A case study recently published in Allergologia et Immunopathologia showed that among patients with systemic mastocytosis (SM), an accurate diagnosis of hymenoptera venom allergy (HVA) is important, and tests like the Spanish Network on Mastocytosis (REMA) score can help diagnose SM and determine specific allergens.
The researchers described the case study of 48-year-old male gardener from Barcelona, Spain, who experienced an anaphylactic reaction following several wasp stings.
Hymenoptera venom allergy more severe in SM patients
Patients with SM can experience potentially severe anaphylactic reactions. In most individuals, hymenoptera stings cause only minor inflammation and local reactions, including itching, swelling and pain. In the SM patient population, however, the sting of hymenoptera is one of the common triggers of anaphylaxis. In such situations, obtaining the Spanish Network on Mastocytosis (REMA) score can be used to evaluate a person’s risk for SM.
HVA is defined as an “immunglobulin E mediated reaction caused by sensitization to one or more venom allergens.” A diagnosis of HVA is typically based on a clinical history suggestive of the condition, along with confirmation of venom IgE sensitization via skin testing or in vitro tests. The use of venom immunotherapy (VIT) is safe and effective for the reduction of subsequent systemic reactions. Patients with SM require the lifelong administration of VIT, following an individualized diagnosis on a person-by-person basis.
The patient discussed in the case report was referred to the allergy department of a hospital six months after he experienced an anaphylactic reaction following several wasp stings. The event took place in an area in which the presence of both Vespula and Polistes dominula vespids are recognized. The culprit vespid, however, could not be identified.
Immediately following the sting, the patient experienced a large local reaction, along with nasal obstruction, dyspnea and stridor. There was no additional cutaneous involvement. He experienced a complete recovery in the emergency department after receiving treatment with antihistamines and corticosteroids.
How additional tests helped identify a specific allergen
The patient underwent a complete allergy workup with skin tests and in vitro testing. His REMA score was four, which is highly indicative of clonality. Based on a bone marrow biopsy, atypical mast cells with an aberrant phenotype were observed, although the KIT D816V mutation was not present.
Ultimately, the patient was diagnosed with indolent SM (ISM), and an allergy to both Polistes dominula and Vespula species venom was confirmed. Because MD was unable to differentiate between a genuine double sensitization and venom cross-reactivity between the two vespids, a CAP-inhibition assay was implemented.
“In spite of the strong association between ISMs and HVA, the former continues to be underdiagnosed,” the authors noted. “In cases of anaphylactic reactions (especially without skin involvement) and high levels of basal serum tryptase, a REMA score should always be performed to assess the probability of a [mast cell] disorder,” they concluded.
