• bilateral

• affects large and proximal muscles (example: shoulders, hips)

• spares distal muscles (example: hands)

• progresses over weeks to months

Patient can present difficulty in several daily activities... (Myositis Support and Understanding, 2019b)

• climbing stairs

• rising from chair

• lifting arms

Mild myalgia

Dysphagia, if pharynx or esophagus is affected

• dyspnea

• dysphonia

Fatigue

Kumar, V., Abbas, A. K., & Aster, J. C. (2020). Robbins and Cotran pathologic basis of disease (10th ed.). Elsevier.

Chandra, Tanya & Aggarwal, Rohit. (2023). A Narrative Review of Acthar Gel for the Treatment of Myositis. Rheumatology and therapy. 10. 10.1007/s40744-023-00545-1.

Osmosis & Geeky Medics. (2022, May 12). Pathophysiology of polymyositis [Video]. YouTube. https://www.youtube.com/watch?v=yw87XQWXTPo&ab_channel=osmosisandgeekymedicscore

Sarwar A, Dydyk AM, Jatwani S. Polymyositis. In: StatPearls. StatPearls Publishing, Treasure Island (FL); 2023. PMID: 33085276.

Seetharaman, M., MD. (n.d.). Polymyositis Treatment & management: approach considerations, extramuscular manifestations of polymyositis, inpatient and outpatient care. https://emedicine.medscape.com/article/335925-treatment?form=fpf

1. Corticosteroids

   • Prednisone: The first-line treatment typically involves high doses of oral prednisone to reduce inflammation. Dosage is often started high and then gradually tapered based on patient response and side effects.

2. Immunosuppressive Agents

   • Azathioprine (Imuran): Often used in combination with corticosteroids to help reduce steroid dosage and manage symptoms.

   • Methotrexate: Another common immunosuppressant used to control inflammation and reduce corticosteroid dependency.

   • Mycophenolate mofetil (CellCept): An alternative for patients who do not respond well to azathioprine or methotrexate.

3. Biologic Agents

   • Rituximab (Rituxan): Used in refractory cases where patients do not respond to standard therapies. It targets B cells, a type of immune cell involved in the inflammatory process.

4. Intravenous Immunoglobulin (IVIG)

   • IVIG is used for severe or resistant cases. It can help modulate the immune system and reduce muscle inflammation.

Non-Medical Treatments

1. Physical Therapy

   • Customized exercise programs designed by a physical therapist to improve muscle strength, flexibility, and endurance without overexerting the muscles.

2. Occupational Therapy

   • Assistance with daily activities and adaptive strategies to maintain independence and quality of life.

3. Speech Therapy

   • For patients experiencing difficulty swallowing or speaking due to muscle weakness, a speech therapist can provide exercises and strategies to improve these functions.

4. Diet and Nutrition

   • A balanced diet rich in protein to support muscle repair and overall health. Nutritional counseling may be needed to address swallowing difficulties or other dietary restrictions.

5. Regular Monitoring and Follow-Up

   • Regular follow-up with a rheumatologist or a specialist in neuromuscular diseases to monitor disease progression and treatment response. This includes routine blood tests to check muscle enzyme levels (e.g., creatine kinase), as well as periodic muscle strength evaluations and lung function tests if respiratory muscles are affected.

Lifestyle Modifications

1. Rest and Activity Balance

   • Balancing rest with physical activity to avoid overexertion while staying active enough to maintain muscle strength.

2. Avoiding Triggers

   • Identifying and avoiding potential triggers that may exacerbate symptoms, such as certain medications, infections, or stress.

Experimental Treatments

• Stem Cell Therapy and Other Emerging Therapies

  • Ongoing research is exploring the use of stem cell therapy and other innovative treatments. Participation in clinical trials may be an option for some patients.

Supportive Care

1. Support Groups

   • Joining support groups for individuals with polymyositis can provide emotional support, practical advice, and a sense of community.

2. Mental Health Support

   • Addressing mental health is crucial, as chronic illnesses can be associated with anxiety and depression. Counseling or therapy may be beneficial.

Image 1: The exact cause of polymyositis is unclear, but it's believed to involve the immune system. Muscle fibers start showing more MHC class 1 antigens than usual. CD8 T cells from the immune system then move into the muscle tissue. When these CD8 T cells find and bind to the matching MHC-1 antigens on the muscle fibers, they get activated and release substances called perforin and granzyme. These substances cause the muscle fibers to die (Chandra et al, 2023).

