POLYMYOSITIS,

DERMATOMYOSITIS,

AND INCLUSION BODY

MYOSITIS:Prepared & Presented by:

DR.KUCHA

POLYMYOSITIS, DERMATOMYOSITIS, AND INCLUSION BODY MYOSITIS:INTRODUCTION;

The inflammatory myopathies represent the largest group of acquired and potentially treatable causes of skeletal muscle weakness. They are classified into three major groups:

polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM).

POLYMYOSITISThe actual onset of PM is often not easily determined, and patients typically delay seeking medical advice for several weeks or even months. This is in contrast to DM, in which the rash facilitates early recognition. PM mimics many other myopathies and is a diagnosis of exclusion.

DERMATOMYOSITIS and INCLUSION BODY MYOSITIS

DERMATOMYOSITIS

DM is a distinctive entity identified by a characteristic rash accompanying, or more often preceding, muscle weakness.DM usually occurs alone but may overlap with scleroderma and mixed connective tissue disease.INCLUSION BODY MYOSITIS

In patients 50 years of age, IBM is the most common of the inflammatory myopathies. It is often misdiagnosed as PM and is suspected only later when a patient with presumed PM does not respond to therapy.

ASSOCIATION WITH MALIGNANCIES

The incidence of malignant conditions appears to be specifically increased only in patients with DM and not in those with PM or IBM.The most common tumors associated with DM are :

ovarian cancer, breast cancer, melanoma, colon cancer, and non-Hodgkin lymphoma.

OVERLAP SYNDROMESsclerotic thickening of the dermis, contractures, esophageal hypomotility, microangiopathy, and calcium deposits

ASSOCIATION WITH VIRAL INFECTIONS

Several viruses, including coxsackieviruses, influenza, paramyxoviruses, mumps, cytomegalovirus, and Epstein-Barr virus, have been indirectly associated with myositis.

Differential DiagnosisSUBACUTE OR CHRONIC PROGRESSIVE MUSCLE WEAKNESS : This may be due to denervating conditions such as the spinal muscular atrophies or amyotrophic lateral sclerosis ACUTE MUSCLE WEAKNESS : This may be caused by an acute neuropathy such as Guillain-Barr syndrome, transverse myelitis, a neurotoxin, or a neurotropic viral infection such as poliomyelitis or West Nile virus.

MYOFASCIITIS

NECROTIZING MYOSITIS

HYPERACUTE NECROTIZING FASCIITIS/MYOSITIS (FLESH-EATING DISEASE)

DRUG-INDUCED MYOPATHIES

Treatment: Therapy of Inflammatory Myopathies1. Glucocorticoids. Oral prednisone is the initial treatment of

choice;2. Other immunosuppressive drugs. Eg Azathioprine,

Methotrexate 3. Immunomodulation.o Calcinosis, a manifestation of DM, is difficult to treat;o IBM is generally resistant to immunosuppressive therapies.

Prednisone together with azathioprine or methotrexate is often tried

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