Elevated serum levels of calcitonin gene-related peptide in Hymenoptera sting-induced anaphylaxis

Nonaggressive systemic mastocytosis (SM) without skin lesions associated with insect-induced anaphylaxis shows unique features versus other indolent SM

BACKGROUND

Indolent systemic mastocytosis (ISM) without skin lesions (ISMs(-)) shows a higher prevalence in males, lower serum baseline tryptase levels, and KIT mutation more frequently restricted to bone marrow (BM) mast cells (MCs) than ISM with skin lesions (ISMs(+)). Interestingly, in almost one-half of ISMs(-) patients, MC-mediator release episodes are triggered exclusively by insects.

OBJECTIVE

We aimed to determine the clinical and laboratory features of ISMs(-) associated with insect-induced anaphylaxis (insectISMs(-)) versus other patients with ISM.

METHODS

A total of 335 patients presenting with MC activation syndrome, including 143 insectISMs(-), 72 ISMs(-) triggered by other factors (otherISMs(-)), 56 ISMs(+), and 64 nonclonal MC activation syndrome, were studied.

RESULTS

Compared with otherISMs(-) and ISMs(+) patients, insectISMs(-) cases showed marked male predominance (78% vs 53% and 46%; P < .001), a distinct pattern of MC-related symptoms, and significantly lower median serum baseline tryptase levels (22.4 vs 28.7 and 45.8 μg/L; P ≤ .009). Moreover, insectISMs(-) less frequently presented BM MC aggregates (46% vs 70% and 81%; P ≤ .001), and they systematically showed MC-restricted KIT mutation.

CONCLUSIONS

ISMs(-) patients with anaphylaxis triggered exclusively by insects display clinical and laboratory features that are significantly different from other ISM cases, including other ISMs(-) and ISMs(+) patients, suggesting that they represent a unique subgroup of ISM with a particularly low BM MC burden in the absence of adverse prognostic factors.

Mastocytosis and insect venom allergy: diagnosis, safety and efficacy of venom immunotherapy

The most important causative factor for anaphylaxis in mastocytosis are insect stings. The purpose of this review is to analyse the available data concerning prevalence, diagnosis, safety and effectiveness of venom immunotherapy (VIT) in mastocytosis patients. If data were unclear, authors were contacted personally for further information. Quality of evidence (A: high, B: moderate, C: low and D: very low) and strength of recommendation (strong 1 and weak 2) concerning VIT in mastocytosis patients are assessed according to the Grading of Recommendations Assessment, Development and Evaluation and are marked in square brackets. Results of VIT were described in 117 patients to date. The mean rate of side-effects during treatment in studies published so far is 23.9% (7.6% requiring adrenaline) with an overall protection rate of 72%. Based on the review we conclude that (1) mastocytosis patients have a high risk of severe sting reactions in particular to yellow jacket, (2) VIT could be suggested [2] in mastocytosis, (3) probably should be done life long [2], (4) VIT in mastocytosis is accompanied by a higher frequency of side-effects, so (5) special precautions should be taken into account notably during the built up phase of the therapy [2], (6) VIT is able to reduce systemic reactions, but to a lesser extent compared to the general insect venom allergic population [2], so (7) patients should be warned that the efficacy of VIT might be less than optimal and they should continue carrying two adrenaline auto injectors [2].

Systemic Mastocytosis: Clinical Manifestations and Differential Diagnosis

Mast cells produce symptoms by local and remote effects of mediator release and by their presence in increased numbers in normal tissue and bone marrow, where they damage and impair normal organ function. Moreover, mast cells are long-lived and heterogeneous in their response to secretagogues and to inhibitors of mediator release. Clinicians sorting out the diagnosis of SM on the basis of presenting signs and symptoms continue to have their diagnostic skills challenged because of the rarity of this disorder, the fact that many symptoms of SM are present in more common disorders, and the multiple guises that SM may assume at the time of presentation.

Patients with negative skin tests

PURPOSE OF REVIEW

The aim of this article is to present and discuss the clinical problem of systemic anaphylaxis to Hymenoptera venoms in patients without detectable immunoglobulin E, as it appears in recent literature. Reported at variable frequency in large series of patients undergoing evaluation, systemic anaphylaxis was previously considered to reflect lost sensitization or to involve non-immunoglobulin E mediated mechanisms. Sporadic case-reports drew attention to the fact that severe or even fatal reactions may occur in patients with negative skin tests.

RECENT FINDINGS

A breakthrough article by Golden et al., who performed deliberate stings on skin test negative venom anaphylaxis patients, demonstrated that clinical sensitivity was still present in a subset of these subjects and pointed out to the limitations of present diagnostic methods or reagents. New immunobiochemical methods and highly specific recombinant allergens--when all clinically relevant Hymenoptera venom allergens have been identified, cloned, sequenced and expressed in the proper system--are anticipated to increase the diagnostic yield. Non-specific mechanisms causing anaphylactoid reactions will probably explain some enigmatic, skin test negative radioallergosorbent test negative cases in the future. Occult mastocytosis, predisposing patients to anaphylactoid reactions, has been reported with increasing frequency among skin test negative patients. Lastly, other causes mimicking venom anaphylaxis may on rare occasions contribute to the problem.

SUMMARY

With the present understanding of venom allergy, the practising clinician is not infrequently faced with the dilemma of the skin test negative patient. Once other identifiable causes have been carefully ruled out, referral to a specialized center for deliberate sting-challenges appears in selected cases to be a medically appropriate and ethically justified management approach.