(ADM), formerly known as "dermatomyositis sine myositis". Muscles 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 become increasingly difficult for people with dermatomyositis. Other Around 30% of people have swollen, painful joints, but this is generally mild. In some people, the condition affects the lungs, and they may have a cough or difficulty breathing. If the disease 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. There are further complications possible with Dermatomyositis. These complications include difficulty swallowing due to the muscles in the esophagus being affected which can result in malnutrition and can cause the breathing of food or liquids, into the lungs. Causes The cause is unknown, but it may result from an initial viral infection or cancer, either of which could raise an autoimmune response. Between 7 and 30% of dermatomyositis cases arise from cancer, probably as an autoimmune response. The most commonly associated cancers are ovarian cancer, breast cancer, and lung cancer. Between 18 and 25 per cent of people with amyopathic DM also have cancer. 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. Diagnosis The diagnosis of dermatomyositis is based on five criteria, which are also used to differentially diagnose with respect to polymyositis: Muscle weakness in both thighs or both upper arms 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 Using electromyography (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 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) Rashes typical of dermatomyositis, which include heliotrope rash, Gottron sign,