WHAT APPEARS TO BE POSSIBLE CARCINOID IS IN FACT MAST CELL ACTIVATION SYNDROME

Abstract

Introduction Mast cell activation syndrome (MCAS) has been increasingly used to define patients with episodic systemic symptoms secondary to mast cell activation that do not fit the criteria for systemic mastocytosis or monoclonal mast cell activation syndrome. Here we present a patient with MCAS with laboratory features of carcinoid syndrome. Case Description A 54-year old Caucasian female with allergic rhinitis, urticaria, flushing with and without eating, fogginess, polycythemia, and Graves disease s/p total thyroidectomy presented to establish care. Labs revealed elevated tryptase of 18 ng/mL, and an elevated 24-hour urine prostaglandin D2 of 388 ng. Bone marrow biopsy findings were normal. Serum 5-HIAA and chromogranin A were normal. However, her 24-hour urine 5-HIAA was persistently elevated. Further work up failed to reveal findings consistent with carcinoid syndrome, including negative chest and abdominal scans. Given a convincing history of venom hypersensitivity, skin tests were performed revealing positives to honeybee, wasp and mixed venom. Patient was started on oral cromolyn with improvement in her flushing symptoms. She initially experienced diarrhea and abdominal cramping which has now resolved. She has been doing well with immunotherapy for allergic rhinitis, and is currently waiting to start venom immunotherapy. Discussion Although our patient's work up revealed persistently elevated urine 5-HIAA consistent with carcinoid syndrome, further work up revealed a picture more consistent with mast cell disorder. This case emphasizes the importance of considering MCAS even in patients with laboratory markers seen in carcinoid syndrome. Mast cell activation syndrome (MCAS) has been increasingly used to define patients with episodic systemic symptoms secondary to mast cell activation that do not fit the criteria for systemic mastocytosis or monoclonal mast cell activation syndrome. Here we present a patient with MCAS with laboratory features of carcinoid syndrome. A 54-year old Caucasian female with allergic rhinitis, urticaria, flushing with and without eating, fogginess, polycythemia, and Graves disease s/p total thyroidectomy presented to establish care. Labs revealed elevated tryptase of 18 ng/mL, and an elevated 24-hour urine prostaglandin D2 of 388 ng. Bone marrow biopsy findings were normal. Serum 5-HIAA and chromogranin A were normal. However, her 24-hour urine 5-HIAA was persistently elevated. Further work up failed to reveal findings consistent with carcinoid syndrome, including negative chest and abdominal scans. Given a convincing history of venom hypersensitivity, skin tests were performed revealing positives to honeybee, wasp and mixed venom. Patient was started on oral cromolyn with improvement in her flushing symptoms. She initially experienced diarrhea and abdominal cramping which has now resolved. She has been doing well with immunotherapy for allergic rhinitis, and is currently waiting to start venom immunotherapy. Although our patient's work up revealed persistently elevated urine 5-HIAA consistent with carcinoid syndrome, further work up revealed a picture more consistent with mast cell disorder. This case emphasizes the importance of considering MCAS even in patients with laboratory markers seen in carcinoid syndrome.