An 8.5-year-old girl with classical maple syrup urine disease (MSUD) required liver transplantation for hypervitaminosis A and was effectively cured of MSUD over an 8-year clinical follow-up period. We developed a collaborative multidisciplinary effort to evaluate the effects of elective liver transplantation in 10 additional children (age range 1.9-20.5 years) with classical MSUD. Patients were transplanted with whole cadaveric livers under a protocol designed to optimize safe pre-and post-transplant management of MSUD. All patients are alive and well with normal allograft function after 106 months of follow-up in the index patient and a median follow-up period of 14 months (range 4-18 months) in the 10 remaining patients. Leucine, isoleucine and valine levels stabilized within 6 hours post-transplant and remained so on an unrestricted protein intake in all patients. Metabolic cure was documented as a sustained increase in weight-adjusted leucine tolerance, normalization of plasma concentration relationships among branched-chain and other essential and nonessential amino acids, and metabolic and clinical stability during protein loading and intercurrent illnesses. Costs and risks associated with surgery and immune suppression were similar to other pediatric liver transplant populations.

The pathophysiology of pre-eclampsia is contested, but one hypothesis indicates that it is a heterogeneous condition in which only a subset of affected women bear smallfor-gestational age (SGA) babies. In intrauterine growthrestricted (IUGR) infants, placental transport of amino acids is diminished and the resulting decrease in cordblood amino acid concentrations is thought to contribute to their stunted growth. In contrast, the metabolic syndrome (dyslipidaemia, hyperinsulinaemia, hyperglycaemia, hypertension and obesity) which is associated with high amino acid concentrations is more prevalent in women with pre-eclampsia. The focus of this study was to compare maternal and fetal serum amino acid concentrations during normal pregnancy and pre-eclampsia and to evaluate the associations between the amino acid concentrations and fetal growth. The results indicate that maternal and cord-blood amino acid concentrations were significantly higher in women with pre-eclampsia compared with normal pregnant women and the concentrations were inversely associated with measures of infant growth. Maternal and cord-blood amino acid concentrations were also significantly higher in pre-eclamptic mothers with SGA infants compared with pre-eclamptic mothers whose babies were not SGA. These data indicate that, in contrast to IUGR, pre-eclampsia is associated with enhanced placental amino acid transport or reduced fetal amino acid utilization. Furthermore, the data are consistent with the hypothesis that pre-eclampsia is a heterogeneous disease associated with the metabolic syndrome.

We report 2 patients with isolated 3-methylcrotonyl-coenzyme A carboxylase deficiency whose urine was devoid of, or contained only trace, 3-methylcrotonylglycine, the pathognomonic marker for this disorder. The first patient, a girl with trisomy 21, was detected through newborn screening with an elevated 5 carbon hydroxycarnitine species level, and the second patient came to clinical attention at the age of 5 months because of failure to thrive and developmental delay. Investigation of urinary organic acids revealed an elevated 3-hydroxyisovaleric acid level but no demonstrable 3-methylcrotonylglycine in both patients. Enzyme studies in cultured fibroblasts confirmed isolated 3-methylcrotonyl-coenzyme A carboxylase deficiency with residual activities of 5% to 7% and 12% of the median control value, respectively. Incorporation of 14C-isovaleric acid into intact fibroblasts was essentially normal, showing that the overall pathway was at least partially functional and potentially explaining the absence of 3-methylcrotonylglycine in urine. Mutation analysis of the MCCA and MCCB genes revealed that both patients were compound heterozygous for a missense mutation, MCCB-c.1015G-->A (p.V339M), and a second mutation that leads to undetectable MCCB messenger (poly A+) RNA. Absent or trace 3-methylcrotonylglycine levels in urine raises the potential for misdiagnosis in the clinical biochemical genetics laboratory based solely on urine organic acid analysis using combined gas chromatography-mass spectrometry.

Context.—Whether cell membrane fatty acid (FA) composition is a useful indicator of vascular disease is unclear. Objective.—To study variation of erythrocyte (RBC) membrane FA in samples from healthy volunteers, hospitalized patients, and cardiac troponin I–elevated patients with myocardial damage without a priori assumptions as to FA composition. Design.—We separated FAs extracted from RBCs by gas chromatography and identified them by mass spectrometry. Fatty acids with abundance greater than 1% of total were quantified and compared: hexadecanoic (C16:0), octadecadienoic (C18:2), cis- and trans-octadecenoic (C18:1), and eicosatetraenoic (C20:4) acids. Deuterated standards established proportionality of FA recovery. The cis- and trans-C18:1 identification was verified by comparison with standards. Results.—In troponin-positive samples, C18:2 to C18:1 ratios were increased 30% compared with healthy controls or with random patient samples. Erythrocyte trans-C18:1 had a wide variation, ∼10-fold, in all groups but without differences between groups. Replicates showed that the wide range of RBC trans-FA load is not due to analytic variation. In healthy subjects, the RBC content of lower– molecular weight FAs (C16-C18) correlated with serum low-density lipoprotein cholesterol, but despite the established relationship between dietary trans-FA and increased low-density lipoprotein cholesterol, lipid profiles had no correlation with RBC trans-FA content. Conclusions.—Erythrocyte accumulation of unsaturated FA may be a useful indicator of vascular disease, whereas the wide range in trans-FAs suggests that both diet and genetic variation affect RBC trans-FA accumulation. Unsaturated FAs increase membrane fluidity and may reflect a natural response to subclinical vascular changes, which may in turn reflect increased risk of clinical disease.