Childhood dermatomyositis
Encyclopedia
Childhood dermatomyositis is a connective-tissue disease related to polymyositis
, characterized by inflammation
of the muscles and the skin. It differs from adult dermatomyositis
in several ways, and has two common variants. The more common form is the "Brunsting type," in which slow, progressive muscle weakness with calcinosis
can be easily treated with corticosteroid
s. The second type is known as "Banker type," characterized by a vasculitis
of the muscles and gastrointestinal tract, rapid onset of severe weakness, steroid unresponsiveness, and high death date.
with a characteristic "spike and wave" pattern, and abnormal CPK
or aldolase
levels. Conclusive diagnosis requires a muscle biopsy that shows perifascicular infiltration of inflammatory cells.
s and typically disappears within six months of treatment. Muscular calcifications can be surgically removed, but doing so may result in poor wound healing; calcifications can be reduced with bisphosphonate
s.
Children with the rare polycyclic form of dermatomyositis can also be treated with corticosteroids and methotrexate
, but respond poorly. Muscle cells that die during the inflammatory phase of dermatomyositis are non-renewable, which can lead to permanent weakness.
Polymyositis
Polymyositis is a type of chronic inflammation of the muscles related to dermatomyositis and inclusion body myositis.-Signs and symptoms:...
, characterized by inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the muscles and the skin. It differs from adult dermatomyositis
Dermatomyositis
Dermatomyositis is a connective-tissue disease related to polymyositis and Bramaticosis that is characterized by inflammation of the muscles and the skin.- Causes :...
in several ways, and has two common variants. The more common form is the "Brunsting type," in which slow, progressive muscle weakness with calcinosis
Calcinosis
-Dystrophic calcification:The most common type of calcinosis is dystrophic calcification. This type of calcification can occur as a response to any soft tissue damage, including that involved in implantation of medical devices.-Metastatic calcification:...
can be easily treated with corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s. The second type is known as "Banker type," characterized by a vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
of the muscles and gastrointestinal tract, rapid onset of severe weakness, steroid unresponsiveness, and high death date.
Pathology
Dermatomyositis is confirmed by proximal muscle weakness, an electromyographyElectromyography
Electromyography is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph, to produce a record called an electromyogram. An electromyograph detects the electrical potential generated by muscle...
with a characteristic "spike and wave" pattern, and abnormal CPK
Creatine kinase
Creatine kinase , also known as creatine phosphokinase or phospho-creatine kinase , is an enzyme expressed by various tissues and cell types. CK catalyses the conversion of creatine and consumes adenosine triphosphate to create phosphocreatine and adenosine diphosphate...
or aldolase
Aldolase
Aldolase A is an enzyme that catalyses a reverse aldol reaction: The substrate, fructose 1,6-bisphosphate is broken down into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate . This reaction is a part of glycolysis. Three aldolase isozymes , encoded by three different genes, are...
levels. Conclusive diagnosis requires a muscle biopsy that shows perifascicular infiltration of inflammatory cells.
Treatment
The more common type of dermatomyositis, the unicyclic "Brunsting type", responds well to corticosteroidCorticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s and typically disappears within six months of treatment. Muscular calcifications can be surgically removed, but doing so may result in poor wound healing; calcifications can be reduced with bisphosphonate
Bisphosphonate
Bisphosphonates are a class of drugs that prevent the loss of bone mass, used to treat osteoporosis and similar diseases...
s.
Children with the rare polycyclic form of dermatomyositis can also be treated with corticosteroids and methotrexate
Methotrexate
Methotrexate , abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate...
, but respond poorly. Muscle cells that die during the inflammatory phase of dermatomyositis are non-renewable, which can lead to permanent weakness.