Anaphylactic shock to fresh-frozen plasma inactivated with methylene blue

BACKGROUND: Methylene blue allergy is a well-known entity associated with food or lymph node location. Inactivation of viruses by methylene blue in fresh-frozen plasma (FFP-MB) has been recently introduced in France after many years of use in other parts of Europe. CASE REPORT: We describe here two anaphylactic shock reactions occurring during FFP-MB infusion in patients after cardiac surgery. The follow-up was favorable using epinephrine infusion in one patient and extracorporeal circulatory assistance in the other. RESULTS: The allergy was suspected based on the following arguments: chronology of the event, absence of other allergen infused to patients, and an associated symptom (generalized rash). Methylene blue allergy was documented by prick tests and/or intradermal reactions with methylene blue and patent blue. Additional allergic tests with basophil activation tests confirm the role of the dye in the anaphylactic reaction. CONCLUSION: These two cases questioned the safety of FFP-MB.