Myxoedema coma caused by immunotherapy-related thyroiditis and enteritis

Area of Science:

• Immunology
• Endocrinology
• Oncology

Background:

• Immune checkpoint inhibitors (ICIs) are widely used for cancer treatment.
• Thyroid dysfunction is a common immune-related adverse event (irAE) associated with ICIs.
• While usually mild, ICI-induced thyroid dysfunction can rarely lead to life-threatening myxoedema coma.

Purpose of the Study:

• To report a rare case of myxoedema coma.
• To highlight the dual irAEs contributing to the complication: painless thyroiditis and enterocolitis.
• To emphasize the diagnostic and management challenges of ICI-related endocrinopathies.

Main Methods:

• Case presentation of a patient with stage four malignant melanoma treated with CTLA-4 and PD-1 inhibitors.
• Detailed clinical course including development of hypothyroidism, enteritis, and myxoedema coma.
• Diagnostic workup including thyroid function tests and thyroxine absorption test.
• Treatment with intravenous triiodothyronine and methylprednisolone.

Main Results:

• The patient developed profound hypothyroidism and myxoedema coma due to thyroxine malabsorption secondary to ICI-induced enteritis.
• Intravenous T3 improved her clinical status, but enteritis was refractory to steroids.
• Thyroxine absorption tests confirmed persistent malabsorption, preventing oral thyroxine reinitiation.
• The patient's underlying malignancy progressed, leading to her death.

Conclusions:

• Myxoedema coma is a rare but severe ICI-related endocrinopathy.
• Co-administration of glucocorticoids with thyroid hormone replacement is vital to prevent adrenal crisis.
• Close monitoring of thyroid function tests in patients with hypothyroidism and diarrhea is essential due to malabsorption risk.
• Thyroid function tests and thyroxine absorption tests aid in diagnosing and managing thyroxine malabsorption.