D2.100 - Carcinoid Crisis Mimicking IgE-Mediated Hypersensitivity Reaction During Peptide Receptor Radionuclide Therapy (PRRT): A Diagnostic Dilemma

Carcinoid crisis is a rare but life-threatening complication of neuroendocrine tumors (NETs) that can be precipitated during peptide receptor radionuclide therapy (PRRT). Differentiating it from drug hypersensitivity reactions is critical for appropriate management.

We present a 42-year-old female with a confirmed diagnosis of metastatic small bowel neuroendocrine tumor (NET), who had shown progressive disease despite treatment with lanreotid (a somatostatin analog), necessitating a transition to Peptide Receptor Radionuclide Therapy (PRRT). She was admitted for her first cycle, the standard protocol was followed, which included a continuous amino acid infusion (L-lysine and L-arginine) initiated prior to the PRRT to provide renal protection and continued during and after the PRRT. Three hours after the PRRT infusion, she developed acute flushing, dizziness, diarrhea, and an episode of vomiting. The clinical picture quickly escalated to include hypotension, tachycardia, and oxygen desaturation. The initial assessment suggested a severe IgE-mediated hypersensitivity reaction to amino acid, leading to the administration of diphenhydramine and hydrocortisone but resulted in minimal improvement. The patient required boluses of fluid resuscitation and intramuscular epinephrine. While her blood pressure eventually stabilized, the epinephrine exacerbated her tachycardia, precipitating a transient cardiac arrhythmia. Following the stabilization of the patient, and due to the temporal association between the reaction and the amino acid infusion, the infusion was terminated, and the patient was labeled with an allergy to amino acids. This label posed a significant clinical hurdle, as the patient required subsequent PRRT cycles to manage her malignancy. She was referred to a drug allergy clinic for a formal evaluation. After a comprehensive evaluation of the index reaction, underlying medical condition, and risk factors, her reaction was consistant with PRRT-induced carcinoid crisis rather than a hypersensitivity reaction to amino acid infusion. Recognizing the pathophysiology of carcinoid crisis, patient underwent subsequent cycles with preventive measures. She tolerated subsequent cycles with no adverse reactions. PRRT-induced carcinoid crisis can mimic drug hypersensitivity, leading to potential mislabeling and delayed treatment. Recognition of clinical patterns, risk factors, and timely intervention with supportive measures is essential for patient safety. This case highlights the importance of differentiating carcinoid crisis from drug allergy in NET patients undergoing PRRT, to ensure accurate diagnosis and prevent inappropriate therapy cessation.