Once a diagnosis of JDMS is made, the treatment is often a 3-day course of Intravenous ("pulse") steroids (methylprednisolone, Solu-Medrol), followed by a high dose of oral prednisone (usually 1–2 mg/kg of body weight) for several weeks. This action usually brings the disease under control, lowering most lab tests to or near normal values. Some minor improvement in muscle symptoms may also be seen in this time, but normally it takes a long time for full muscle strength to be regained.

Once the disease process is under control, oral steroids are tapered gradually to minimize their side effects. Often, steroid-sparing drugs, such as methotrexate (a chemotherapy drug) or other DMARDs, are given to compensate for the reduction in oral steroids. Once the oral steroids are reduced to a less toxic level, the sparing agents can also be gradually withdrawn. Lab results are closely monitored during the tapering process to ensure that the disease does not recur.

In the cases where steroids or second-line drugs are not tolerated or are ineffective, there are other treatments that can be tried. These include other chemotherapy drugs, such as ciclosporin, infliximab, or other DMARDs. Another is intravenous immunoglobulin (IVIg), a blood product that has been shown to be very effective against JDMS.

To treat the skin rash, anti-malarial drugs, such as hydroxychloroquine (Plaquenil) are usually given. Topical steroid creams (hydrocortisone) may help some patients, and anti-inflammatory creams (such as tacrolimus) are proving to be very effective. Dry skin caused by the rash can be combated by regular application of sunscreen or any moisturizing cream. Most JDM patients are very sensitive to sun exposure, and sunburn may be a disease activity trigger in some, so daily application of high-SPF sunscreen is often recommended.

Of the children diagnosed with and treated for JDM, about half will recover completely. Close to 30 percent will have weakness after the disease resolves. Most children will go into remission and have their medications eliminated within two years, while others may take longer to respond or have more severe symptoms that take longer to clear up.

A common lasting effect of JDM is childhood arthritis.

There is no cure for dermatomyositis, but the symptoms can be treated. Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices, and rest. The standard treatment for dermatomyositis is a corticosteroid drug, given either in pill form or intravenously. Immunosuppressant drugs, such as azathioprine and methotrexate, may reduce inflammation in people who do not respond well to prednisone. Periodic treatment using intravenous immunoglobulin can also improve recovery. Other immunosuppressive agents used to treat the inflammation associated with dermatomyositis include cyclosporine A, cyclophosphamide, and tacrolimus. Physical therapy is usually recommended to prevent muscle atrophy and to regain muscle strength and range of motion. Many individuals with dermatomyositis may need a topical ointment, such as topical corticosteroids, for their skin disorder. They should wear a high-protection sunscreen and protective clothing. Surgery may be required to remove calcium deposits that cause nerve pain and recurrent infections.

Antimalarial medications, especially hydroxychloroquine and chloroquine, are used to treat the rashes, as they are in similar conditions.

Rituximab is used when people don't respond to other treatments.

As of 2016, treatments for amyopathic dermatomyositis in adults did not have a strong evidence base; published treatments included antimalarial medications, steroids, taken or orally or applied to the skin, calcineurin inhibitors applied to the skin, dapsone, Intravenous immunoglobulin (IVIG), methotrexate, azathioprine, and mycophenolate mofetil. None appear to be very effective but among them, IVIG has had the best outcomes.

Before the advent of modern treatments such as prednisone, intravenous immunoglobulin, plasmapheresis, chemotherapies, and other drugs, the prognosis was poor.

The cutaneous manifestations of dermatomyositis may or may not improve with therapy in parallel with the improvement of the myositis. In some people, the weakness and rash resolve together. In others, the two are not linked, with one or the other being more challenging to control. Often, cutaneous disease persists after adequate control of the muscle disease.

The risk of death from the condition is much higher if the heart or lungs are affected.

The first line treatment for polymyositis is corticosteroids. Specialized exercise therapy may supplement treatment to enhance quality of life.

Polymyositis, like dermatomyositis, strikes females with greater frequency than males.

