The hallmark of polymyositis is weakness and/or loss of muscle mass in the proximal musculature, as well as flexion of the neck and torso. These symptoms can be associated with marked pain in these areas as well. The hip extensors are often severely affected, leading to particular difficulty in ascending stairs and rising from a seated position. The skin involvement of dermatomyositis is absent in polymyositis. Dysphagia (difficulty swallowing) or other problems with esophageal motility occur in as many as 1/3 of patients. Low grade fever and peripheral adenopathy may be present. Foot drop in one or both feet can be a symptom of advanced polymyositis and inclusion body myositis. The systemic involvement of polymyositis includes interstitial lung disease (ILD) and cardiac disease, such as heart failure and conduction abnormalities.

Polymyositis tends to become evident in adulthood, presenting with bilateral proximal muscle weakness often noted in the upper legs due to early fatigue while walking. Sometimes the weakness presents itself as an inability to rise from a seated position without help or an inability to raise one's arms above one's head. The weakness is generally progressive, accompanied by lymphocytic inflammation (mainly cytotoxic T cells).

Polymyositis and the associated inflammatory myopathies have an associated increased risk of malignancy. The features they found associated with an increased risk of cancer was older age, age greater than 45, male sex, dysphagia, cutaneous necrosis, cutaneous vasculitis, rapid onset of myositis (<4 weeks), elevated creatine kinase, higher erythrocyte sedimentation rate and higher C-reactive protein levels. Several factors were associated with lower-than-average risk, including the presence of ILD, arthritis/arthralgia, Raynaud's syndrome, or anti-Jo-1 antibody. The malignancies that are associated are nasopharyngeal cancer, lung cancer, non-Hodgkin's lymphoma and bladder cancer, amongst others.

Cardiac involvement manifests itself typically as heart failure, and is present in up to 77% of patients.

Interstitial lung disease is found in up to 65% of patients with polymyositis, as defined by HRCT or restrictive ventilatory defects compatible with ILD.

The speed of the progression of JDMS is highly variable. Nearly all JDM patients have some skin involvement. The JDMS rash usually occurs as the initial symptom. Sometimes it is so slight as not to be recognized for what it is until muscle symptoms appear. Sometimes muscle symptoms never appear at all or occur very gradually over the course of months, and sometimes going from normal strength to being unable to walk within days. Usually, muscle symptoms appear weeks to months after the onset of the rash.

The main symptoms include several kinds of skin rash along with muscle weakness in both upper arms or thighs.

The vasculitis caused by JDMS manifests itself predominantly in two ways:

One is a distinctive rash. The rash often affects the face, eyelids, and hands, and sometimes the skin above joints, including the knuckles, knees, elbows, etc. The color of the rash is a pinkish purple, and is called heliotrope (after a flower of the same name with approximately this color). On the hands and face, the rash very closely resembles allergies, eczema, fifth disease, or other more common skin condition, but the heliotrope color is unique to the inflammatory process of JDMS. Some children develop calcinosis, which are calcium deposits under the skin. The rash is the source of the "dermato-" part of the name of the disease.

The second symptom caused by vasculitis is muscle inflammation. This symptom is the source of the "-myositis" part of the name of the disease ("myo" = muscle, "-itis" = inflammation of). Muscle Inflammation causes muscle weakness, which can cause fatigue, clumsiness, not keeping up physically with peers, and eventually inability to perform tasks like climbing stairs, lifting objects, and performing other manual tasks. Other signs may include falling, dysphonia, or dysphagia. The muscle weakness often causes a medical misdiagnosis of muscular dystrophy or other muscle disease. Some patients develop contractures, when the muscle shortens and causes joints to stay bent; exercise, occupational therapy, and physical therapy can prevent this. The muscles first affected tend to be proximal (i.e., neck, shoulders, back, and abdominal). About half of children with JDMS also have pain in their muscles.

Other symptoms may include irritability, weight loss, and mouth ulcers. When a child becomes irritable, fatigued, reluctant to socialize, and the face becomes flushed easily, physicians refer to this constellation of symptoms as "misery."

People with DM experience progressively worsening muscle weakness in the proximal muscles (for example, the shoulders and thighs). Tasks that use these muscles: standing from sitting, lifting, and climbing stairs, can prove challenging for people with DM.

