IgE-Mediated Reaction to Levamisole: Evaluation of a Patient With Severe Anaphylaxis

Levamisole has been used as adjuvant immunomodulatory therapy for certain conditions such as amyotrophic lateral sclerosis (ALS). We present a case of a 70-year-old man with ALS who was started on levamisole with adequate response. Within 10 days of treatment, he developed a maculopapular non-pruritic rash on his extremities, and the medication was discontinued. However, two days later, he developed angioedema of the face and hands, urticaria in the extremities and torso, and throat closing sensation that was successfully treated in the emergency department with epinephrine, systemic corticosteroids, and antihistamines. Eight hours later, he presented with recurrent facial angioedema. He was transferred to the ICU and received two more doses of epinephrine and intravenous methylprednisolone. The patient fully recovered within 72 hours and was discharged with the indication to avoid levamisole. One month after the reaction, skin tests (prick and intradermal) with 10-fold dilutions of 550 mg/mL levamisole were positive at a concentration of 55 mg/mL (1:10 dilution). Since the patient developed anaphylaxis and tested positive for levamisole on intradermal testing, and after discussing the options with him, we decided to advise against using this medication since the benefits did not outweigh the risks of administration. This case highlights that IgE-mediated reactions to levamisole, while rare, can occur and be life-threatening. Shared decision-making should be done between patients and physicians after open, evidence-based discussions.