Vitamin D/Sunlight

Omega-3 Fatty Acids

Probiotics/Microflora

Antioxidants

In severe cases of PM and DM with systemic signs, an initial three to five days on intravenous corticosteroid (methylprednisolone) may be used; but normally treatment begins with a single daily (after breakfast) high dose of oral corticosteroid (prednisone). After a month or so the strength of every second day's dose is very gradually reduced over three to four months, to minimize the negative effects of the prednisone. When a high dose of prednisone cannot be reduced without losing muscle strength, or when prednisone is effective but it is producing significant complications, "steroid sparing" oral immunosuppressants such as azathioprine, mycophenolate mofetil, methotrexate and cyclosporine, may be used in combination with reduced prednisone. Some of these steroid sparing drugs can take several months to demonstrate an effect.

To minimize side effects, patients on corticosteroids should follow a strict high-protein, low-carbohydrate, low-salt diet; and with long-term corticosteroid use a daily calcium supplement and weekly vitamin D supplement (and a weekly dose of Fosamax for postmenopausal women) should be considered.

For patients not responding to this approach there is weak evidence supporting the use of intravenous immunoglobulin, ciclosporin, tacrolimus, mycophenolate mofetil and other agents; and trials of rituximab have indicated a potential therapeutic effect.

Polymyositis and dermatomyositis are first treated with high doses of a corticosteroids

There is no current cure. The only way to treat this disease is by treating symptoms. Commonly patients are prescribed immunosuppressive drugs. Another route would be to take collagen regulation drugs.

There have been few randomized treatment trials, due to the relative rarity of inflammatory myopathies. The goal of treatment is improvement in activities of daily living and muscle strength. Suppression of immune system activity (immunosuppression) is the treatment strategy. Patients with PM or DM almost always improve to some degree in response to treatment, at least initially, and many recover fully with maintenance therapy. (If there is no initial improvement from treatment of PM or DM, the diagnosis should be carefully re-examined.) There is no proven effective therapy for IBM, and most IBM patients will need assistive devices such as a cane, a walking frame or a wheelchair. The later in life IBM arises, the more aggressive it appears to be.

Myositis is inflammation or swelling of the muscles. Injury, medicines, infection, or an immune disorder can lead to myositis. It is a documented side effect of the lipid-lowering drugs statins and fibrates.

Treatments for autoimmune disease have traditionally been immunosuppressive, anti-inflammatory, or palliative. Managing inflammation is critical in autoimmune diseases. Non-immunological therapies, such as hormone replacement in Hashimoto's thyroiditis or Type 1 diabetes mellitus treat outcomes of the autoaggressive response, thus these are palliative treatments. Dietary manipulation limits the severity of celiac disease. Steroidal or NSAID treatment limits inflammatory symptoms of many diseases. IVIG is used for CIDP and GBS. Specific immunomodulatory therapies, such as the TNFα antagonists (e.g. etanercept), the B cell depleting agent rituximab, the anti-IL-6 receptor tocilizumab and the costimulation blocker abatacept have been shown to be useful in treating RA. Some of these immunotherapies may be associated with increased risk of adverse effects, such as susceptibility to infection.

Helminthic therapy is an experimental approach that involves inoculation of the patient with specific parasitic intestinal nematodes (helminths). There are currently two closely related treatments available, inoculation with either Necator americanus, commonly known as hookworms, or Trichuris Suis Ova, commonly known as Pig Whipworm Eggs.

T cell vaccination is also being explored as a possible future therapy for autoimmune disorders.

There is no standard course of treatment to slow or stop the progression of the disease. sIBM patients do not reliably respond to the anti-inflammatory, immunosuppressant, or immunomodulatory medications. Management is symptomatic. Prevention of falls is an important consideration. Specialized exercise therapy may supplement treatment to enhance quality of life. Physical therapy is recommended to teach the patient a home exercise program, to teach how to compensate during mobility-gait training with an assistive device, transfers and bed mobility.

