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Cystinuric heterozygotes and cystine-loading
Insights
Routine screening identified children with excessive dibasic amino acid excretion. Cystine loading tests helped distinguish normal individuals from cystinuric heterozygotes, classifying them into types II and III based on serum response.
Area of Science:
- Biochemistry
- Clinical Genetics
- Pediatric Medicine
Background:
- Amino acid disorders can manifest with psychiatric symptoms in children.
- Routine screening for amino acid disorders is crucial in pediatric populations.
- Dibasic aminoacidurias are a group of genetic disorders affecting amino acid transport.
Purpose of the Study:
- To investigate the prevalence of excessive dibasic amino acid excretion in children presenting with psychiatric conditions.
- To characterize cystinuric heterozygotes identified during routine screening.
- To differentiate between types of cystinuric heterozygotes using a cystine loading test.
Main Methods:
- Thin layer chromatography was used for routine screening of amino acid disorders.
- A cystine loading test was administered to probands, their families, and controls.
- Urinary amino acid excretion and serum response were analyzed post-loading.
Main Results:
- Six children with excessive dibasic amino acid excretion were detected during routine screening.
- Cystine loading differentiated normal subjects from cystinuric heterozygotes.
- Cystinuric heterozygotes were further subclassified into type II and type III based on serum response.
Conclusions:
- Routine screening can identify individuals with excessive dibasic amino acid excretion.
- Cystine loading tests are effective in characterizing cystinuric heterozygotes.
- The study provides a method for subtyping cystinuric heterozygotes, aiding in genetic counseling and management.
Abstract:
During routine screening procedures for amino acid disorders by thin layer chromatography, performed in a children's psychiatric hospital, we detected 6 children who excreted excessive amounts of dibasic amino acids. The probands, their siblings and parents and 11 controls (29 subjects in all) were loaded with cystine. On the basis of the urinary excretion after the loading we distinguished normal subjects from cystinuric heterozygotes, which we further subdivided in heterozygotes type II and III by the corresponding serum response.