Hydroxyproline is an imino acid normally present in human plasma. It is derived primarily from endogenous collagen turnover and the breakdown of dietary collagen. The finding of elevated (5- to 10-fold increase from the normal of less than ... Hydroxyproline is an imino acid normally present in human plasma. It is derived primarily from endogenous collagen turnover and the breakdown of dietary collagen. The finding of elevated (5- to 10-fold increase from the normal of less than 50 micromoles) serum hydroxyproline is thought to be an inherited defect in the catabolism of hydroxyproline.
Elevated serum hydroxyproline appears not to cause any significant clinical symptoms. Pelkonen and Kivirikko (1970) described hydroxyprolinemia in a brother and sister. No clinical abnormality was present and the authors suggested that hydroxyprolinemia, like cystathioninuria, is a 'non-disease.' ... Elevated serum hydroxyproline appears not to cause any significant clinical symptoms. Pelkonen and Kivirikko (1970) described hydroxyprolinemia in a brother and sister. No clinical abnormality was present and the authors suggested that hydroxyprolinemia, like cystathioninuria, is a 'non-disease.' Phang and Scriver (1989) stated that 'there is no evidence that the metabolic phenotype is a cause of clinical manifestation.' Bias of ascertainment is introduced by the fact that the hyperhydroxyprolinemia is found in patients investigated because of abnormality. They knew of reports of 6 probands. Kim et al. (1997) prospectively studied a girl with untreated hydroxyprolinemia identified on neonatal screening and compared her with her unaffected dizygotic twin sister. In the affected twin, plasma and urine hydroxyproline were increased 10-fold and 100-fold, respectively. Both girls had normal growth. On neuropsychologic testing, the affected twin was within normal limits, performing slightly better than her sister on verbal achievement but less well on visual perceptual testing. Kim et al. (1997) concluded that hydroxyprolinemia caused no physical or cognitive deficits. They could not rule out a possible effect on visual perceptual functioning.