When sIBM was originally described, the major feature noted was muscle inflammation. Two other disorders were also known to display muscle inflammation, and sIBM was classified along with them. They are dermatomyositis (DM) and polymyositis (PM) and all three illnesses were called idiopathic (of unknown origin) myositis or inflammatory myopathies.

It appears that sIBM and polymyositis share some features, especially the initial sequence of immune system activation, however, polmyositis comes on over weeks or months, does not display the subsequent muscle degeneration and protein abnormalities as seen in IBM, and as well, polymyositis tends to respond well to treatments, IBM does not. IBM is often confused with (misdiagnosed as) polymyositis. Polymyositis that does not respond to treatment is likely IBM.

Dermatomyositis shares a number of similar physical symptoms and histopathological traits as polymyositis, but exhibits a skin rash not seen in polymyositis or sIBM. It may have different root causes unrelated to either polymyositis or sIBM.

Unfortunately, treatment for the anti-synthetase syndrome is limited, and usually involves immunosuppressive drugs such as glucocorticoids. For patients with pulmonary involvement, the most serious complication of this syndrome is pulmonary fibrosis and subsequent pulmonary hypertension.

Additional treatment with azathioprine and/or methotrexate may be required in advanced cases.

Prognosis is largely determined by the extent of pulmonary damage.

Adenocarcinoma of the bowel has been associated with coeliac disease.

Dermatopolymyositis (also called PM/DM) is a family of myositis disorders that includes polymyositis and dermatomyositis.

Scleromyositis or the PM/Scl overlap syndrome is a complex autoimmune disease (a disease in which the immune system attacks the body). Patients with scleromyositis have symptoms of both systemic scleroderma and either polymyositis or dermatomyositis, and is therefore considered an overlap syndrome. Although it is a rare disease, it is one of the more common overlap syndromes seen in scleroderma patients, together with MCTD and Antisynthetase syndrome. Autoantibodies often found in these patients are the anti-PM/Scl (anti-exosome) antibodies.

The symptoms that are seen most often are typical symptoms of the individual autoimmune diseases and include Raynaud's phenomenon, arthritis, myositis and scleroderma. Treatment of these patients is therefore strongly dependent on the exact symptoms with which a patient reports to a physician and is similar to treatment for the individual autoimmune disease, often involving either immunosuppressive or immunomodulating drugs.

- Clinical characteristics:

- Overlap Syndrome: scleroderma overlap syndrome

- Autoimmune disease

- Scleroderma myositis overlap syndrome

Fibromyalgia was found in 9% of adult patients relative to 0.03% in the general population with a link common to IBD. Concurrent IBS is found in 30% to 70%. Small intestinal bacterial overgrowth is associated is common with a transient response to antimicrobial therapy.

These are also referred to as systemic autoimmune diseases. The autoimmune CTDs may have both genetic and environmental causes. Genetic factors may create a predisposition towards developing these autoimmune diseases. They are characterized as a group by the presence of spontaneous overactivity of the immune system that results in the production of extra antibodies into the circulation. The classic collagen vascular diseases have a "classic" presentation with typical findings that doctors can recognize during an examination. Each also has "classic" blood test abnormalities and abnormal antibody patterns. However, each of these diseases can evolve slowly or rapidly from very subtle abnormalities before demonstrating the classic features that help in the diagnosis. The classic collagen vascular diseases include:

- Systemic lupus erythematosus (SLE) – An inflammation of the connective tissues, SLE can afflict every organ system. It is up to nine times more common in women than men and strikes black women three times as often as white women. The condition is aggravated by sunlight.

- Rheumatoid arthritis – Rheumatoid arthritis is a systemic disorder in which immune cells attack and inflame the membrane around joints. It also can affect the heart, lungs, and eyes. Of the estimated 2.1 million Americans with rheumatoid arthritis, approximately 1.5 million (71 percent) are women.

- Scleroderma – an activation of immune cells that produces scar tissue in the skin, internal organs, and small blood vessels. It affects women three times more often than men overall, but increases to a rate 15 times greater for women during childbearing years, and appears to be more common among black women.

