An unusual case of alpha-1-antitrypsin deficiency: SZ/Z

A female patient was first seen at age 65 due to a diagnosis of alpha-1-antitrypsin deficiency (AATD). She was a lifelong non-smoker, with no significant history of second hand smoke exposure. There was no prior family history of AATD or liver disease. Her serum AAT concentration was measured on two occasions and in both cases, concentration was <0.21 g/L. The patient was referred for genetic testing to determine her SERPINA1 (the gene responsible for AATD) genotype. Three deficiency alleles were identified: she was heterozygous for S, a mild deficiency allele, and homozygous for Z, a severe deficiency allele. This case represents unusual convergence of three pathogenic SERPINA1 variants in a single individual. We report the investigations used to clarify her unusual genotype and propose non-crossover gene conversion as the likely mechanism.