Steroid myopathy in connective tissue disease

Area of Science:

• Rheumatology
• Neurology
• Clinical Pharmacology

Background:

• High-dose corticosteroid therapy is frequently used for inflammatory and autoimmune conditions.
• Muscle weakness is a potential side effect of prolonged corticosteroid use, but its diagnosis can be challenging.
• Differentiating steroid-induced myopathy from disease flares in connective tissue disorders is clinically important.

Purpose of the Study:

• To investigate the clinical presentation and diagnostic markers of steroid myopathy in patients with autoimmune diseases.
• To evaluate the utility of muscle enzymes and urinary creatine excretion in diagnosing and monitoring steroid myopathy.
• To assess the effectiveness of clinical and laboratory methods in managing steroid myopathy without muscle biopsy.

Main Methods:

• Studied eight female patients with polymyositis, systemic lupus erythematosus, rheumatoid arthritis, or shoulder-hand syndrome experiencing weakness during high-dose prednisone therapy.
• Utilized serial functional and manual muscle testing.
• Measured serum glutamic oxaloacetic transaminase (SGOT), creatine phosphokinase (CPK), and serum aldolase levels.
• Assessed urinary creatine excretion.

Main Results:

• All patients exhibited weakness, predominantly in the pelvic girdle, with normal serum muscle enzyme levels.
• Urinary creatine excretion was consistently increased in all patients, serving as a sensitive indicator.
• Serial urinary creatine excretion and serum enzyme studies helped differentiate steroid myopathy from disease flares.

Conclusions:

• Steroid myopathy presents with characteristic muscle weakness and normal serum muscle enzymes.
• Increased urinary creatine excretion is a reliable biomarker for diagnosing and monitoring steroid myopathy.
• Clinical and laboratory assessments, particularly urinary creatine levels, allow for effective diagnosis and management, obviating the need for muscle biopsy.