A CASE OF IDIOPATHIC ANAPHYLAXIS: A 4-YEAR ODYSSEY

Abstract

Introduction Idiopathic anaphylaxis is rare and only diagnosed after a thorough evaluation. Case Description A 43-year-old man presented to the allergy clinic after four years of recurrent facial flushing, truncal wheals, abdominal cramps, diarrhea, difficulty breathing, palpitations, lightheadedness, and fainting that rapidly resolved after epinephrine, antihistamines, and corticosteroids. Prior autoimmune panel, serum tryptase, urine histamine and catecholamines, and skin prick testing for food and inhalants failed to identify an etiology. He was diagnosed with idiopathic anaphylaxis and treated with fexofenadine, loratadine, and epinephrine autoinjector. Physical examination revealed facial and upper-chest flushing (Image). Initial work-up showed normal anti-alpha-gal IgE, VIP, and tryptase levels at baseline and during attacks. C-KIT Asp816Val gene mutation analysis was negative. Bone marrow biopsy showed no mast cells. 24hr urine catecholamine levels were unremarkable, but 5-HIAA levels were elevated to 8.5 and 9.5mg/24hr on two separate samples (normal ≤8mg/24hr). Serum chromogranin A levels were high. Gallium 68-DOTATATE PET-CT, bronchoscopy, and EGD/colonoscopy failed to show a tumor. Somatostatin analogs were initiated with clinically significant improvement. Discussion Carcinoid syndrome mimics anaphylaxis. It occurs in 20% of neuroendocrine tumors originating from the gastrointestinal or respiratory tract and their systemic release of vasoactive peptides; 24hr urinary 5-HIAA is specific but poorly-sensitive. Tumor localization can be attempted with CT or radiolabeled somatostatin analogs imaging. Upper/lower endoscopies and bronchoscopy may be considered with negative or inconclusive imaging results. As in our patient, a tumor cannot be localized in 13% of patients. Somatostatin analogs are the first-line treatment in patients with unresectable tumors. Idiopathic anaphylaxis is rare and only diagnosed after a thorough evaluation. A 43-year-old man presented to the allergy clinic after four years of recurrent facial flushing, truncal wheals, abdominal cramps, diarrhea, difficulty breathing, palpitations, lightheadedness, and fainting that rapidly resolved after epinephrine, antihistamines, and corticosteroids. Prior autoimmune panel, serum tryptase, urine histamine and catecholamines, and skin prick testing for food and inhalants failed to identify an etiology. He was diagnosed with idiopathic anaphylaxis and treated with fexofenadine, loratadine, and epinephrine autoinjector. Physical examination revealed facial and upper-chest flushing (Image). Initial work-up showed normal anti-alpha-gal IgE, VIP, and tryptase levels at baseline and during attacks. C-KIT Asp816Val gene mutation analysis was negative. Bone marrow biopsy showed no mast cells. 24hr urine catecholamine levels were unremarkable, but 5-HIAA levels were elevated to 8.5 and 9.5mg/24hr on two separate samples (normal ≤8mg/24hr). Serum chromogranin A levels were high. Gallium 68-DOTATATE PET-CT, bronchoscopy, and EGD/colonoscopy failed to show a tumor. Somatostatin analogs were initiated with clinically significant improvement. Carcinoid syndrome mimics anaphylaxis. It occurs in 20% of neuroendocrine tumors originating from the gastrointestinal or respiratory tract and their systemic release of vasoactive peptides; 24hr urinary 5-HIAA is specific but poorly-sensitive. Tumor localization can be attempted with CT or radiolabeled somatostatin analogs imaging. Upper/lower endoscopies and bronchoscopy may be considered with negative or inconclusive imaging results. As in our patient, a tumor cannot be localized in 13% of patients. Somatostatin analogs are the first-line treatment in patients with unresectable tumors.