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.

Despite its very similar clinical presentation to PM, IBM does not respond to the drugs that effectively treat PM, and there is no proven effective therapy for IBM. Alemtuzumab is being studied but as of May 2013 it had not demonstrated clinical effectiveness in IBM. Dysphagia (difficulty swallowing) may be improved by intravenous immunoglobulin, though more trials are needed. Non-fatiguing, systematic strength-building exercise has demonstrated benefit. Occupational and rehabilitation therapists can offer good advice on walking without falling and performing fine motor tasks, and can provide appropriate canes, braces and wheelchairs. Speech pathologists can provide advice on preventing choking episodes and reducing the anxiety of an immanent aspiration for both patients and carers.

Corticosteroids remain the main treatment modality for IOI. There is usually a dramatic response to this treatment and is often viewed as pathognomonic for this disease. Although response is usually quick, many agree that corticosteroids should be continued on a tapering basis to avoid breakthrough inflammation.

Although many respond to corticosteroid treatment alone, there are several cases in which adjuvant therapy is needed. While many alternatives are available, there is no particular well-established protocol to guide adjuvant therapy. Among the available options there is: surgery, alternative corticosteroid delivery, radiation therapy, non-steroidal anti-inflammatory drugs, cytotoxic agents (chlorambucil, cyclophosphamide), corticosteroid sparing immunosuppressants (methotrexate, cyclosporine, azathioprine), IV immune-globin, plasmapheresis, and biologic treatments (such as TNF-α inhibitors).

Radiation therapy subsequent to the injury or as a preventive measure of recurrence may be applied but its usefulness is inconclusive. If the surgery performed next step in accordance with literature postoperative single low-dose radiation with 3 weeks of oral indomethacin regimen will be preventive for recurrence.

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

Treatment is initially conservative, as some patients' calcifications will spontaneously be reabsorbed, and others will have minimal symptoms. In occasional cases, surgical debridement of the abnormal tissue is required, although success of such therapy is limited.

Treatment of myositis ossificans:

- Rest

- Reduction

- Immobilization

- Anti-inflammatory drugs

- Physiotherapy management

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.

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.

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.

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

Because different types of myopathies are caused by many different pathways, there is no single treatment for myopathy. Treatments range from treatment of the symptoms to very specific cause-targeting treatments. Drug therapy, physical therapy, bracing for support, surgery, and massage are all current treatments for a variety of myopathies.

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 is no cure or approved treatment for FOP. Attempts to surgically remove the bone result in explosive bone growth. While under anesthesia, people with FOP may encounter difficulties with intubation, restrictive pulmonary disease, and changes in the electrical conduction system of the heart. Activities that increase the risk of falling or soft tissue injury should be avoided, as even minor trauma may provoke heterotopic bone formation.

Treatment includes supportive care with analgesics and anti-inflammatory agents. Exercise should be limited as it increases pain and extends the area of infarction. Symptoms usually resolve in weeks to months, but fifty percent of sufferers will experience relapse in either leg.

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.

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.

Treatments are generally directed toward stopping the inflammation and suppressing the immune system. Typically, corticosteroids such as prednisone are used. Additionally, other immune suppression drugs, such as cyclophosphamide and others, are considered. In case of an infection, antimicrobial agents including cephalexin may be prescribed. Affected organs (such as the heart or lungs) may require specific medical treatment intended to improve their function during the active phase of the disease.

Management of neuropsychiatric lupus is similar to the management of neuropsychiatric disease in patients without lupus. Treatment depends on the underlying causes of a patient’s disease, and may include immunosuppressants, anticoagulants, and symptomatic therapy.

There is no clear form of treatment. Originally, bisphosphonates were expected to be of value after hip surgery but there has been no convincing evidence of benefit, despite having been used prophylactically.

Depending on the growth's location, orientation and severity, surgical removal may be possible.

Radiation Therapy.

Prophylactic radiation therapy for the prevention of heterotopic ossification has been employed since the 1970s. A variety of doses and techniques have been used. Generally, radiation therapy should be delivered as close as practical to the time of surgery. A dose of 7-8 Gray in a single fraction within 24–48 hours of surgery has been used successfully. Treatment volumes include the peri-articular region, and can be used for hip, knee, elbow, shoulder, jaw or in patients after spinal cord trauma.

Single dose radiation therapy is well tolerated and is cost effective, without an increase in bleeding, infection or wound healing disturbances.

Other possible treatments.

Certain antiinflammatory agents, such as indomethacin, ibuprofen and aspirin, have shown some effect in preventing recurrence of heterotopic ossification after total hip replacement.

