Dermatomyositis

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Dermatomyositis
Dermatomyositis.jpg
Discrete red areas overlying the knuckles in a person with juvenile dermatomyositis. These are known as Gottron's papules.
Specialty Rheumatology
SymptomsRash, muscle weakness, weight loss, fever [1]
Complications Calcinosis, lung inflammation, heart disease [1] [2]
Usual onset40s to 50s [3]
Duration Long term [1]
CausesUnknown [1]
Diagnostic method Based on symptoms, blood tests, electromyography, muscle biopsies [3]
Differential diagnosis Polymyositis, inclusion body myositis, scleroderma [3]
TreatmentMedication, physical therapy, exercise, heat therapy, orthotics, assistive devices, rest [1]
Medication Corticosteroids, methotrexate, azathioprine [1]
Frequency~ 1 per 100,000 people per year [3]

Dermatomyositis (DM) is a long-term inflammatory disorder which affects skin and the muscles. [1] Its symptoms are generally a skin rash and worsening muscle weakness over time. [1] These may occur suddenly or develop over months. [1] Other symptoms may include weight loss, fever, lung inflammation, or light sensitivity. [1] Complications may include calcium deposits in muscles or skin. [1]

Contents

The cause is unknown. [1] Theories include that it is an autoimmune disease or a result of a viral infection. [1] It is a type of inflammatory myopathy. [1] Diagnosis is typically based on some combination of symptoms, blood tests, electromyography, and muscle biopsies. [3]

While no cure for the condition is known, treatments generally improve symptoms. [1] Treatments may include medication, physical therapy, exercise, heat therapy, orthotics and assistive devices, and rest. [1] Medications in the corticosteroids family are typically used with other agents such as methotrexate or azathioprine recommended if steroids are not working well. [1] Intravenous immunoglobulin may also improve outcomes. [1] Most people improve with treatment and in some the condition resolves completely. [1]

About one per 100,000 people per year are newly affected. [3] The condition usually occurs in those in their 40s and 50s with women being affected more often than men. [3] People of any age, however, may be affected. [3] The condition was first described in the 1800s. [4]

Signs and symptoms

The main symptoms include several kinds of skin rash along with muscle weakness in both upper arms or thighs. [2]

Skin

One form the rashes take is called "heliotrope" (a purplish color) or lilac, but may also be red. It can occur around the eyes along with swelling, but also occurs on the upper chest or back what is called the "shawl" (around the neck) or "V-sign" above the breasts and may also occur on the face, upper arms, thighs, or hands. [5] Another form the rash takes is called Gottron's sign which are red or violet, sometimes scaly, slightly raised papules that erupt on any of the finger joints (the metacarpophalangeal joints or the interphalangeal joints). [5] [6] Gottron's papules may also be found over other bony prominences including the elbows, knees, or feet. All these rashes are made worse by exposure to sunlight, and are often very itchy, painful, and may bleed. [6]

If a person exhibits only skin findings characteristic of DM, without weakness or abnormal muscle enzymes, then he or she may be experiencing amyopathic dermatomyositis (ADM), formerly known as "dermatomyositis sine myositis". [7]

Muscles

People with DM experience progressively worsening muscle weakness in the proximal muscles (for example, the shoulders and thighs). [8] Tasks that use these muscles: standing from sitting, lifting, and climbing stairs, can become increasingly difficult for people with dermatomyositis. [8]

Other

Around 30% of people have swollen, painful joints, but this is generally mild. [9]

In some people, the condition affects the lungs, and they may have a cough or difficulty breathing. If the condition affects the heart, arrhythmias may occur. If it affects the blood vessels in the stomach or intestines, which is more common in juvenile DM, the people might vomit blood, have black tarry bowel movements, or may develop a hole somewhere in their GI tract. [9]

Causes

The cause is unknown, but it may result from an initial viral infection or cancer, either of which could raise an autoimmune response. [9]

Between 7 and 30% of dermatomyositis arise from cancer, probably as an autoimmune response. [10] The most commonly associated cancers are ovarian cancer, breast cancer, and lung cancer. [10] 18 to 25% of people with amyopathic DM also have cancer. [6] Malignancy in association with dermatomyositis is more prevalent after age 60.

Some cases are inherited, and HLA subtypes HLA-DR3, HLA-DR52, and HLA-DR6 seem to create a disposition to autoimmune dermatomyositis. [9]

Diagnosis

Calcification from dermatomyositis Dermatomyocitis.png
Calcification from dermatomyositis
X-Ray of the knee in a person with dermatomyositis. XRaydermatomyositis.jpg
X-Ray of the knee in a person with dermatomyositis.
Micrograph of dermatomyositis, muscle biopsy, H&E stain Dermatomyositis - high mag.jpg
Micrograph of dermatomyositis, muscle biopsy, H&E stain

The diagnosis of dermatomyositis is based on five criteria, which are also used to differentially diagnose with respect to polymyositis: [7]

