Dimethylglycine dehydrogenase deficiency | Fish odor syndrome, myopathy | Accumulation of dimethylglycine | AR, DMGDH gene on 5q12.2-q12.3 | Analysis of betaine and DMG in plasma, mutation testing | No specific treatment available |
Sarcosinemia (sarcosine dehydrogenase deficiency) | No consistent phenotype | Accumulation of sarcosine | AR, SDH gene on 9q34 | Analysis of plasma amino acids | No specific treatment available |
Glycine N-methyltransferase | Mild hepatomegaly, transaminasemia | Isolated accumulation of methionine and SAM | AR, GNMT gene on 6p12 | Analysis of plasma amino acids, tHcy, and SAM | No specific treatment available |
Phosphoserine phosphatase deficiency | Retardation of growth and psychomotor development, facial
dysmorphism | Defective biosynthesis of serine, leading to serine deficiency | AR, PSPH gene on 7q15.2-q15.1 | Analysis of plasma and CSF amino acids, enzyme assay, mutation
testing | Serine supplementation |
Hyperprolinemia type 1 (proline dehydrogenase deficiency) | Inconstant association with cognitive impairment, epilepsy,
psychiatric symptoms | Defective proline catabolism leads to accumulation of proline | AR, PRODH gene on 22q11.2, often microdeletions | Analysis of amino acids in plasma or urine, mutation analysis | No specific treatment available |
Hyperprolinemia type 2 (delta-1-pyrroline-5-carboxylate
dehydrogenase deficiency) | Epilepsy, mental retardation | Defect in catabolism of proline leads to accumulation of
proline and its precursors | AR, P5CDH gene on 1p36 | Analysis of amino acids and pyrroline-5-carboxylate in plasma
or urine, enzyme assay, mutation testing | No specific treatment available |
Delta-1-pyrroline-5-carboxylate synthetase deficiency | Neurodegeneration, cataracts, connective tissue laxity | Insufficient synthesis of proline and ornithine with secondary
disruption of the urea cycle | AR, PCS gene on 10q24.3 | Amino acids, ammonia, mutation analysis | Supplementation of L-proline andL-ornithine |