A case report of atypical anaphylaxis in an immunosuppressed myasthenic patient

Anaphylaxis is a life-threatening systemic hypersensitivity reaction characterized by rapid onset and potential for airway, respiratory, or circulatory compromise. Early recognition and treatment with intramuscular epinephrine are critical to improve outcomes However, atypical or delayed presentations may occur, especially in patients on chronic immunosuppressive therapies such as corticosteroids, which can blunt or delay inflammatory responses. Additionally, patients with autoimmune conditions like myasthenia gravis (MG) present unique diagnostic and therapeutic challenges due to overlapping symptomatology and medication sensitivities We report a case of a 49-year-old male with MG maintained on high-dose weekly prednisone (200 mg) presenting with progressive urticaria, dyspnea, dizziness, and hypotension two days after hot tub exposure. The delayed onset of symptoms, coupled with a muted systemic response likely from chronic steroid use, complicated the recognition of anaphylaxis. Despite administration of multiple doses of antihistamines and intramuscular epinephrine, the patient remained hypotensive and required vasopressor support. He responded to an epinephrine infusion and was stabilized in the critical care unit. This case underscores the diagnostic complexity of anaphylaxis in immunosuppressed individuals. Delayed or incomplete presentations may hinder timely intervention. A high index of suspicion should be maintained for atypical anaphylactic shock in patients with autoimmune disorders on chronic steroids, with early consideration for vasopressor support when IM epinephrine is insufficient.