Background: Patent blue is a blue dye commonly used for sentinel node detection in the management of melanoma and breast cancer. Immediate hypersensitivity reactions to patent blue such as blue urticaria, bronchospasm or anaphylactic shock are not rare, being seen in 0.8 to 2.8% of patent blue-treated patients.
Patients and methods: We report three cases of anaphylactic shock and two cases of urticaria developed after injection of patent blue in the context of sentinel node detection in breast cancer patients. Immediately after surgery, two patients developed generalized urticaria followed by circulatory collapse requiring resuscitation. The third patient presented massive anaphylactic shock without cutaneous or respiratory signs. Blue urticaria without haemodynamic disturbance was seen in the latter two patients. Prick tests using patent blue were positive for the three patients with positive intradermal reactions (1/10,000 dilution) in all patients.
Discussion: These observations underline the severity of patent blue-induced shocks with delayed onset, since they are often observed at the end of surgery. While the mode of sensitization is poorly understood, food and textile dyes are thought to play a role. Skin prick tests provide a simple and reliable method of diagnosing these events. There is a real risk of late anaphylactic shock during sentinel node detection using patent blue and discussion is needed concerning alternative methods of sentinel node detection.