Read more about this disease, some with Classification – Types – Signs and symptoms – Genetics – Pathophysiology – Diagnosis – Screening – Prevention – Treatment and management – Cures and much more, some including pictures and video when available.
Iminoglycinuria, sometimes called familial iminoglycinuria,[1][2][3] is an autosomal recessive[4] disorder of renal tubular transport affecting reabsorption of the amino acid glycine, and the imino acids proline and hydroxyproline.[4][5] This results in excess urinary excretion of all three acids (-uria denotes “in the urine”).[6]
Iminoglycinuria is a rare and complex disorder, associated with a number of genetic mutations which cause defects in both renal and intestinal transport systems of glycine and imino acids.[4][7][8][9]
Imino acids typically contain an imine functional group, instead of the amino group found in amino acids. Proline is considered and usually referred to as an amino acid,[10][11] but unlike others, it has a secondary amine. This feature, unique to proline, identifies proline also as an imino acid.[12] [13] Hydroxyproline is another imino acid, made from the naturally-occurring hydroxylation of proline.[12]
The primary characteristic of iminoglycinuria is the presence of glycine and imino acids in the urine. Otherwise, it is thought to be a relatively benign disorder,[14][6] although symptoms associated with disruptions of proline and glycine metabolism caused by malabsorption may be present with iminoglycinuria.[4][15] These include encephalopathy, mental retardation,[2] deafness,[3] blindness,[16] kidney stones,[17] hypertension[18] and gyrate atrophy.[19]
Gyrate atrophy is an inherited degenerative disorder of the retina and choroid,[20] sometimes accompanying the metabolic condition hyperornithinemia.[19][21] The presence of gyrate atrophy with iminoglycinuria stems from a deficiency of proline in chorioretinal tissues, while processes behind hyperornithinemia disrupt the metabolic pathway from ornithine to proline, which alters the catabolism of ornithine, and also results in reduced levels of proline. Thus, gyrate atrophy can be found with either disorder, with proline deficiency as an underlying feature.[22][19]
Hyperglycinuria is another disorder affecting reabsorption of glycine and imino acids, similar to iminoglycinuria and considered to be a heterozygous form.[3][4] When accompanied by a specific type of kidney stone (nephrolithiasis), it is sometimes referred to as “iminoglycinuria, type II”.[15][23][24]
Glycine, proline and hydroxyproline share common renal tubular mechanisms of reabsorption,[7] a function specific to the proximal tubule.[4][5] Both reabsorption or absorption of glycine and imino acids takes place respectively at the proximal tubule or intestinal brush border epithelium. The more selective transport of proline and other imino acids is driven at the molecular level by a mammalian cellular transport mechanism aptly known as system IMINO.[5][25][26]
[tubepress mode=’tag’, tagValue=’Iminoglycinuria’]