Dermatomyositis (DM) and Polymyositis (PM): Pathogenesis and clinical findings

Elevated Antinuclear Antibodies: Anti-Jo-1, Anti-OJ, Anti-Mi2, Anti-SRP, Anti-EJ, Anti-PL12, Anti-PL7

Demographics:

 - F:M, 2:1

 - Bimodal age distribution:

     - Juvenile: 7 years of age (mean)

     - Adult: 52 years of age (mean)

Perivascular, Capillary necrosis -> 

   - These processes occur in the skin on the dorsum of the hands, forming hyperkeratotic flat red papules -> Gottron Papules

   - These processes occur in the upper & lower eyelids, causing red-purple discoloration +/- swelling -> Heliotrope Rash



 - Dysphagia

 - Aspiration, respiratory compromise

 - Atrioventricular defects, tachyarrhythmias, dilated cardiomyopathy

 - Elevation of muscle enzyme levels in serum: Creatinine kinase (CK), lactate dehydrogenase (LD), aldolase, aspartate aminotransferase (AST), and alanine aminotransferase (ALT)

 - Muscle Biopsy Findings: Muscle necrosis, fiber regeneration, diffuse CD8+ T lymphocytes infiltrates

 - Bilateral Muscle Weakness: Subacute development, primarily deltoids and hip flexors affected



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