Hyaluronic acid (HA) is implicated in functions such as vascularity, morphogenesis, repair, and the general integrity of the extracellular matrix. Hence, it is considered possible that HA is involved in the most conspicuous features of the progeroid phenotype. However, it is not known whether the increase in HA excretion seen in progeria patients is due to a primary genetic defect or is a secondary effect due to some deeper problem. The phenomenon of 'normal' aging is suggested to have a more complex etiology and phenotype than progeria and the role of HA levels is less well-defined.