A young Caucasian female with severe bronchial asthma and Alpha1-antitrypsin (AAT) deficiency, MZ phenotype, experienced a quick and severe limitation of her physical capacity, which negatively affected her psychological state and social life, though she was under a strong antiasthmatic treatment. Given her declining health status and the significant chronic corticoid administration-related side-effects (including high reduction of muscle mass and bone density), a clinical trial with commercial intravenous AAT was proposed by the patient's doctors, and accepted by the Spanish Ministry of Health, although it this therapy was not approved for MZ phenotypes yet. This new therapy quickly stopped lung function decline rate, dramatically reduced the number of hospital admissions of the patient, suppressed the oral administration of prednisone, reversed the corticosteroid-related health adverse effects, significantly improving her quality of life. Thus, although AAT replacement therapy is not approved nor indicated for the treatment of bronchial asthma in MZ patients, its favourable effects observed in this isolated case support the hypothesis that bronchial asthma could be due to pathogenic mechanisms related to a protease-antiprotease imbalance, what which could open new perspectives for future research on the field.