Venom evaluation in mastocytosis patient
Question:
12/5/2019
42 year-old man recently evaluated, with h/o anaphylactic shock X2 (2015 and 8/2019). Based on presentation evaluated for mastocytosis- tryptase 30 X 2. Bone marrow consistent with systemic mastocytosis and has D816V KIT mutation. RAST + to YJ only at reference lab where negative it is < 0.35. Assay at Johns Hopkins shows + for YJ at 1.0, and + for WFH and Polistes wasp at 0.12 (Negative is < 0.1) He will be coming in for skin testing to venoms other than yellow jacket. Questions:
1. If skin testing is negative to WFH and/or wasp, would you include them in his immunotherapy program?
2. What venom concentration dose would you start immunotherapy at?
3. Will premedicate for venom injections with H1 and H2 antagonist. Any other recommendations?
Answer:
1) Yes, include each venom that is positive, whether by sIgE or by skin testing.
2) We use either standard conventional protocol or modified RUSH with pre-medication. We do not adjust start dose down, unless there is a systemic reaction. If the patient reacts at initial dosing, we adjust down a log. If the patient continues to react, then we consider RUSH or modified RUSH with premedication. If the patient continues to react, then consider “off-label” pretreatment with omalizumab.
3) Premedication with H1 and H2 has been shown to decrease local reactions, but does not decrease the risk of systemic reaction, nor does it mask early signs of systemic reaction.
You may find this reference helpful.
Bonadonna P, Gonzalez-de-Olano D, Zanotti R. Venom Immunotherapy in Patients with Clonal Mast Cell Disorders: Efficacy, Safety, and Practical Considerations. J Allergy Clin Immunol Pract 2013; 1:474-8.
Respectfully submitted
Jeffrey G Demain, MD, FAAAAI