UX007 for the treatment of long chain-fatty acid oxidation disorders: Safety and efficacy in children and adults following 24weeks of treatment.

BACKGROUND: Long-chain fatty acid oxidation disorders (LC-FAOD) lead to accumulation of high concentrations of potentially toxic fatty acid intermediates. Newborn screening and early intervention have reduced mortality, but most patients continue to experience frequent hospitalizations and significant morbidity despite treatment. The deficient energy state can cause serious liver, muscle, and heart disease, and may be associated with an increased risk of sudden death. Triheptanoin is a medium odd-chain fatty acid. Anaplerotic metabolites of triheptanoin have the potential to replace deficient tricarboxylic acid (TCA) cycle intermediates, resulting in net glucose production as a novel energy source for the treatment of LC-FAOD. STUDY DESIGN: A single-arm, open-label, multicenter Phase 2 safety and efficacy study evaluated patients with severe LC-FAOD evidenced by ongoing related musculoskeletal, cardiac, and/or hepatic events despite treatment. After a four-week run-in on current regimen, investigational triheptanoin (UX007) was titrated to a target dose of 25-35% of total daily caloric intake. Patients were evaluated on several age/condition-eligible endpoints, including submaximal exercise tests to assess muscle function/endurance (12-minute walk test; 12MWT) and exercise tolerance (cycle ergometry), and health related quality of life (HR-QoL). Results through 24weeks of treatment are presented; total study duration is 78weeks. RESULTS: Twenty-nine patients (0.8 to 58years) were enrolled; most qualified based on severe musculoskeletal disease. Twenty-five patients (86%) completed the 24-week treatment period. At Week 18, eligible patients (n=8) demonstrated a 28% increase (LS mean=+181.9 meters; p=0.087) from baseline (673.4meters) in 12MWT distance. At Week 24, eligible patients (n=7) showed a 60% increase in watts generated (LS mean=+409.3W; p=0.149) over baseline (744.6W) for the exercise tolerance test. Improvements in exercise tests were supported by significant improvements from baseline in the adult (n=5) self-reported SF-12v2 physical component summary score (LS mean=+8.9; p<0.001). No difference from baseline was seen in pediatric parent-reported (n=5) scores (SF-10) at Week 24. Eighteen patients (62%) had treatment-related adverse events, predominantly gastrointestinal (55%), mild-to-moderate in severity, similar to that seen with prior treatment with medium chain triglyceride (MCT) oil. One patient experienced a treatment-related serious adverse event of gastroenteritis. One patient discontinued from study due to diarrhea of moderate severity; the majority of patients (25/29; 86%) elected to continue treatment in the extension period. CONCLUSIONS: In patients with severe LC-FAOD, UX007 interim study results demonstrated improved exercise endurance and tolerance, and were associated with positive changes in self-reported HR-QoL.

DNA methylation in the pathophysiology of hyperphenylalaninemia in the PAH(enu2) mouse model of phenylketonuria.

Phenylalanine hydroxylase deficient phenylketonuria (PKU) is the paradigm for a treatable inborn error of metabolism where maintaining plasma phenylalanine (Phe) in the therapeutic range relates to improved clinical outcomes. While Phe is the presumed intoxicating analyte causal in neurologic damage, the mechanism(s) of Phe toxicity has remained elusive. Altered DNA methylation is a recognized response associated with exposure to numerous small molecule toxic agents. Paralleling this effect, we hypothesized that chronic Phe over-exposure in the brain would lead to aberrant DNA methylation with secondary influence upon gene regulation that would ultimately contribute to PKU neuropathology. The PAH(enu2) mouse models human PKU with intrinsic hyperphenylalaninemia, abnormal response to Phe challenge, and neurologic deficit. To examine this hypothesis, we assessed DNA methylation patterns in brain tissues using methylated DNA immunoprecipitation and paired end sequencing in adult PAH(enu2) animals maintained under either continuous dietary Phe restriction or chronic hyperphenylalaninemia. Heterozygous PAH(enu2/WT) litter mates served as controls for normal Phe exposure. Extensive repatterning of DNA methylation was observed in brain tissue of hyperphenylalaninemic animals while Phe restricted animals displayed an attenuated pattern of aberrant DNA methylation. Affected gene coding regions displayed aberrant hypermethylation and hypomethylation. Gene body methylation of noncoding RNA genes was observed and among these microRNA genes were prominent. Of particular note, observed only in hyperphenylalaninemic animals, was hypomethylation of miRNA genes within the imprinted Dlk1-Dio3 locus on chromosome 12. Aberrant methylation of microRNA genes influenced their expression which has secondary effects upon the expression of targeted protein coding genes. Differential hypermethylation of gene promoters was exclusive to hyperphenylalaninemic PAH(enu2) animals. Genes with synaptic involvement were targets of promoter hypermethylation that resulted in down-regulation of their expression. Gene dysregulation secondary to abnormal DNA methylation may be contributing to PKU neuropathology. These results suggest drugs that prevent or correct aberrant DNA methylation may offer a novel therapeutic option to management of neurological symptoms in PKU patients.