How sIBM affects individuals is quite variable as is the age of onset (which generally varies from the forties upwards). Because sIBM affects different people in different ways and at different rates, there is no "textbook case."

Eventually, sIBM results in general, progressive muscle weakness. The muscles in the thighs called the quadriceps and the muscles in the arms that control finger flexion—making a fist—are usually affected early on. Common early symptoms include frequent tripping and falling, weakness going up stairs and trouble manipulating the fingers (including difficulty with tasks such as turning doorknobs or gripping keys). Foot drop in one or both feet has been a symptom of IBM and advanced stages of polymyositis (PM).

During the course of the illness, the patient's mobility is progressively restricted as it becomes hard for him or her to bend down, reach for things, walk quickly and so on. Many patients say they have balance problems and fall easily, as the muscles cannot compensate for an off-balanced posture. Because sIBM makes the leg muscles weak and unstable, patients are very vulnerable to serious injury from tripping or falling down. Although pain has not been traditionally part of the "textbook" description, many patients report severe muscle pain, especially in the thighs.

When present, difficulty swallowing (dysphagia) is a progressive condition in those with inclusion body myositis and often leads to death from aspiration pneumonia. Dysphagia is present in 40 to 85% of IBM cases.

IBM can also result in diminished capacity for aerobic exercise. This decline is most likely a consequence of the sedentary lifestyle that is often associated with the symptoms of IBM (i.e. progressive muscle weakness, decreased mobility, and increased level of fatigue). Therefore, one focus of treatment should be the improvement of aerobic capacity.

Patients with sIBM usually eventually need to resort to a cane or a walker and in most cases, a wheelchair eventually becomes a necessity.

"The progressive course of s-IBM leads slowly to severe disability. Finger functions can become very impaired, such as for manipulating pens, keys, buttons, and zippers, pulling handles, and firmly grasping handshakes. Arising from a chair becomes difficult. Walking becomes more precarious. Sudden falls, sometimes resulting in major injury to the skull or other bones, can occur, even from walking on minimally-irregular ground or from other minor imbalances outside or in the home, due to weakness of quadriceps and gluteus muscles depriving the patient of automatic posture maintenance. A foot-drop can increase the likelihood of tripping. Dysphagia can occur, usually caused by upper esophageal constriction that often can be symptomatically improved, for several months to years, by bougie dilation per a GI or ENT physician. Respiratory muscle weakness can sometimes eventuate."

There are a number of known causes of myopathy, and it is only once these have been ruled out that a clinician will assign an idiopathic inflammatory myopathy (IIM) syndrome to a case. The usual criteria for a diagnosis of PM are weakness in muscles of the head, neck, trunk, upper arms or upper legs; raised blood serum concentrations of some muscle enzymes such as creatine kinase; unhealthy muscle changes on electromyography; and biopsy findings of (i) muscle cell degeneration and regeneration and (ii) chronic inflammatory infiltrates in muscle cells. If heliotrope (purple) rash or Gottron's papules are also present, then the diagnosis is DM. In DM, myositis may not be clinically apparent but detectable via biopsy or MRI. If the criteria for PM are met but muscle weakness also affects the hands and feet or is not accompanied by pain IBM should be suspected, and confirmed when muscle cell biopsy reveals (i) cytoplasmic vacuoles fringed by basophilic granules and (ii) inflammatory infiltrate comprising mostly CD8 T lymphocytes and macrophages; and electron microscopy reveals filamentous inclusions in both cytoplasm and nucleus.

Inflammatory myopathy (inflammatory muscle disease or myositis) is disease featuring weakness and inflammation of muscles and (in some types) muscle pain. The cause of much inflammatory myopathy is unknown (idiopathic), and such cases are classified according to their symptoms and signs and electromyography, MRI and laboratory findings. It can also be associated with underlying cancer. The main classes of idiopathic inflammatory myopathy are polymyositis (PM), dermatomyositis (DM), and inclusion-body myositis (IBM).

Inclusion body myositis (IBM) is an inflammatory muscle disease characterized by slowly progressive weakness and wasting of both distal and proximal muscles, most apparent in the muscles of the arms and legs. There are two types: sporadic inclusion body myositis (sIBM), which is more common, and hereditary inclusion body myopathy (hIBM).

