There are three disease tyes affecting proine metabolism. 1. Affecting catabolism of proline (e.g. hyperprolinemia type I and type II); 2. Affecting synthesis of proline (e.g. P5CS- and P5CR-deficiencies); 3. Accumulation of proline-containing peptides (e.g. prolidase deficiency).
This pathway was inspired by Chapter 5 (edition 4) of the book of Blau (ISBN 3642403360 (978-3642403361)), Fig. 5.4.