Iminoglycinuria is believed to be inherited in an autosomal recessive manner. This means a defective gene responsible for the disorder is located on an autosome, and inheritance requires two copies of the defective gene—one from each parent. Parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.

A non-inherited cause of excess urinary excretion of proline and glycine, similar to that found in iminoglycinuria, is quite common to newborn infants younger than 6 months. Sometimes referred to as neonatal iminoglycinuria, it is due to underdevelopment of high-affinity transport mechanisms within the renal circuit, specifically PAT2, SIT1 and SLC6A18. The condition corrects itself with age. In cases where this persists beyond childhood, however, inherited hyperglycinuria or iminoglycinuria may be suspected.

Iminoglycinuria, sometimes called familial iminoglycinuria, is an autosomal recessive disorder of renal tubular transport affecting reabsorption of the amino acid glycine, and the imino acids proline and hydroxyproline. This results in excess urinary excretion of all three acids ("-uria" denotes "in the urine").

Iminoglycinuria is a rare and complex disorder, associated with a number of genetic mutations that cause defects in both renal and intestinal transport systems of glycine and imino acids.

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, but unlike others, it has a secondary amine. This feature, unique to proline, identifies proline also as an imino acid. Hydroxyproline is another imino acid, made from the naturally occurring hydroxylation of proline.

Inborn errors of renal tubular transport are metabolic disorders which lead to impairment in the ability of solutes, such as salts or amino acids, to be transported across the brush border of the renal tubule. This results in disruptions of renal reabsorption.

Examples of these disorders include Iminoglycinuria, renal tubular acidosis and Gitelman syndrome.