In sporadic inclusion body myositis [MY-oh-sigh-tis], two processes, one autoimmune and the other degenerative, appear to occur in the muscle cells in parallel. The inflammation aspect is characterized by the cloning of T cells that appear to be driven by specific antigens to invade muscle fibers. The degeneration aspect is characterized by the appearance of holes in the muscle cell vacuoles, deposits of abnormal proteins within the cells and in filamentous inclusions (hence the name inclusion body myositis).

Weakness comes on slowly (over months or years) and progresses steadily and usually leads to severe weakness and wasting of arm and leg muscles. It is more common in men than women. Patients may become unable to perform activities of daily living and most require assistive devices within 5 to 10 years of symptom onset. sIBM is not considered a disorder, but the risk of serious injury due to falls is increased. One common and potentially fatal complication is dysphagia. There is no effective treatment for the disease.

sIBM is a rare yet increasingly prevalent disease and is the most common cause of inflammatory myopathy in people over age 50. Recent research from Australia indicates that the incidence of IBM varies in different populations and ethnic groups. The authors found that the current prevalence was 14.9 per million in the overall population, with a prevalence of 51.3 per million population in people over 50 years of age. As seen in these numbers, sIBM is an age-related disease – its incidence increases with age and symptoms usually begin after 50 years of age. It is the most common acquired muscle disorder seen in people over 50, although about 20% of cases display symptoms before the age of 50.

Pain, which can vary in severity, is a common symptom in virtually all types of arthritis. Other symptoms include swelling, joint stiffness and aching around the joint(s). Arthritic disorders like lupus and rheumatoid arthritis can affect other organs in the body, leading to a variety of symptoms. Symptoms may include:

- Inability to use the hand or walk

- Stiffness, which may be worse in the morning, or after use

- Malaise and fatigue

- Weight loss

- Poor sleep

- Muscle aches and pains

- Tenderness

- Difficulty moving the joint

It is common in advanced arthritis for significant secondary changes to occur. For example, arthritic symptoms might make it difficult for a person to move around and/or exercise, which can lead to secondary effects, such as:

- Muscle weakness

- Loss of flexibility

- Decreased aerobic fitness

These changes, in addition to the primary symptoms, can have a huge impact on quality of life.

Arthritis is a term often used to mean any disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In some types other organs are also affected. Onset can be gradual or sudden.

There are over 100 types of arthritis. The most common forms are osteoarthritis (degenerative joint disease) and rheumatoid arthritis. Osteoarthritis usually occurs with age and affects the fingers, knees, and hips. Rheumatoid arthritis is an autoimmune disorder that often affects the hands and feet. Other types include gout, lupus, fibromyalgia, and septic arthritis. They are all types of rheumatic disease.

Treatment may include resting the joint and alternating between applying ice and heat. Weight loss and exercise may also be useful. Pain medications such as ibuprofen and paracetamol (acetaminophen) may be used. In some a joint replacement may be useful.

Osteoarthritis affects more than 3.8% of people while rheumatoid arthritis affects about 0.24% of people. Gout affects about 1 to 2% of the Western population at some point in their lives. In Australia about 15% of people are affected, while in the United States more than 20% have a type of arthritis. Overall the disease becomes more common with age. Arthritis is a common reason that people miss work and can result in a decreased quality of life. The term is from Greek "arthro-" meaning joint and "-itis" meaning inflammation.

Symptoms vary but they mostly involve skin disorders. The signs to look for include Raynaud's phenomenon, arthritis, myositis and scleroderma.

Visual symptoms include discoloring of the skin and painful swelling.

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

Affected individuals typically present with sudden painful proptosis, redness, and edema. Proptosis will vary according to the degree of inflammation, fibrosis, and mass effect. Occasionally, ptosis, chemosis, motility dysfunction (ophthalmoplegia), and optic neuropathy are seen. In the setting of extensive sclerosis there may be restriction, compression, and destruction of orbital tissue. Symptoms usually develop acutely (hours to days), but have also been seen to develop over several weeks or even months.Malaise, headaches, and nausea may accompany these symptoms. Other unusual presentations described include cystoid macular edema, temporal arteritis, and cluster headaches.

