Treatment
During pregnancy
Antenatal management only occurs if a mother has had a previously affected baby or a family member has had an affected baby.Interventions can be classified as invasive or non-invasive.A review of the evidence has shown that invasive management resulted in a relatively high complication rate (mainly preterm emergency cesarean section) of 11% per treated pregnancy. Noninvasive management was also shown to be effective, but without the relatively high rate of adverse outcomes seen with invasive management. They concluded that first-line antenatal management in NAIT should be non-invasive with weekly intravenous immunoglobulin administration, with or without the addition of corticosteroids.Recent international guidelines have now recommended non-invasive management of NAIT. Previously there had been no international consensus on the optimal antenatal management of NAIT, and numerous strategies had been used in different centers that specialized in antenatal treatment. Invasive management
Fetal blood sampling from the umbilical cord and intrauterine platelet transfusion was the first antenatal treatment for NAIT to prevent intracerebral hemorrhage. However, this is no longer recommended routinely because of the serious risk of harms. Cordocentesis in the presence of a low platelet count may lead to serious complications, these included slowing of the babys heart (fetal bradycardia), tamponade of the cord, and bleeding complications in the baby, including exsanguination. Fetal blood sampling is estimated to cause death of the baby in 1.3% of procedures, however the incidence varies significantly from center to center.
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 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, and Gottron papulesThe 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.Dermatomyositis is associated with autoantibodies, especially antinuclear antibodies (ANA).