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At a glance

It is a benign inborn error of metabolism caused by a defect in renal tubular amino acid transport resulting in abnormal urinary excretion of glycine, proline, and hydroxyproline. The clinical manifestations include encephalopathy, mental retardation, deafness, blindness, renal lithiasis, mild to severe hypertension, and cerebral (gyrate) atrophy.

Synonym

Familial Iminoglycinuria.

Incidence

Homozygotes: 1:15,000 live births; heterozygotes: 2:100 in the general population.

Genetic inheritance

It is believed to be inherited as autosomal recessive. Heterozygotes may be “hyperglycinuric” (incomplete recessive), or silent (completely recessive).

Pathophysiology

Benign condition in which glycine and the imino acids proline and hydroxyproline have a decreased renal tubular reabsorption. Results from a specific inborn error of metabolism involving the common membrane carrier of these amino acids in the renal tubule.

Clinical aspects

Individuals with familial iminoglycinuria are asymptomatic. Excessive urinary proline, hydroxyproline, and glycine are normal findings in the first 6 months of life. In iminoglycinuria, urinary glycine excretion exceeds 150 mg in 24 hours, or endogenous renal clearance rate exceeds 8.6 mL/min/1.73 m2.

Anesthetic considerations

No specific precautions required for this condition.

References

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Bröer  S, Bailey  CG, Kowalczuk  S, Ng  C,  et al: Iminoglycinuria and hyperglycinuria are discrete human phenotypes resulting from complex mutations in proline and glycine transporters. J Clin Invest 118(12):3881–3892, 2008.  [PubMed: 19033659]
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Chesney  RW: Iminoglycinuria, in Scriver  CR, Beaudet  AL, Sly  WS, Valle  D (eds): The Metabolic and Molecular Bases of Inherited Disease, 7th ed. New York, McGraw-Hill, 1995, p 3643.

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