Pediatric IOI accounts for about 17% of cases idiopathic orbital inflammation. The most common sign is proptosis, but redness and pain are also experienced. Presentation varies slightly compared to adults with bilateral involvement, uveitis, disc edema and tissue eosinophilia being more common in this population. The presence of uveitis generally implies a poor outcome for pediatric IOI. Bilateral presentation may have a higher incidence of systemic disease.

Rheumatoid arthritis (RA), is a chronic inflammatory disorder that most typically begins in the small joints in your hands and feet. However, the course can begin with other nonspecific symptoms, such as tiredness. After attacking the smaller joints of the body, RA often progresses into larger joints, such as the shoulders, elbows, hips, and knees. Symptoms include joint pain, swelling, red and puffy hands, and fatigue. RA degrades the lining of the joints and causes swelling that is painful and can lead to joint deformity in the affected joints. Rheumatoid arthritis tends to worsen over time. Though there is no permanent cure, the course of the disease can be modified so that the damage is less, the patient is more comfortable and the patient can continue to engage in and enjoy daily activities. Treatment is most effective when it is begun as early as possible, before the process of deformity is far progressed, but some relief can be offered by treatment at any stage.

Signs and symptoms of drug-induced lupus erythematosus include the following:

- Joint pain (arthralgia) and muscle pain (myalgia)

- Fatigue

- Serositis —inflammation of the tissues lining the heart and lungs.

- Anti-histone antibodies in 95% of cases

These signs and symptoms are not side effects of the drugs taken which occur during short term use. DIL occurs over long-term and chronic use of the medications listed below. While these symptoms are similar to those of systemic lupus erythematosus, they are generally not as severe unless they are ignored which leads to more harsh symptoms, and in some reported cases, death.

Transient synovitis causes pain in the hip, thigh, groin or knee on the affected side. There may be a limp (or abnormal crawling in infants) with or without pain. In small infants, the presenting complaint can be unexplained crying (for example, when changing a diaper). The condition is nearly always limited to one side. The pain and limp can range from mild to severe.

Some children may have a slightly raised temperature; high fever and general malaise point to other, more serious conditions. On clinical examination, the child typically holds the hip slightly bent, turned outwards and away from the middle line (flexion, external rotation and abduction). Active and passive movements may be limited because of pain, especially abduction and internal rotation. The hip can be tender to palpation. The log roll test involves gently rotating the entire lower limb inwards and outwards with the patient on his back, to check when muscle guarding occurs. The unaffected hip and the knees, ankles, feet and spine are found to be normal.

Patients with acquired non-inflammatory myopathy typically experience weakness, cramping, stiffness, and tetany, most commonly in skeletal muscle surrounding the limbs and upper shoulder girdle.

The most commonly reported symptoms are:

- Muscle fatigue

- Pain

- Muscle spasms and cramps

- Tingling

- Numbness

- Tetany

- Loss of coordination and balance

- Lack of fine and gross motor control

- Muscular wasting and atrophy

As a syndrome, this condition is poorly defined. Diagnostic criteria require one or more antisynthetase antibodies (which target tRNA synthetase enzymes), and one or more of the following three clinical features: interstitial lung disease, inflammatory myopathy, and inflammatory polyarthritis affecting small joints symmetrically. Other supporting features may include fever, Raynaud's phenomenon and "mechanics hands"-thick, cracked skin usually on the palms and radial surfaces of the digits.

The disease, rare as it is, is more prevalent in women than in men. Early diagnosis is difficult, and milder cases may not be detected. Also, interstitial lung disease may be the only manifestation of the disease. Severe disease may develop over time, with intermittent relapses.

Idiopathic orbital inflammatory (IOI) disease, or orbital pseudotumor, refers to a marginated mass-like enhancing soft tissue involving any area of the orbit. It is the most common painful orbital mass in the adult population, and is associated with proptosis, cranial nerve (Tolosa–Hunt syndrome), uveitis, and retinal detachment. Idiopathic orbital inflammatory syndrome, also known as orbital pseudotumor, was first described by Gleason in 1903 and by Busse and Hochhmein. It was then characterized as a distinct entity in 1905 by Birch-Hirschfeld. It is a benign, nongranulomatous orbital inflammatory process characterized by extraocular orbital and adnexal inflammation with no known local or systemic cause. Its diagnosis is of exclusion once neoplasm, primary infection and systemic disorders have been ruled-out. Once diagnosed, it is characterized by its chronicity, anatomic location or histologic subtype.