- Sjögren's syndrome – also called Sjögren's disease, is a chronic, slowly progressing inability to secrete saliva and tears. It can occur alone or with rheumatoid arthritis, scleroderma, or systemic lupus erythematosus. Nine out of 10 cases occur in women, most often at or around mid-life.

- Mixed connective tissue disease – Mixed connective-tissue disease (MCTD) is a disorder in which features of various connective-tissue diseases (CTDs) such as systemic lupus erythematosus (SLE); systemic sclerosis (SSc); dermatomyositis (DM); polymyositis (PM); anti-synthetase syndrome; and, occasionally, Sjögren syndrome can coexist and overlap. The course of the disease is chronic and usually milder than other CTDs. In most cases, MCTD is considered an intermediate stage of a disease that eventually becomes either SLE or Scleroderma.

- Undifferentiated connective tissue disease (UCTD) is a disease in which the body mistakenly attacks its own tissues. It is diagnosed when there is evidence of an existing autoimmune condition which does not meet the criteria for any specific autoimmune disease, such as systemic lupus erythematosus or scleroderma. Latent lupus and incomplete lupus are alternative terms that have been used to describe this condition.

- Psoriatic arthritis is also a collagen vascular disease.

A connective tissue disease is any disease that has the connective tissues of the body as a target of pathology. Connective tissue is any type of biological tissue with an extensive extracellular matrix that supports, binds together, and protects organs. These tissues form a framework, or matrix, for the body, and are composed of two major structural protein molecules: collagen and elastin. There are many different types of collagen protein in each of the body's tissues. Elastin has the capability of stretching and returning to its original length—like a spring or rubber band. Elastin is the major component of ligaments (tissues that attach bone to bone) and skin. In patients with connective tissue disease, it is common for collagen and elastin to become injured by inflammation (ICT). Many connective tissue diseases feature abnormal immune system activity with inflammation in tissues as a result of an immune system that is directed against one's own body tissues (autoimmunity).

Diseases in which inflammation or weakness of collagen tends to occur are also referred to as collagen diseases. Collagen vascular diseases can be (but are not necessarily) associated with collagen and blood vessel abnormalities and that are autoimmune in nature. See also vasculitis.

Connective tissue diseases can have strong or weak inheritance risks, and can also be caused by environmental factors.

The prognosis of mixed connective tissue disease is in one third of cases worse than that of systemic lupus erythematosus (SLE). In spite of prednisone treatment, this disease is progressive and may in many cases evolve into a progressive systemic sclerosis (PSS), also referred to as diffuse cutaneous systemic scleroderma (dcSSc) which has a poor outcome. In some cases though the disease is mild and may only need aspirin as a treatment and may go into remission where no Anti-U1-RNP antibodies are detected, but that is rare or within 30% of cases. Most deaths from MCTD are due to heart failure caused by pulmonary arterial hypertension (PAH).

An overlap syndrome is an autoimmune disease of connective tissue in which a person presents with symptoms of two or more diseases.

Examples of overlap syndromes include mixed connective tissue disease and scleromyositis. Diagnosis depends on which diseases the patient shows symptoms and has positive antibodies for in their lab serology.

In overlap syndrome, features of the following diseases are found (most common listed):

- Systemic lupus erythematosus (SLE),

- Systemic sclerosis,

- Polymyositis,

- Dermatomyositis,

- Rheumatoid arthritis (RA)

- Sjögren's syndrome

- Eosinophilic granulomatosis with polyangiitis (EGPA)

- Autoimmune thyroiditis

- Antiphospholipid antibody syndrome

The treatment of overlap syndrome is mainly based on the use of corticosteroids and immunosuppressants. Biologic drugs, i.e. anti-TNFα or anti-CD20 monoclonal antibodies, have been recently introduced as alternative treatments in refractory cases. There are some concerns with the use of anti-TNF agents in patients with systemic autoimmune diseases due to the risk of triggering disease exacerbations.

Anti-synthetase syndrome is a autoimmune disease associated with interstitial lung disease, dermatomyositis, and polymyositis.