases, it is seen that there are about 9.63 instances of dermatomyositis in a pool of one million people. 

The condition itself is thought to be the result of a humoral attack on the capillaries and arterioles of the body [4]. Dermatomyositis starts after the C3 component is triggered. From there, C3b and C4b fragments form. This formation leads to the creation of C3bNE0 and the membrane attack complex. These various fragments are dropped into the endomysial vasculature along with C5b-9 MAC. This leads to endothelial cell damage, perivascular inflammation, capillary necrosis, ischemia, and destruction of muscle fibres.

At the beginning of the disease process, perifascicular atrophy is present. Then, as the condition progresses, the capillaries deteriorate and the muscles suffer from microinfarction. Necrotic and degenerative fibers will appear in later stages [5]. During the inflammation of the blood vessels, B cells and CD4 helper cells are also present. The pathophysiology of skin lesions seems to be similar. 

Preventative measures for dermatomyositis remain unclear as the etiologic factors of the condition are not known.

Affecting the skin, muscles, joints, esophagus, lungs, and even the heart, dermatomyositis is an idiopathic inflammatory myopathy that results in visible skin problems [1]. When present in children or adolescent youths, the disorder can lead to calcinosis. There is also a link to an increased risk of certain types of cancer.

Dermatomyositis is an inflammatory condition that affects both children and adults. The condition presents itself as a distinct rash that is coupled with muscle weakness. It affects women more than men and is considered to have two peak ages when it manifests. In children, dermatomyositis peaks between the ages of five and 15 while it peaks between the ages of 40 and 60 in adults.

The condition’s origins are unknown so preventative measures are also not known. It is incurable but there are treatment options available for people suffering from the disorder. These options are to treat both the muscle issues and skin issues of the dermatomyositis.