Idiopathic orbital inflammation has a varied clinical presentation depending on the involved tissue. It can range from a diffuse inflammatory process to a more localized inflammation of muscle, lacrimal gland or orbital fat. Its former name, orbital pseudotumor, is derived due to resemblance to a neoplasm. However, histologically it is characterized by inflammation. Although a benign condition, it may present with an aggressive clinical course with severe vision loss and oculomotor dysfunction.

Masticatory muscle myositis (MMM) is an inflammatory disease in dogs affecting the muscles of mastication (chewing). It is also known as atrophic myositis or eosinophilic myositis. MMM is the most common inflammatory myopathy in dogs. The disease mainly affects large breed dogs. German Shepherd Dogs and Cavalier King Charles Spaniels may be predisposed. There is a similar disease of the eye muscles found in Golden Retrievers. Symptoms of acute MMM include swelling of the jaw muscles, drooling, and pain on opening the mouth. Ophthalmic signs may include third eyelid protrusion, red eyes, and exophthalmos (protruding eyeballs). In chronic MMM there is atrophy of the jaw muscles, and scarring of the masticatory muscles due to fibrosis may result in inability to open the mouth (trismus). The affected muscles include the temporalis, masseter, and pterygoid muscles. The disease is usually bilateral.

MMM is caused by the presence of 2M fibers in the muscles of the jaw. 2M fibers are not found elsewhere in the body. The immune system recognizes these proteins as foreign to the body and attacks them, resulting in inflammation. Diagnosis of MMM is through either biopsy of the temporalis or masseter muscles or the 2M antibody assay, in which blood serum of the possible MMM-dog is reacted with temporalis tissue of a normal dog, or both. False negatives by the 2M antibody assay may be obtained if MMM is end-stage with destruction of type 2M fibers and marked fibrosis. Treatment is usually with corticosteroids such as prednisone, often with decreasing doses for up to 4–6 months, and in the case of trismus, manual opening of the mouth under anesthesia. Feeding very soft or liquid food during this time is usually necessary. The ultimate degree of recovery of jaw function and muscle mass will depend upon the extent of damage to the muscle tissue. Recurrence of MMM may occur. Misdiagnosis of MMM as a retroorbital abscess based on physical examination and finding of trismus leads to inappropriate treatment with antibiotics, which will not impede the progress of MMM.

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

Pain in or around the hip and/or limp in children can be due to a large number of conditions. Septic arthritis (a bacterial infection of the joint) is the most important differential diagnosis, because it can quickly cause irreversible damage to the hip joint. Fever, raised inflammatory markers on blood tests and severe symptoms (inability to bear weight, pronounced muscle guarding) all point to septic arthritis, but a high index of suspicion remains necessary even if these are not present. Osteomyelitis (infection of the bone tissue) can also cause pain and limp.

Bone fractures, such as a toddler's fracture (spiral fracture of the shin bone), can also cause pain and limp, but are uncommon around the hip joint. Soft tissue injuries can be evident when bruises are present. Muscle or ligament injuries can be contracted during heavy physical activity —however, it is important not to miss a slipped upper femoral epiphysis. Avascular necrosis of the femoral head (Legg-Calvé-Perthes disease) typically occurs in children aged 4–8, and is also more common in boys. There may be an effusion on ultrasound, similar to transient synovitis.

Neurological conditions can also present with a limp. If developmental dysplasia of the hip is missed early in life, it can come to attention later in this way. Pain in the groin can also be caused by diseases of the organs in the abdomen (such as a psoas abscess) or by testicular disease. Rarely, there is an underlying rheumatic condition (juvenile idiopathic arthritis, Lyme arthritis, gonococcal arthritis, ...) or bone tumour.

Osteoarthritis is a joint disease that causes the cushion layer between one's bones, or cartilage to wear away. It is also called degenerative joint disease. Symptoms are similar to RA and develop in the same slow manner. They include pain, tenderness in the knee, stiffness when standing or walking, loss of flexibility, and grating sensations that can be heard when the knee joint is used.

Osteoarthritis in the knee begins with the gradual deterioration of cartilage. Without the protective cartilage, the bones begin to rub together, causing pain, loss of mobility, and deformity. It affects approximately 16 million people. The majority of arthritis cases involving the knee are osteoarthritic cases.