PEPD and connective tissue disorder: It is a severe autosomal recessive connective tissue disorder linked to mutations in the prolidase gene (PEPD,19cen-q13.11), which encodes for prolidase (peptidase D, EC 3.4.13.9), the only human enzyme catalyzing the hydrolysis of dipeptides containing proline or hydroxyproline residues at their C-terminal end.