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Dermatomyositis

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Inflammatory myopathy and skin manifestations.

An autoimmune disease characterized by an erythematous rash and symmetrical proximal muscle weakness.

Skin manifestations of the face and metacarprophalangeal joints are characteristic.

Skin papules that form are often painful and ulcerated, and they are usually located on the palmar surface of the metacarpophalangeal and inter-phalangeal joint.

Skin findings suggestive of dermatomyositis include periorbital erythema and Edema, erythema on the upper chest consistent with a V-sign, and erythema involving the upper back, the shawl sign.

Characteristic skin findings include scalp erythema, mid facial erythema involving the nasal labial folds.

Additional findings include non-scarring alopecia, scalp erythema, and pruritus.

Gottron’s Papules are pink to iolations lichen oof papules on the metacarpalphalangeal for inter-phalangeal joints and or pathognomonic for dermatomyositis.

Bohan and Peter’s criteria-an inflammatory myositis with dermatologic features including Gottron’s papules, heliotrope rash over the eyelids, scaly erythematous rash over the dorsum of the hands or involvement of the knees, elbows, and medial malleoli, face, neck, and upper torso.

Proximal nailfold can be erythematous and edematous, and cuticles can be ragged and hypertrophied.

On Dermoscopy dilated capillary loops, capillary-loop drop out, and microhemorrhages can be seen.

Muscle biopsies revealed a mononuclear, inflammatory cell exudate in a perivascular and perifascicular distribution with degenerating and regenerating muscle fibers and perifascicular atrophy.

Muscle inflammation leads to rapid and long-standing muscle necrosis, reflected by a rise and circulating muscle enzymes such is creatine phosphokinase.

Patients classically have symmetric, proximal muscle weakness, which limits their ability to stand from a seated position, to climb stairs, or reach overhead.

The accumulation of immune cells in muscle, supported by circulating auto antibodies directed against nuclear components and constituents of muscle cells has led to the classification of this process as an autoimmune disease.

Anti-MDA, is an elevated is in autoantibody seen in the severe form of the disease compounded by lung involvement.

MDA-5 is a receptor of the innate immune system.

MDA-5 identifies viral dsRNA within the cytosol, and prompts the manufacture of type one interferons, which ultimately provokes a apoptosis of infected cells.

The precise roles MDA-5 and the anti-MDA-5 autoantibodies play in dermatomyositis are not completely understood.

Production of anti-MDA-5 auto antibodies occurs during viral infections of the skin and lung epithelium and their formation is triggered by the release of fragments of MDA-5 after its proteolysis within infected cells.

Approximately 50-100% of patients positive for Anti-MDA-5 have a diagnosis clinically of amyopathic dermatomyositis.

Amyopathic dermatomyositis is a subtype of dermatomyositis in which the characteristic skin findings are present in the absence of muscle involvement.

Amyopathic dermatomyositis is a diagnosis made after six months of the absence of muscle involvement and is confirmed diagnosis if muscle involvement remains absent two years after the onset of skin symptoms.

Amyopathic dermatomyositis represents approximately 20% of dermatomyositis cases.

Anti-MDA-5 is more commonly found in the Asian population.

The exact risk in incidence in association with cancer is unclear.

All patients should be screened for cancer.

Cancer is reported in 15–27% of patients and may precede, occur concurrently with, or follow the diagnosis.

Highest risk of cancer occurs in the first year after symptom onset but remains elevated through 3-5 years.

Cancer diagnoses associated with dermatomyositis include: lung, breast, ovarian, pancreatic, and colorectal cancers, among others.

Creatine kinase and aldolase levels should be measured in all patients with skin findings consistent with dermatomyositis, including those without muscle involvement.

It occurs in women twice as often as men and has bimodal peaks in childhood and the 4th-6 decades of life.

Patient with myositis specific autoantibodies TIF-1gamma have a higher risk of cancer.

Malignant disease may occur before the onset, concurrently or as a later paraneoplastic syndrome manifestation.

Adult patients with tomato myositis should be screened for associated interstitial lung disease and cancer.

It may follow a course that independent of the treated malignant disease.

There is an increased incidence of cancer in the first 3-5 years following the diagnosis of myositis.

Prevalence of this entity with cancer is associated in patients over the age of 50 and suggests a poor prognosis (Yazici Y).

Associated with cancers of the ovaries, lung, stomach, and colorectum.

Most often the diagnosis is a harbinger of a malignancy.

The relationship between myositis and cancer is hypothesized to be one of a compromised immune function.

In patients with cancer disappearance of skin and muscular signs after treatment of the malignant lesion indicates low probable paraneoplastic nature of the process.

All patients with the diagnosis should be evaluated for the presence of a malignancy.

Modern treatment has reduced mortality to less than 10%.

Risk of malignancy 6.5 fold increase.

Most common malignancies associated are ovarian, gastric and lymphoma.

Poor prognostic indicators include recalcitrant disease, delay in diagnosis, older age, malignancy, fever, asthenia, anorexia, pulmonary interstitial fibrosis, dysphagia and leucocytosis.

Interstitial lung disease is present in up to 40% of patients with dermatomyositis, and the risk is higher among patients with auto antibodies to RNA synthetase enzymes and melanoma differentiation-associated protein five ( MDA5) among whom as many as 80% will have interstitial lung disease.

Malignancy, cardiac and pulmonary dysfunction are the most common causes of death.

Agents used to control inflammation were initially steroids, often at high dose.

Steroids are active but have many side effects including steroid induced myopathy and other agents have been added including: azathioprine, methotrexate , and cyclosporine.

Anti-MDA ia an autoantibody in Dermatomyositis that is a marker of the severe form of the disease compounded by lung involvement.

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