We compared these characteristics of all patients with and without MBL ≤50 ng/mL: age at diagnosis; sex; body mass index (BMI); upper and lower respiratory tract infection; diabetes; autoimmune condition(s); atopy; other allergy; corticosteroid therapy; and subnormal serum levels of IgG subclasses, IgA, and IgM (dichotomous variables). This evidence concerns the gene MBL2 and Recurrent lower respiratory tract infections.