Anaphylaxis to protamine masquerading as an insulin allergy

Area of Science:

• Immunology
• Endocrinology
• Pharmacology

Background:

• Insulin allergy is a rare condition.
• Protamine sulfate is used as a protamine-containing agent in some insulin formulations.

Observation:

• A 62-year-old man presented with symptoms of insulin allergy, including urticaria, angioedema, and hypotension, after receiving specific insulin preparations.
• The patient had a history of anaphylactic shock following protamine sulfate administration.
• Skin testing and RAST tests indicated a strong hypersensitivity to protamine sulfate, with negligible insulin-specific antibodies.

Findings:

• The patient's allergic reactions were confirmed to be Type I hypersensitivity to protamine sulfate, not to the insulin component.
• Lente insulin, a protamine-free preparation, was used successfully for treatment, preventing further adverse events.

Implications:

• This case highlights the importance of considering protamine sulfate hypersensitivity in patients experiencing allergic reactions to certain insulin formulations.
• Accurate diagnosis through specific allergy testing is crucial for appropriate patient management and preventing severe allergic responses.
• Identifying and avoiding protamine-containing insulins can effectively manage patients with protamine sulfate allergy.