Alpha 1 antitrypsin deficiency alleles are associated with joint dislocation and scoliosis in Williams syndrome

Elastin haploinsufficiency is responsible for a significant portion of the Williams syndrome (WS) phenotype including hoarse voice, supravalvar aortic stenosis (SVAS), hernias, diverticuli of bowel and bladder, soft skin, and joint abnormalities. All of the connective tissue signs and symptoms are variable in the WS population, but few factors other than age and gender are known to influence the phenotype. We examined a cohort of 205 individuals with WS for mutations in SERPINA1, the gene that encodes alpha-1-antitrypsin (AAT), the inhibitor of elastase. Individuals with classic WS deletions and SERPINA1 genotypes PiMS or PiMZ were more likely than those with a SERPINA1 PiMM genotype to have joint dislocation or scoliosis. However, carrier status for AAT deficiency was not correlated with presence of inguinal hernia or with presence or severity of SVAS. These findings suggest that genes important in elastin metabolism are candidates for variability in the connective tissue abnormalities in WS.