Pembrolizumab-induced hypothyreosis and subcutaneous bleeding

Area of Science:

• Oncology
• Endocrinology
• Hematology

Background:

• Pembrolizumab, an immune checkpoint inhibitor, is used for non-small cell lung carcinoma.
• Hypothyroidism is a known adverse event of pembrolizumab therapy.

Observation:

• A patient developed severe hypothyroidism and spontaneous subcutaneous hematomas during pembrolizumab treatment.
• The hypothyroidism followed a transient phase of subclinical hyperthyroidism.

Findings:

• Hematological disorders including acquired von Willebrand syndrome, acquired hemophilia A, dysfibrinogenemia, fibrinolysis activation, and thrombocytopathy were ruled out.
• Markers for secondary autoimmune disease and myositis were also excluded.
• Subcutaneous hematomas resolved with intensified thyroid hormone replacement therapy, despite continued pembrolizumab administration.

Implications:

• This case establishes a causal relationship between pembrolizumab-induced hypothyroidism and subcutaneous hematomas.
• Highlights the importance of monitoring thyroid function and managing endocrine adverse events during immunotherapy.
• Suggests that prompt endocrine management can mitigate serious complications associated with immune checkpoint inhibitors.