Our study investigated alpha 1 antitrypsin deficiency (AATD) diagnosis in a family originated from central Tunisia and showing a familial history of asthma. Biochemical and genetic diagnosis for AATD was performed according to current diagnostic standards. AAT level quantification in affected individuals showed plasma AAT levels consistent with intermediate AATD (ranged from 0.91 to 1.04 g/L). The molecular analysis was assessed using the genotyping of the most prevalent PI*S and PI*Z SERPINA1 mutations and the sequencing of AAT coding exons for rare AATD variants detection. No PI*S or PI*Z deficient variants were seen in this family. Sequencing results showed the inheritance of the deficient rare variant PI*M(wurzburg) (P369S) at the heterozygous state in the mother and two affected siblings. However, AATD status remains unexplained in the third affected case, with no mutations detected in the AAT coding exons.