BACKGROUND Alpha one antitrypsin deficiency is a rare genetic disorder occurring principally in patients with the PiZZ phenotype. This deficiency can lead to pulmonary emphysema which impairs quality of life and which may progress to respiratory failure. The diagnosis is based on the presence of emphysema typically with a basal preponderance and airflow obstruction and is confirmed by measuring A1AT levels. A1AT replacement is the only specific therapy for this condition. METHODS We describe the 1st patient with A1AT deficiency treated in this way in France. The patient was 52 years old at the start of treatment with A1AT replacement, initially in hospital and then at their place of residence. Treatment was initiated in the context of progressive breathlessness, the presence of emphysema and confirmation of the biochemical deficit. The patient received 4 g of AIAT per week in combination with inhaled corticosteroids and ongoing physical rehabilitation. Follow up over 20 years has revealed a slowing in the decline in spirometric measurements. No problems with tolerating the treatment have been reported. CONCLUSIONS In this clinical case replacement therapy appeared to show clinical benefits and was well tolerated.