Conservative treatments such as passive range of motion exercises or other mobilization techniques provided by physical therapists or occupational therapists may also assist in preventing HO. A review article looked at 114 adult patients retrospectively and suggested that the lower incidence of HO in patients with a very severe TBI may have been due to early intensive physical and occupational therapy in conjunction with pharmacological treatment. Another review article also recommended physiotherapy as an adjunct to pharmacological and medical treatments because passive range of motion exercises may maintain range at the joint and prevent secondary soft tissue contractures, which are often associated with joint immobility.

Clinical trials of isotretinoin, etidronate with oral corticosteroids, and perhexiline maleate have failed to demonstrate effectiveness, though the variable course of the disease and small prevalence induces uncertainty.

A handful of pharmaceutical companies focused on rare disease are currently in varying stages of investigation into different therapeutic approaches for FOP.

In August 2015, U.S. Food and Drug Administration (FDA) Office of Orphan Products Development granted La Jolla Pharmaceuticals orphan drug designation for two novel compounds for FOP. The compounds are small-molecule kinase inhibitors designed to selectively block ACVR1 (ALK2).

In August 2015, Clementia Pharmaceuticals also began the enrollment of children (ages 6 and above) into its Phase II clinical trial investigating palovarotene for the treatment of FOP. Preclinical studies demonstrated that palovarotene, a retinoic acid receptor gamma agonist, blocked abnormal bone formation in animal models via inhibition of secondary messenger systems in the BMP pathway. Clementia licensed palovarotene from Roche Pharmaceuticals, which previously evaluated the compound in more than 800 individuals including healthy volunteers and patients with chronic obstructive pulmonary disease. Palovarotene received Fast Track designation from the U.S. Food and Drug Administration (FDA) and orphan designations for the treatment of FOP from both the FDA and the European Medicines Agency (EMA).

In September 2015, Regeneron announced new insight into the mechanism of disease involving the activation of the ACVR1 receptor by activin A. In 2016, the company initiated a phase 1 study of its activin antibody, REGN 2477, in healthy volunteers; a phase 2 trial in FOP patients is planned for 2017.

Another potential therapeutic approach involves allele-specific RNA interference that targets mutated mRNA for degradation while preserving normal ACVR1 gene expression.

Further investigation into the mechanisms of heterotopic bone formation in FOP could aid in the development of treatments for other disorders involving extra-skeletal bone formation.

There is as yet inadeqaute data from randomised controlled trials.

Treatment with HAART and ACE inhibitors/Angiotensin receptor blockers has been shown to be beneficial and should be given to all patients unless otherwise contra-indicated. General renoprotective measures and the treatment of the complications of nephrotic syndrome and kidney failure are adjunctive.

Corticosteroid treatment can be useful in patients who do not respond to the above treatment. There is some evidence that ciclosporin might be helpful in selective cases, however further trials are required on both steroids and ciclosporin before these drugs can become standardised treatment if at all.

Diagnosis is fourfold: History and physical examination, elevation of creatine kinase, electromyograph (EMG) alteration, and a positive muscle biopsy.

The hallmark clinical feature of polymyositis is proximal muscle weakness, with less important findings being muscle pain and dysphagia. Cardiac and pulmonary findings will be present in approximately 25% of cases of patients with polymyositis.

Sporadic inclusion body myositis (sIBM): IBM is often confused with (misdiagnosed as) polymyositis or dermatomyositis that does not respond to treatment is likely IBM. sIBM comes on over months to years; polymyositis comes on over weeks to months. Polymyositis tends to respond well to treatment, at least initially; IBM does not.

Treatment usually involves high doses of steroids such as dexamethasone. While high doses of steroids may risk laminitis, low doses are associated with refractory cases. Antibiotics are used to treat any residual nidus of "S. equi". Non-steroidal anti-inflammatory drugs (NSAIDs), such as phenylbutazone or flunixin, may be useful to reduce fever and relieve pain. Intravenous DMSO is sometimes used as a free-radical scavenger and anti-inflammatory. Additionally, wrapping the legs may reduce edema and skin sloughing. Supportive care with oral or IV fluids may also be required.

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.

Involutional lipoatrophy is a cutaneous condition, and is an idiopathic lipoatrophy characterized clinically by non-inflammatory focal loss of fat.

Idiopathic localized involutional lipoatrophy (ILIL) is a rare and nosologically imprecise condition characterized by a focal loss of subcutaneous tissue on one or several sites, occurring without any significant triggering factor or auto-immune background, and regressing spontaneously within a few months.