[Hypothyroid myopathy caused by interferon-alpha therapy for chronic hepatitis C]

Area of Science:

• Endocrinology
• Hepatology
• Immunology

Background:

• Hepatitis C virus (HCV) infection is a global health concern.
• Interferon-alpha (IFN-alpha) therapy has been used to treat chronic hepatitis C.
• Autoimmune thyroid diseases are common, but myopathy as a direct consequence of IFN-alpha therapy is rare.

Observation:

• A 59-year-old man developed proximal muscle weakness 1-6 months after starting IFN-alpha therapy for chronic hepatitis C.
• Elevated creatine kinase (CK) and myoglobin levels indicated muscle damage.
• Thyroid function tests revealed hypothyroidism with elevated TSH and decreased free T3/T4 levels.
• High titers of blocking-type TSH receptor antibodies were detected, suggesting an autoimmune process.

Findings:

• The patient was diagnosed with hypothyroid myopathy.
• Muscle weakness and elevated CK levels resolved completely with thyroid hormone replacement therapy.
• Blocking-type TSH receptor antibodies remained elevated even after hypothyroidism resolved.
• Muscle biopsy showed non-specific mild myopathic changes.

Implications:

• IFN-alpha therapy may induce or exacerbate autoimmune thyroid disease in susceptible individuals, potentially by fostering autoreactivity related to HCV infection.
• This case highlights the importance of monitoring thyroid function during IFN-alpha treatment.
• Early diagnosis and treatment of hypothyroid myopathy are crucial for patient recovery.