Some of these additional tests may include a WBC differential, a blood smear review, or in severe conditions, a bone marrow examination. A differential may indicate which type of WBC is low or high while a blood smear and/or bone marrow biopsy can reveal the presence of abnormal and/or immature WBCs. ^ Back to top.
The most common types are dermatomyositis, polymyositis, necrotising autoimmune myopathy and sporadic inclusion body myositis (IBM). Although dermatomyositis affects the skin and muscles, it may also affect other parts of the body such as joints, oesophagus, lungs and heart.
The most common are: 1  Polymyositis (PM) affects the muscles nearest the trunk. 2  Dermatomyositis (DM) causes both muscle inflammation and skin rash. 3  Inclusion body myositis (IBM) appears to overlap with degenerative muscle disease and mostly affects people over 50. 4  Juvenile myositis begins in childhood or adolescence. Some IIMs overlap with other health conditions like arthritis or cancer. Most cases of IIM are chronic, meaning symptoms come and go over a long period of time. Symptoms during flares (periods of active disease) may range from mild to severe and disabling.