Notably, SERPINA1, causal gene for α1-antitrypsin deficiency if mutated [46], is expressed in epithelial (club, mucin-producing and ciliated cells) and antigen-presenting cells, suggesting that multiple cell types may contribute to the pathogenesis of α1-antitrypsin deficiency. This evidence concerns the gene SERPINA1 and hyperinsulinemic hypoglycemia, familial, 4.