Hereditary alpha-tryptasemia: A case series including omalizumab treatment outcomes

Hereditary alpha-tryptasemia (HαT) is an autosomal-dominant trait caused by increased tryptase alpha/beta 1 gene ( TPSAB1 ) copy number, resulting in elevated basal serum tryptase levels and variable clinical expression. Despite the association with anaphylaxis and mediator-related symptoms, risk stratification and management remain challenging. To describe the phenotypic spectrum of HαT in a single-center case series and assess omalizumab’s role in symptom control, we retrospectively analyzed five patients with confirmed HαT. Demographics, clinical data, and outcomes were recorded. Conventional therapy refractoriness was defined after ≥3 months. Efficacy was assessed at 2 months for cromoglicate and 3 to 6 months for omalizumab. All patients had persistently elevated basal serum tryptase (14–38 μg/L) and increased TPSAB1 copy number (3 α-tryptase copies). Clinical expression ranged from recurrent pruritus (n = 2) to hymenoptera venom–induced anaphylaxis (n = 1) and recurrent anaphylaxis with chronic spontaneous urticaria and multiple drug hypersensitivity (n = 2). Standard antihistamines and leukotriene antagonists provided insufficient control in two patients; omalizumab (300–600 mg every 3–4 weeks), however, led to sustained remission of urticaria and prevention of further anaphylaxis. Additionally, venom immunotherapy was effective in the patient with hymenoptera venom allergy. All patients and relatives at risk were referred for genetic counseling. This series illustrates the heterogeneous presentation of HαT, ranging from pruritus to severe systemic reactions. Overall, our findings support emerging evidence that omalizumab may provide effective symptomatic control in selected patients, though its role remains adjunctive to conventional antimediator therapy rather than disease-modifying. Larger prospective studies are needed to refine risk stratification and therapeutic strategies.