A significant association with asymptomatic joint hypermobility was observe
d in 37 children with a history of infantile hypertrophic pyloric stenosis
(P = .0016) and their parents (mothers, P < .0001; fathers, P < .05). The s
ubjects with articular hupermobility showed an increased frequency of absen
t mandibular frenulum, thereby suggesting the presence of a previously unre
cognized, systemic abnormality of the extracellular matrix.