Prolidase deficiency is a rare disorder inherited through an autosomal recessive gene. The hallmark of the disorder are iminodipeptiduria, chronic skin ulcers, recurring infections, mental retardation and characteristic facial appearance, although prolidase deficiency can occur with no clinical manifestation. The primary biological function of the enzyme involves the metabolism of collagen degradation products and the recycling of proline for collagen resynthesis. We describe two patients with prolidase deficiency and review the different clinical manifestations suggesting the pathogenetic mechanism through few hypotheses.