Idiopathic inflammatory myopathies (IIMs) are a group of autoimmune diseases characterized by myositis and potentially affecting other organs. The conditions can cause an expose organ failure, enhanced morbidity and early mortality among patients. The definition of IIMs has greatly evolved since the publication of the Bohan and Peter criteria in 1975, mainly due to improvements in identifying clinical features and available therapies. The four major subcategories are dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myopathy (NAM), and sporadic inclusion body myositis (sIBM). They typically manifest sub-acute to chronic proximal muscle weakness, which affects activities of daily living such as getting up from a chair, climbing stairs, lifting objects, or combing the hair. Diagnostic evaluation usually includes laboratory tests, which reveal increased serum creatine kinase (CK) and the presence of myositis-specific autoantibodies (MSA), which would allow differentiating among the clinical phenotypes and establishing the diagnosis. 

They are not very frequent diseases, with an overall incidence rate of 11 per million years of exposure to the population (10 for males and 13 for females) and a prevalence of 14 per 100,000 inhabitants. These inflammatory involvement of the musculoskeletal system muscle disorders occur more commonly in adults between the ages of 45 to 60 years, while in children, between the age of 5 to 15 years. Specifically, IBM is more frequent in males and has a male predominance with a ratio of 2:1, while other IIM subtypes are prevalent in women. 

The pathophysiology of idiopathic inflammatory myopathies (IIMs), is an autoimmune mediated response that targets muscle tissue, causing inflammation and damage to athletes. T-cells and macrophagés enter the muscle tissue of the muscle fibers. This process varies among the different IIM subtypes: Polymyositis is associated with endomysial inflammation that is rich in CD8 + T-cells, dermatomyositis presents perimysial inflammation and rash as signs, inclusion body myositis presents rimmed vacuoles and mixed inflammation and necrotizing autoimmune myopathy presents extensive muscle fiber necrosis with associated minor inflammation. Due to chronic inflammation the muscle regeneration process is impaired, and fibrosis is enhanced and consequently more muscle weakness and in some cases involvement of the internal organs is developed. 

Viral infections have been suggested as potential triggers for IIMs. Some studies have proposed that infections may initiate or exacerbate the inflammatory process in susceptible individuals. 

Chronic muscle injury or stress might contribute to the onset of IIMs by provoking an inflammatory response. 

The prognosis of idiopathic inflammatory myopathies (IIMs) depends on different factors as mentioned below. There are various subtypes of the disease which are Dermatomyositis (DM), Polymyositis (PM), Inclusion Body Myositis (IBM), and Necrotizing Autoimmune Myopathy (NAM). Patients with isolated DM have a relatively better prognosis if their condition is not associated with cancer. IBM patients are distinguished by a later age of onset and are characterized by a shorter life expectancy and more severe clinical course. In patients who do not receive treatment early or who delay it until the disease has advanced, the prognosis is usually unfavorable. It has been demonstrated that the level of muscle weakness at time of diagnosis and the rate of progression of this process can affect outcomes. Extramuscular manifestations and systemic involvement which can make the disease course more severe and unfavorable. 

Age Group and Clinical Presentation: 

• Children (5 to 15 years): Commonly present with dermatomyositis, featuring muscle weakness, characteristic rashes (heliotrope rash, Gottron’s papules), and systemic symptoms.  
• Adults (45 to 60 years): Common types include polymyositis and dermatomyositis, with proximal muscle weakness (difficulty with tasks like climbing stairs and lifting objects), potential skin rashes, and systemic symptoms.  
• Older Adults (≥60 years): Primarily experience inclusion body myositis (IBM), marked by progressive muscle weakness affecting both proximal and distal muscles. Symptoms usually develop gradually over months to years. 

Muscle Strength 

Dermatological Signs 

Muscle Atrophy 

Systemic Examination 

Reflexes and Sensory Exam 

Malignancies: 

Infections 

Statin Use 

• Sub-acute to Chronic: Polymyositis and dermatomyositis typically present with gradual muscle weakness over weeks to months, with potential for acute flare-ups. 
• Acute: Dermatomyositis, especially in children, may present with a rapid onset of muscle weakness and rash. 
• Insidious: Inclusion Body Myositis (IBM) usually has a gradual onset with slow progression of symptoms. 

Pharmacological Therapy: 

• Corticosteroids: First-line treatment for most IIMs. Prednisone is commonly used to reduce inflammation and improve muscle strength. The dose is usually tapered based on response. 
• Immunosuppressants: Used if corticosteroids alone are insufficient or if long-term corticosteroid use needs to be minimized. Options include: 
• Methotrexate: Often used as a steroid-sparing agent. 
• Azathioprine: Another steroid-sparing agent. 
• Biologics: Considered for cases resistant to traditional therapies. Rituximab (anti-CD20 monoclonal antibody) and intravenous immunoglobulin (IVIG) are options for refractory cases or specific subtypes like DM. 
• Intravenous immunoglobulin (IVIG): Used particularly in dermatomyositis and sometimes in inclusion body myositis. 

Non-Pharmacological Therapy: 

• Physical Therapy: Essential for improving muscle strength, function, and overall physical conditioning. A tailored exercise program can help maintain mobility and prevent contractures. 
• Occupational Therapy: Helps patients adapt to physical limitations and improve daily functioning. 

Management of Complications: 

• Swallowing Therapy: For patients with dysphagia, especially in IBM. 
• Pulmonary Management: Monitoring and managing respiratory issues, which may arise in advanced cases or in dermatomyositis with associated interstitial lung disease. 
• Monitoring and Follow-Up: To assess disease activity, treatment response, and monitor for side effects. This includes clinical assessments, muscle strength evaluations, and relevant laboratory tests (e.g., muscle enzymes, autoantibodies). 

