Buss et al. (2007) identified a heterozygous 1254G-T transversion in the SERPINA6 gene, resulting in the D367N substitution, in a 22-year-old Swiss male patient with severe muscle fatigue, usually after stressful events. Extensive biochemical and endocrine analysis showed decreased serum CBG and increased serum cortisol in response to ACTH or catecholamine administration. Investigation of other family members showed that the mutation occurred de novo on the paternal allele. Buss et al. (2007) proposed that SERPINA6 deficiency may act as an autosomal dominant disorder with incomplete penetrance, although a second pathogenic mutation could not be excluded.