When examining the muscle tissue under a microscope, we can see the inflammation is mostly within individual muscle fibers. These muscle fibers, although sometimes appearing normal, are invaded by CD8+ T cells as mentioned above. The affected muscles often show a mix of muscle fiber damage, including degeneration, necrosis, regeneration, and atrophy, but in a scattered, rather than a patterned, distribution (Kumar V. et al, 2020).

1. Blood Tests: 

• Complete Blood Count (CBC): May show elevated lymphocyte count and thrombocytosis. 

• Erythrocyte Sedimentation Rate (ESR): Often elevated due to chronic inflammation. 

• Serum Creatine Kinase (CK): Significantly elevated (up to 50 times normal), indicating muscle damage. 

2. Antibody Testing: 

• Antinuclear Antibody (ANA): Positive in about 33% of cases. 

• Specific Antibodies: Anti-signal recognition particle (SRP) and anti-aminoacyl tRNA synthetases (ARS) for polymyositis and anti-synthetase syndrome; anti-HMGCR for statin-induced polymyositis. 

3. Electromyography (EMG): 

• Abnormal findings such as varying amplitude and velocity of action potentials and fibrillation potentials due to membrane irritability. 

4. Imaging: 

• MRI: Used to locate muscle damage and guide biopsy. Whole-body MRI is significant for diagnosing the exact damaged area. 

• CT Scan and Ultrasonography: Help locate muscle damage and diagnose underlying malignancy. 

5. Biopsy: 

• MRI or EMG Guided Biopsy: Shows perivascular and endomysial mononuclear infiltrates and areas of necrosis. 

6. Additional Tests: 

• Barium Swallow: For patients with dysphagia. 

• Pulmonary Function Tests (PFTs): If lung disease is suspected. 

• EKG and Echocardiography: To assess potential cardiomyocyte damage. 

The patient, a 61 year old male, arrived to the ER with a 3 week history of generalized weakness and dysphagia of solids . Upon physical examination he showed proximal limb weakness .

Laboratory testing showed elevated leukocytes, but there wasn’t an apparent source of infection. This can lead us to start thinking about an inflammatory disease. Tumor markers were found to be elevated, but after a CT scan, there wasn’t evidence of any malignancy.

Elevated aspartate transaminase (AST), alanine transaminase (ALT), and creatine phosphokinase (CK) were found and this finding can already lead us to start thinking about a muscle wasting syndrome, mainly due to the elevated AST and CK.

Viral panels were performed and were negative. But this was important to perform because viral infections have been related to the development of these idiopathic inflammatory myopathies.

After 3 days in the hospital, symptoms worsened due to mismanagementl; so a neuromuscular disease was suspected. Lumbar punture showed CSF values within normal parameters. Nerve conduction velocities showed reduced amplitude in compound muscle action potential and nerve conduction faiure consistent with axonal polyneuropathy. This could have been associated with the diabetes and not necessarily due to the myopathy.

Electromyography results were not consistent with a demyelinating polyneuropathy; but regardless, the patient was treated with IV immunoglobulin and no clinical improvements were made. The thought process behind this treatment might have been that if autoantobodies were causing the inflammatory response, IVIG contains antibodies that can neutralize pathogenic autoantobodies.

After that the patient developed cardiac insuficientcy. The cardiac symptoms developed by the patients could have been due to respiratory insuficiency causing an ischemic attack in the heart. This can happen because of oropharyngeal muscle weakness; which is also what leads to dysphagia.

An autoimmune disease was suspected and antobodies were requested. Complement C3 was decreased and anti-signal recognition particles were positive. A decreased C3 suggest that C3 protein is being consumed perhaps by an inflammatory process. Anto-SRP are related to inflammatory myopathies. So an inflammatory myopathy was suspected and patient was treated with rituximab, a monoclonal antobody that targets CD20, depleting B cells and halting the effect of the adaptive immune response

A muscle biopsy was taken and infiltraiton of mononuclear and polymorphonuclear cells in the endomysium was observed; indicative of polymyositis.

Unfortunately, the patient developed an infection which eventually lead to a septic shock and he died.