  1. Muscle weakness in both thighs or both upper arms
  2. Using a blood test, finding higher levels of enzymes found in skeletal muscle, including creatinine kinase, aldolase, and glutamate oxaloacetate, pyruvate transaminases and lactate dehydrogenase
  3. Using testing of electric signalling in muscles, finding all three of: erratic, repetitive, high-frequency signals; short, low-energy signals between skeletal muscles and motor neurons that have multiple phases; and sharp activity when a needle is inserted into the muscle
  4. Examining a muscle biopsy under a microscope and finding mononuclear white blood cells between the muscle cells, and finding abnormal muscle cell degeneration and regeneration, dying muscle cells, and muscle cells being consumed by other cells (phagocytosis)
  5. Rashes typical of dermatomyositis, which include heliotrope rash, Gottron sign, and Gottron papules

The fifth criterion is what differentiates dermatomyositis from polymyositis; the diagnosis is considered definite for dermatomyositis if three of items 1 through 4 are present in addition to 5, probable with any two in addition to 5, and possible if just one is present in addition to 5. [7]

Dermatomyositis is associated with autoantibodies, especially antinuclear antibodies (ANA). [9] Around 80% of people with DM test positive for ANA and around 30% of people have myositis-specific autoantibodies which include antibodies to aminoacyl-tRNA synthetases (anti-synthetase antibodies), including antibodies against histidine—tRNA ligase (also called Jo-1); antibodies to signal recognition particle (SRP); and anti-Mi-2 antibodies. [9]

Magnetic resonance imaging may be useful to guide muscle biopsy and to investigate involvement of internal organs; [11] X-ray may be used to investigate joint involvement and calcifications. [12]

A given case of dermatomyositis may be classified as amyopathic dermatomyositis if only skin is affected and no muscle weakness for longer than 6 months is seen according to one 2016 review, [7] or two years according to another. [6]

Classification

Dermatomyositis is a form of systemic connective tissue disorder, a class of diseases that often involve autoimmune dysfunction. [9] [13]

It has also been classified as an idiopathic inflammatory myopathy along with polymyositis, necrotizing autoimmune myositis, cancer-associated myositis, and sporadic inclusion body myositis. [14]

A form of this disorder that strikes children is known as juvenile dermatomyositis. [15]

Treatment

No cure for dermatomyositis is known, 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.[ citation needed ]

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. [16]

Antimalarial medications, especially hydroxychloroquine and chloroquine, are used to treat the rashes, as they are in similar conditions. [6]

Rituximab is used when people do not respond to other treatments. [17] [18]

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, methotrexate, azathioprine, and mycophenolate mofetil. None appears to be very effective, but among them, intravenous immunoglobulin has had the best outcomes. [7]

Prognosis

Before the advent of modern treatments such as prednisone, intravenous immunoglobulin, plasmapheresis, chemotherapies, and other drugs, the prognosis was poor. [19]

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.[ medical citation needed ]

The risk of death from the condition is much higher if the heart or lungs are affected. [14] [16]

Epidemiology

Incidence of DM peaks at ages 40–50, but the disease can affect people of all ages. [20] [3] It tends to affect more women than men. [3] The prevalence of DM ranges from one to 22 per 100,000 people. [21] [22] [23]

History

The diagnostic criteria were proposed in 1975 and became widely adopted. [6] [24] Amyopathic DM, also called DM sine myositis, was named in 2002. [6]

Society and culture

Research

As of 2016, research was ongoing into causes for DM, as well as biomarkers; [30] clinical trials were ongoing for use of the following drugs in DM: ajulemic acid (Phase II), adrenocorticotropic hormone gel (Phase IV, open label), IMO-8400, an antagonist of Toll-like receptor 7,8 and 9 (Ph II), abatacept (Phase IV, open label), and sodium thiosulfate (Phase II). [6]

Related Research Articles

Inclusion body myositis (IBM) is the most common inflammatory muscle disease in older adults. The disease is characterized by slowly progressive weakness and wasting of both proximal muscles and distal muscles, most apparent in the finger flexors and knee extensors. IBM is often confused with an entirely different class of diseases, called hereditary inclusion body myopathies (hIBM). The "M" in hIBM is an abbreviation for "myopathy" while the "M" in IBM is an abbreviation for "myositis". These diseases should not be confused with each other. In IBM, two processes appear to occur in the muscles in parallel, one autoimmune and the other degenerative. Inflammation is evident from the invasion of muscle fibers by immune cells. Degeneration is characterized by the appearance of holes, deposits of abnormal proteins, and filamentous inclusions in the muscle fibers. sIBM is a rare disease, with a prevalence ranging from 1 to 71 individuals per million.

Lambert–Eaton myasthenic syndrome

Lambert–Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder characterized by muscle weakness of the limbs.

Myalgia is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, especially when there has been no trauma. Long-lasting myalgia can be caused by metabolic myopathy, some nutritional deficiencies, and chronic fatigue syndrome.

Juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is an idiopathic inflammatory myopathy (IMM) of presumed autoimmune dysfunction resulting in muscle weakness among other complications. It manifests itself in children; it is the pediatric counterpart of dermatomyositis. In JDM, the body's immune system attacks blood vessels throughout the body, causing inflammation called vasculitis. In the United States, the incidence rate of JDMS is approximately 2-3 cases per million children per year. The UK incidence is believed to be between 2-3 per million children per year, with some difference between ethnic groups. The sex ratio is approximately 2:1. Other Idiopathic inflammatory myopathies include; juvenile polymyositis (PM), which is rare and not as common in children as in adults.

Myopathy Muscular disease in which the muscle fibers do not function correctly

In medicine, myopathy is a disease of the muscle in which the muscle fibers do not function properly. This results in muscular weakness. Myopathy means muscle disease. This meaning implies that the primary defect is within the muscle, as opposed to the nerves or elsewhere. Muscle cramps, stiffness, and spasm can also be associated with myopathy.

Cryoglobulinemia Medical condition

Cryoglobulinemia is a medical condition in which the blood contains large amounts of pathological cold sensitive antibodies called cryoglobulins – proteins that become insoluble at reduced temperatures. This should be contrasted with cold agglutinins, which cause agglutination of red blood cells.

Polymyositis

Polymyositis (PM) is a type of chronic inflammation of the muscles related to dermatomyositis and inclusion body myositis. Its name means "inflammation of many muscles". The inflammation of polymyositis is mainly found in the endomysial layer of skeletal muscle, where as dermatomyositis is characterized primarily by inflammation of the perimysial layer of skeletal muscles.

An autoantibody is an antibody produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases are caused by such autoantibodies.

Myositis is inflammation or swelling of the muscles. Injury, medicines, infection, or an immune disorder can lead to myositis.

Masticatory muscle myositis

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. 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.

Neuromuscular disease

Neuromuscular disease is a broad term that encompasses many diseases and ailments that impair the functioning of the muscles, either directly, being pathologies of the voluntary muscle, or indirectly, being pathologies of nerves or neuromuscular junctions.

Mixed connective tissue disease

Mixed connective tissue disease commonly abbreviated as MCTD, is an autoimmune disease characterized by the presence of elevated blood levels of a specific autoantibody, now called anti-U1 ribonucleoprotein (RNP) together with a mix of symptoms of systemic lupus erythematosus (SLE), scleroderma, and polymyositis. The idea behind the "mixed" disease is that this specific autoantibody is also present in other autoimmune diseases such as systemic lupus erythematosus, polymyositis, scleroderma, etc. MCTD was characterized as an individual disease in 1972 by Sharp et al., and the term was introduced by Leroy in 1980.

Scleromyositis, is an autoimmune disease. People 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.

Autoimmune disease Abnormal immune response to a normal body part

An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. There are at least 80 types of autoimmune diseases. Nearly any body part can be involved. Common symptoms include low grade fever and feeling tired. Often symptoms come and go.

Inflammatory myopathy

Inflammatory myopathy is disease featuring weakness and inflammation of muscles and 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).

Dermatopolymyositis is a family of myositis disorders that includes polymyositis and dermatomyositis. As such, it includes both a distinctive skin rash and progressive muscular weakness. It is a rare disease.

Although they vary in particulars, polymyositis, dermatomyositis and inclusion body myositis are idiopathic inflammatory myopathies (IIM) primarily characterized by chronic inflammation of human skeletal muscle tissue that ultimately causes the necrosis of muscle cells. This degeneration leads to muscle tissue wasting, weakness and fatigue among other serious effects. Until recently, exercise has been avoided as a type of therapy, and even forbidden due to the risk of triggering or amplifying inflammation. However, several studies have been conducted to test this assumption and have shown that aerobic exercise as well as resistance training can maintain and even improve quality of life for IIM-affected individuals without increased inflammatory response.

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

Immunoglobulin therapy, also known as normal human immunoglobulin (NHIG), is the use of a mixture of antibodies (immunoglobulins) to treat a number of health conditions. These conditions include primary immunodeficiency, immune thrombocytopenic purpura, chronic inflammatory demyelinating polyneuropathy, Kawasaki disease, certain cases of HIV/AIDS and measles, Guillain-Barré syndrome, and certain other infections when a more specific immunoglobulin is not available. Depending on the formulation it can be given by injection into muscle, a vein, or under the skin. The effects last a few weeks.

Statin-associated autoimmune myopathy (SAAM), also known as anti-HMGCR myopathy, is a very rare form of muscle damage caused by the immune system in people who take statin medications. However, there are cases of SAAM in patients who have not taken statin medication, and this can be explained by the exposure to natural sources of statin such as red yeast rice, which is statin rich. This theory is supported by the higher prevalence of statin-naive SAAM patients in Asian cohorts, who have statin-rich diets.

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PD-icon.svg This article incorporates  public domain material from the United States Department of Health and Human Services document: "NINDS Dermatomyositis Information Page" . Retrieved 12 December 2016.

Classification
D
External resources