Rheumatology

• Physical Therapy: Essential for improving muscle strength, function, and overall physical conditioning. A tailored exercise program can help maintain mobility and prevent contractures. 
• Occupational Therapy: Helps patients adapt to physical limitations and improve daily functioning. 

Rheumatology

• Prednisone: This is a powerful anti-inflammatory/ immunosuppressive drug which has a therapeutic function for auto-immune diseases. It also can minimize inflammation since it interacts with increased capillary permeability and promotes neutralization of neutrophils. Also, it has properties of the stabilisation of the lysosomal membranes and inhibits the activity of lymphocytes that consequently reduces the formation of cytokines and antibodies. 
• Corticotropin: It is obtained from porcine ACTH and increases the synthesis of adrenocortical hormones. 

Rheumatology

• Methotrexate: Its exact way of working in the treatment of chronic inflammatory diseases is unknown but may affect the function of immune system through suppression of the production of cytokines that are pro-inflammatory in nature. It also relives some conditions that are associated with the joint such as pain, swelling and stiffness. Dosage should be titrated in a stepwise motion to get the appropriate therapeutic effect. 
• Azathioprine: It is a purine analog which exerts an antineoplastic effect by competing with the normal purines in synthesizing the DNA, RNA and proteins. This action leads to a decline in the number of immune cells thus decreasing the general activity of the Immune system.
• IV Immunoglobulin: IVIG mechanisms include the binding, where anti-idiotypic antibodies in IVIG bind to the circulating myelin antibodies thus, inactivating them. It inhibits the elaboration of a variety of cytokines such as Interferon-G; it blocks Fc receptors on macrophages; it suppresses the proliferation of helper T and B lymphocytes; and it stimulates suppressor T lymphocyte activity. The precise method by which IVIG is effective in yielding polymyositis is still an issue of debate.
• Cyclophosphamide: It belongs to nitrogen mustards and alkylating agents, with actions of its active metabolites involving DNA cross-linking. This cross-linking limits the proliferation of both normal cells including the lymphocytes as well as the cancerous cell. 

Rheumatology

• Etanercept: It particularly works on tumor necrosis factor (TNF) and prevents TNF from attaching to the TNF receptors which are present on the cell surface, thus neutralizing the TNF. 
• Infliximab: It acts as a dimeric protein that can recognize both TNF-alpha in solution and the membrane bound form, thus, exerting an inhibitory effect on the cytokine. 

Rheumatology

Rituximab: This is a humanized monoclonal antibody which works by binding itself to the CD20 antigen, which is present on the surface of B cells, thereby causing the activation of the complement or antibodies which in turn destroys the targets. Clinical trials have also proven that Idiopathic Inflammatory Myopathies are effective in managing polymyositis patients who had not followed the corticosteroid and immunosuppressant regimen. 

Rheumatology

Diltiazem: They observed that diltiazem inhibits the influx of calcium ions in slow channels and voltage sensitive parts of the vascular smooth muscles and the myocardial cells during depolarisation. Diltiazem is approved for certain cardiac diseases but can be prescribed for calcinosis, however, its role in this connection is not very clear fully. Other calcium channel blockers have not been used to manage this condition, according to the available literature. 

Rheumatology

Physical Therapy and Rehabilitation: 

• Exercise Therapy: Exercise programs in accordance with individual needs can prevent muscle mass loss, decrease joint stiffness, and improve physical mobility. These programs are established to ensure that there is no formation of muscle tissues or development of joint contractures. 
• Occupational Therapy: It involves helping the patients to accept their situation and find ways on how to go about it when they developing some form of physical disability. This may include use of technological aids and strategies to increase independence. 

Intravenous Immunoglobulin (IVIG) Infusions: 

• IVIG Therapy: Off protocol which is usually prescribed for individuals who do not have positive feedback with conventional medicines. This involves administering directly into the veins of a patient pooled immunoglobulins that aids in the regulation of the immune response and combating inflammation. 
• Plasma Exchange (Plasmapheresis): That is, the patient’s plasma is removed and replaced with fresh plasma so that it does not contain autoantibodies that circulate in the patient’s blood and other inflammatory factors. It is indicated in severe or resistant cases especially in dermatomyositis. 

Muscle Biopsy: 

• Diagnostic Muscle Biopsy: Although not therapeutic, a muscle biopsy may be essential when diagnosing IIMs and deciding the patient’s management. This form of biopsy entails the use of a specialized instrument to take a small piece of muscle tissue for histopathological examination. 
• Radiologic Procedures: MRI or ultrasound may be employed for evaluation of muscle inflammatory changes, injury or participation in the process, planning of treatment and disease course follow up. 

Rheumatology

• Acute Phase: Initiate with corticosteroids and immunosuppressive agents. Conduct necessary investigations (e.g. muscle biopsy, blood investigation, etc). Manage acute distressing symptoms that may be present such as muscle weakness and muscle pain. IVIG or plasma exchange should be given at least in severe conditions which cannot be treated by corticosteroids or immunosuppressors. 
• Stabilization Phase: Optimize medications according to the patient’s response, as well as complications that may arise from the therapy. Begin the physical and occupational therapy to make the muscles stronger to perform the basic tasks. 
• Maintenance Phase: Ensure that the patients adhere to treatment plans and other medical prescriptions. It is particularly important to assess for disease activity and to identify other medications that patients may be taking and side effects they may be experiencing. Resume rehabilitation activities and address the outcomes and effects of physical disabilities. 
• Monitoring and Follow-Up Phase: Engage in periodic diagnosing to determine the state of these diseases, and the effectiveness of their treatment. If needed, change the treatment strategies.