RESUMO
BTK deficiency is a primary immunodeficiency disease characterized by the absence of circulating B cells and agammaglobulinemia. While recurrent bacterial infections are the most common manifestations, symptoms of allergy and asthma are rare. We present the case of a 7-year-old boy who presented with asthma symptoms, allergic rhinitis, and severe papular urticaria. He had a positive skin prick test to aeroallergens and food allergens. However, further laboratory tests revealed a low number of B cells and decreased serum levels of all immunoglobulin isotypes. Molecular analysis revealed a mutation in the BTK gene. Although patients with BTK deficiency seem to be protected from atopy, our patient had allergic symptoms suggesting a bias toward a type 2 helper T cell pattern in this case. Primary antibody deficiency should be considered in the differential diagnosis of pediatric allergy and asthma when respiratory infection persists despite appropriate treatment.