Prenatal diagnosis of 3‐Hydroxy‐3‐methylglutaric aciduria by GC‐MS and enzymology on cultured amniocytes and chorionic villi

Abstract

, Middlesex. UK. 3-Hydrory-3-methylglutaric (HMO) aciduria is a disorder of L-leuc-ine metabolism and ketone body biosynthesis characteriaed by recurrent acute life-threatening episodes resembling Reye's syndrome. Prenatal diagnosis was requested by the parents of a child with this condition and was carried out by amniocenteeis at 16 weeks' gestation. Amniotic fluid concentrations (capillary GC and GC-HS) (Umole/L) were for W G 34.6 (N=1.21+0.38), 3-hydroryisovalerate (HIV) 33.9 (N=4.78f1.91). 3-methylglutaconate (3MAG) 31.7 (N=0.62-0.90) and 3-methylglutarate(3MG) 1.23 (N=0.12-0.26) consistent with an affected fetus. Termination was carried out on the basis of these data. The diagnosis was confirmed immediately by analysis of fetal plasma for organic acid6:concentra-tions of HMG, HIV, 3MAG and 3MG were 67.3, 36.9, 31.3 and 11.31lmoles/L respectively. Subsequent enzymology on cultured amoiocytes gave mean results for isovalerate incorporation into protein (pmol/h/mg protein) of 48 compared to simultaneous controls of 252; direct WIG CoA lyaS-3 activity (moles ilMG CoA removed/min/mg protein) was 0.05 compared to simultaneous controls of 9.16. Direct HMG CoA lyase measurements on chorionic villus tissue obtained at termination gave mean activities of 0.87 compared to controls of 8.04. These results provide the first prenatal diagnosis of HMG aciduria, demonstrate the rapid, accurate and unambiguous diagnosis at 16 weeks using direct GC-MS analysis of amniotic fluid and indicate the suitability of chorionic villus biopsy for future earlier (9 weeks) prenatal diagnoses of this condition. ORGANIC ACIDURIA IN PATIENTS WITH GLYCOGWOSIS TYPE I. Intrigued by the persistent growth retardation of some glucose-6-phosphatase-deficient patients, we investigated the urinary excretion of lactate, 2-oxoglutarate and citrate, reflecting organic acid overproduction , and glycerol reflecting impaired gluconeogenesis, in 17 patients with type I A and 1 patient with type IB glycogenosis. The urine was collected during 8-10 successive days twice daily. The mean lactate-creatinine ratio (mM/mM) ranged from 0.27 to 11.17 (normal 0.010 to0.058, N=36) in 5 patients with a height < P3. The lactate excretion in these patients varied considerably during successive days and less during gastric drip feeding at night. The mean lactate-creatinine ratio in the other patients was more constant and ranged from 0.04 to 0.34, The mean 2-oxoglutarate-creatinine ratio (mM/mM) ranged from 0.17 to 0.84 (normal 0 to 0.05, N=15) in 4 of 5 growth retarded patients. In the other patients it ranged from 0.01 to 0.43. The 2-oxoglutarate excretion per patient varied little. The mean citrate-creatinine ratio (mM/mM) ranged from 0.03 to 0.84 in all patients (normal 0.12 to 0.73, N=15). The mean glycerol-creatinine ratio (mM/mM) ranged from 0.01 to 0.11 (normal 0.005 to 0.03, n=15). We conclude that the lactate-creatinine ratio reflects both the adequacy of the dietary treatment and the severity of the disease, whereas the 2-oxoglutarate-creatinine ratio reflects...

Base molecular de la aciduria 3-hidroxi-3-metilglutárica

“…The confirmation of HL deficiency requires direct assay of the enzyme activity in leukocytes (47), fibroblasts (46) or liver biopsy (34,36). In prenatal diagnosis the pattern of organic acids in amniotic liquid (11) and in maternal urine between gestation week 23 and delivery have also been also used (14). HL activity has also been assayed in cultured amniocytes or chorionic villi (11,26,42).…”

“…In prenatal diagnosis the pattern of organic acids in amniotic liquid (11) and in maternal urine between gestation week 23 and delivery have also been also used (14). HL activity has also been assayed in cultured amniocytes or chorionic villi (11,26,42).…”