00:00 / 00:00
Lordosis, kyphosis, and scoliosis
Osteomalacia and rickets
Paget disease of bone
Calcium pyrophosphate deposition disease (pseudogout)
Juvenile idiopathic arthritis
Inclusion body myopathy
Degenerative disc disease
Spinal disc herniation
Achilles tendon rupture
Anterior cruciate ligament injury
Iliotibial band syndrome
Patellar tendon rupture
Patellofemoral pain syndrome
Carpal tunnel syndrome
Thoracic outlet syndrome
Radial head subluxation (Nursemaid elbow)
Rotator cuff tear
Lambert-Eaton myasthenic syndrome
Limited systemic sclerosis (CREST syndrome)
Mixed connective tissue disease
Systemic lupus erythematosus
Developmental dysplasia of the hip
Osgood-Schlatter disease (traction apophysitis)
Slipped capital femoral epiphysis
Back pain: Pathology review
Bone disorders: Pathology review
Bone tumors: Pathology review
Gout and pseudogout: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
Myalgias and myositis: Pathology review
Neuromuscular junction disorders: Pathology review
Pediatric musculoskeletal disorders: Pathology review
Rheumatoid arthritis and osteoarthritis: Pathology review
Scleroderma: Pathology review
Seronegative and septic arthritis: Pathology review
Sjogren syndrome: Pathology review
Systemic lupus erythematosus (SLE): Pathology review
Polymyositis / Dermatomyositis Diagnosis and Treatment
Polymyositis / Dermatomyositis Disease
Polymyositis & Dermatomyositis
In polymyositis, “myos-“ refers to the muscles, “poly-“ means many, and “-itis” refers to inflammation, so polymyositis is an inflammatory disorder which involves many muscle groups around the body.
Polymyositis is an immune- mediated disease, meaning that the immune system attacks the muscles in our own body.
Normally, the cells of the immune system are ready to spot and destroy anything foreign that could cause the body harm.
To help with this, most cells in the body have a set of proteins that combine together to form something called a major histocompatibility complex, or MHC, class I molecule that sits on the surface of their cell membrane.
These surface proteins act kind of like a serving platter, presenting molecules from within the cell for the immune system to continually sample.
Normally though the molecule’s just a sample from the cell, and the immune system recognizes it as harmless, and this is known as a self-antigen, and there’s no response.
But when a cell is actually invaded by a pathogen like a virus, viral antigens are presented on the MHC class I molecule, and that sparks a different immune response.
A type of T-lymphocyte, called a CD8+ T-cell, also known as a cytotoxic T-cell, uses its T-cell receptors to bind to the antigen presented by the MHC class I molecule.
If the cytotoxic T-cell binds strongly, than the antigen is recognized as foreign, and the cytotoxic T-cell secretes a whole lot of perforin and granzymes.
Perforin forms big holes in the infected cell and that allows the granzymes to enter the cell.
Once inside, the granzymes induce apoptosis, or programmed cell death.
As if that weren’t enough, the cytotoxic T-cells have a protein called Fas ligand on their surface, and it binds to a molecule called Fas on the surface of the infected cell.
Polymyositis is an inflammatory disorder of the muscles, caused mainly by cytotoxic T- cells destroying muscle tissue due to molecular mimicry and resulting in bilateral proximal muscle weakness of large muscle groups. It is characterized by muscle weakness, muscle pain, and difficulty with activities of daily living. Its diagnosis involves elevated serum creatinine kinase and myositis- specific antibodies, and it is treated with corticosteroids and specialized physical exercise.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.