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.

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.

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.

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.

Adult-onset Still's disease is treated with anti-inflammatory drugs. Steroids such as prednisone are used to treat severe symptoms of Still's. Other commonly used medications include hydroxychloroquine, penicillamine, azathioprine, methotrexate, etanercept, anakinra, cyclophosphamide, adalimumab, rituximab, and infliximab.

Newer drugs target interleukin-1 (IL-1), particularly IL-1β. A randomized, multicenter trial reported better outcomes in a group of 12 patients treated with anakinra than in a group of 10 patients taking other disease-modifying antirheumatic drugs. Other anti-IL1β drugs are being developed, including canakinumab and rilonacept.

The condition "juvenile-onset Still's disease" is now usually grouped under juvenile rheumatoid arthritis. However, there is some evidence that the two conditions are closely related.

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

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.

The treatment of juvenile arthritis includes medications, physical therapy, splints and in severe cases surgery. These treatments are focused on reducing swelling, relieving pain and maintaining full movement of joints. Children are encouraged to be involved in extra-curricular activities, physical activity when possible, and to live a "normal" life.

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.

Treatment with either glucocorticoids, methotrexate, anakinra, or tocilizumab has been examined. Anakinra has been shown to resolve the clinical features of the disease in 87% of patients. It also induces remission in half of corticosteroid-resistant patients. The results of another study were similar, with half of the patients responding to treatment with Anakinra. Canakinumab, an antibody to

interleukin-1 beta, is indicated for treatment in patients who respond poorly to other treatments.

25% of cases progress to severe destructive arthritis. In the United States and Canada, mortality is estimated at about 4% and in Europe, mortality is estimated at 21.7%.

In the US it affects about 250,000-294,000 children and teens making it one of the most common childhood diseases .

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.

Treatment of ALS2-related disorders includes physical therapy and occupational therapy to promote mobility and independence and use of computer technologies and devices to facilitate writing and voice communication.

Adult-onset Still's Disease is rare and has been described all over the world. The number of new cases per year is estimated to be 1.6 per 1,000,000 population. The number of people currently affected is estimated at 1.5 cases per 100,000-1,000,000 population. Onset is most common in two age ranges, between ages 15–25 and between ages of 36–46 years.

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

Inflammatory arthritis can be disabling to the point where people with the diseases can lose their jobs, which can cause psychological distress. Because it is typically progressive, those who lose their jobs are unlikely to re-enter the workforce after leaving due to their diagnosis. Programs now aim to retain those with inflammatory arthritis by preventing work-related injuries and by making necessary accommodations in the workplace. A 2014 Cochrane review found low-quality evidence that work focused interventions, including counseling, education, advocacy, and occupational medicine consultations, were effective in retaining workers with inflammatory arthritis.

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.

Inflammatory arthritis is a group of diseases which includes: rheumatoid arthritis, psoriatic arthropathy, inflammatory bowel disease, adult-onset Still's disease, scleroderma, juvenile idiopathic arthritis and systemic lupus erythematosus (SLE).

There is currently no therapy or cure for MLD in late infantile patients displaying symptoms, or for juvenile and adult onset with advanced symptoms. These patients typically receive clinical treatment focused on pain and symptom management.

Pre-symptomatic late infantile MLD patients, as well as those with juvenile or adult MLD that are either presymptomatic or displaying mild symptoms, can consider bone marrow transplantation (including stem cell transplantation), which may slow down progression of the disease in the central nervous system. However, results in the peripheral nervous system have been less dramatic, and the long-term results of these therapies have been mixed. Recent success has involved stem cells being taken from the bone marrow of children with the disorder and infecting the cells with a retro-virus, replacing the stem cells' mutated gene with the repaired gene before re-injecting it back into the patient where they multiplied. The children by the age of five were all in good condition and going to kindergarten when normally by this age, children with the disease can not even speak.

Several therapy options are currently being investigated using clinical trials primarily in late infantile patients. These therapies include gene therapy, enzyme replacement therapy (ERT), substrate reduction therapy (SRT), and potentially enzyme enhancement therapy (EET).

A team of international researchers and foundations gathered in 2008 to form an international MLD Registry to create and manage a shared repository of knowledge, including the natural history of MLD. This consortium consisted of scientific, academic and industry resources. This registry never became operational.

A painkiller available in several European countries, Flupirtine, has been suggested to possibly slow down the progress of NCL, particularly in the juvenile and late infantile forms. No trial has been officially supported in this venue, however. Currently the drug is available to NCL families either from Germany, Duke University Medical Center in Durham, North Carolina, and the Hospital for Sick Children in Toronto, Ontario.

Treatment for secondary juvenile osteoporosis focuses on treating any underlying disorder.

In late 2007, it was reported by Dr. David Pearce et al. that Cellcept, an immunosuppressant medication commonly used in bone marrow transplants, may be useful in slowing down the progress of Juvenile NCL. Fundraising is currently underway to gather the funds needed to start a clinical trial to test the safety and efficiency of CellCept for Juvenile NCL.