Anaphylactic Reactions After Discontinuation of Hymenoptera Venom Immunotherapy: A Clonal Mast Cell Disorder Should Be Suspected

J Allergy Clin Immunol Pract. 2018 Jul-Aug;6(4):1368-1372. doi: 10.1016/j.jaip.2017.11.025. Epub 2017 Dec 16.

Abstract

Background: Up to 75% of patients with severe anaphylactic reactions after Hymenoptera sting are at risk of further severe reactions if re-stung. Venom immunotherapy (VIT) is highly effective in protecting individuals with ascertained Hymenoptera venom allergy (HVA) and previous severe reactions. After a 3- to 5-year VIT course, most patients remain protected after VIT discontinuation. Otherwise, a lifelong treatment should be considered in high-risk patients (eg, in mastocytosis). Several case reports evidenced that patients with mastocytosis and HVA, although protected during VIT, can re-experience severe and sometimes fatal reactions after VIT discontinuation.

Objective: To evaluate whether patients who lost protection after VIT discontinuation may suffer from clonal mast cell disorders.

Methods: The survey describes the characteristics of patients who received a full course of VIT for previous severe reactions and who experienced another severe reaction at re-sting after VIT discontinuation. Those with a Red Española de Mastocitosis score of 2 or more or a serum basal tryptase level of more than 25 ng/mL underwent a hematological workup (bone marrow biopsy, KIT mutation, expression of aberrant CD25) and/or skin biopsy.

Results: Nineteen patients (mean age, 56.3 years; 89.5% males) were evaluated. All of them had received at least 4 years of VIT and were protected. After VIT discontinuation they were re-stung and developed, in all but 1 case, severe anaphylactic reactions (12 with loss of consciousness, in the absence of urticaria/angioedema). Eighteen patients (94.7%) had a clonal mast cell disorder, 8 of them with normal tryptase.

Conclusions: Looking at this selected population, we suggest that mastocytosis should be considered in patients developing severe reactions at re-sting after VIT discontinuation and, as a speculation, patients with mastocytosis and HVA should be VIT-treated lifelong.

Keywords: Anaphylaxis; Hymenoptera venom allergy; Re-sting; Systemic mastocytosis; Tryptase.

MeSH terms

  • Allergens / immunology
  • Anaphylaxis / diagnosis*
  • Animals
  • Clone Cells
  • Desensitization, Immunologic / methods*
  • Female
  • Humans
  • Hymenoptera / immunology
  • Hypersensitivity / diagnosis*
  • Insect Bites and Stings / diagnosis*
  • Male
  • Mast Cells / immunology*
  • Mastocytosis / diagnosis*
  • Middle Aged
  • Tryptases / blood
  • Unconsciousness
  • Venoms / immunology
  • Withholding Treatment

Substances

  • Allergens
  • Venoms
  • Tryptases