Late-onset anaphylactic reactions following i.v. cyclophosphamide pulse in a patient with systemic sclerosis and systemic lupus erythematosus overlap syndrome.

Late-onset anaphylactic reaction is a rare adverse effect of i.v. cyclophosphamide pulse (IVCY), which is caused by cyclophosphamide metabolites. We herein report a case of scleroderma and lupus overlap syndrome who developed anaphylactic reactions 3 h to 4 days after IVCY. Long time lapses between IVCY and appearance of symptoms are compatible with type I hypersensitivity to cyclophosphamide metabolites, appearing as late-onset anaphylactic reaction. Albeit unusual, this is an important anaphylactic reaction to be aware of following IVCY.