Insectenallergie en Systemische Mastocytose: Natuurlijk beloop, Diagnose en Veiligheid en Effectiviteit van Immunotherapie

Background: About 30% of all systemic mastocytosis (SM) patients suffer from insect venom allergy (IVA). These patients develop severe (life-threatening) anaphylactic reactions. Re-sting reaction rate in the normal IVA population varies from 20-70%, depending on the severity of the sting reaction. Recommended treatment for IVA is venom immunotherapy (VIT). The protection rate of VIT in patients without SM is >95%, whereas the protection rate is about 70% in SM patients. VIT was not applied for SM patients in the University Medical Centre of Groningen, because of alleged ineffectiveness and side-effects. This untreated population gives us the opportunity to evaluate epidemiology, quality of life and natural history of IVA in SM, and we will be able to determine the baseline situation before starting VIT. VIT was reintroduced in the UMCG because of recent publications. Diagnosis of IVA as an indication for VIT was difficult because of low total and specific IgE and low sensitivity of intradermale skintest. Therefore we decided to evaluate the diagnostic value of these tests and the basophil activation test (BAT) in SM. We adopted the re-introduction of VIT to evaluate side-effects and effectivity. Methods: 168 adult patients with (suspected) indolent SM (ISM) were sent a questionnaire concerning IVA evaluating frequency and severity of sting reactions and the Vespid Quality of Life Questionnaire adjusted for SM. Only patients who fulfilled WHO criteria for ISM were included. Biochemical, histological and clinical data were analyzed. Seventeen SM patients who had a convincing history of IVA were tested with specific serologic assays (CAP-RAST), skintest en BAT; in ten negative controles we did the same testing. During VIT side-effects were written down carefully. Serologic and immunologic tests were performed before starting VIT and after reaching maintenance dose. Results: A total of 132 patients fulfilled inclusion criteria (47 men and 85 women, mean age 52,0 (SD±11,3)). Of patients stung during adulthood (n=93), 57% experienced a systemic reaction at least once: 76% of patients suffered from a Mueller grade 4 reaction, of which 78% lost consciousness. When stung again after the first sting reaction, 76% reacted on first re-sting (n=25). When re-stung at least twice, all patients reacted (n=9). The re-sting reactions were severe in 74%. In SM, IVA influences the quality of life in a negative way (1,57 vs. 3,07; p