Triheptanoin treatment in patients with pediatric cardiomyopathy associated with long chain-fatty acid oxidation disorders.

Long-chain fatty acid oxidation disorders (LC-FAOD) can cause cardiac hypertrophy and cardiomyopathy, often presenting in infancy, typically leading to death or heart transplant despite ongoing treatment. Previous data on triheptanoin treatment of cardiomyopathy in LC-FAOD suggested a clinical benefit on heart function during acute failure. An additional series of LC-FAOD patients with critical emergencies associated with cardiomyopathy was treated with triheptanoin under emergency treatment or compassionate use protocols. Case reports from 10 patients (8 infants) with moderate or severe cardiomyopathy associated with LC-FAOD are summarized. The majority of these patients were detected by newborn screening, with follow up confirmatory testing, including mutation analysis; all patients were managed with standard treatment, including medium chain triglyceride (MCT) oil. While on this regimen, they presented with acute heart failure requiring hospitalization and cardiac support (ventilation, ECMO, vasopressors) and, in some cases, resuscitation. The patients discontinued MCT oil and began treatment with triheptanoin, an investigational drug. Triheptanoin is expected to provide anaplerotic metabolites, to replace deficient TCA cycle intermediates and improve effective energy metabolism. Cardiac function was measured by echocardiography and ejection fraction (EF) was assessed. EF was moderately to severely impaired prior to triheptanoin treatment, ranging from 12-45%. Improvements in EF began between 2 and 21days following initiation of triheptanoin, and peaked at 33-71%, with 9 of 10 patients achieving EF in the normal range. Continued treatment was associated with longer-term stabilization of clinical signs of cardiomyopathy. The most common adverse event observed was gastrointestinal distress. Of the 10 patients, 7 have continued on treatment, 1 elected to discontinue due to tolerability issues, and 2 patients died from other causes. Two of the case histories illustrate that cardiomyopathy may also develop later in childhood and/or persist into adulthood. Overall, the presented cases suggest a therapeutic effect of triheptanoin in the management of acute cardiomyopathy associated with LC-FAOD.

Urinary phenylacetylglutamine as dosing biomarker for patients with urea cycle disorders.

UNLABELLED: We have analyzed pharmacokinetic data for glycerol phenylbutyrate (also GT4P or HPN-100) and sodium phenylbutyrate with respect to possible dosing biomarkers in patients with urea cycle disorders (UCD). STUDY DESIGN: These analyses are based on over 3000 urine and plasma data points from 54 adult and 11 pediatric UCD patients (ages 6-17) who participated in three clinical studies comparing ammonia control and pharmacokinetics during steady state treatment with glycerol phenylbutyrate or sodium phenylbutyrate. All patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate or sodium phenylbutyrate in a cross over fashion and underwent 24-hour blood samples and urine sampling for phenylbutyric acid, phenylacetic acid and phenylacetylglutamine. RESULTS: Patients received phenylbutyric acid equivalent doses of glycerol phenylbutyrate ranging from 1.5 to 31.8 g/day and of sodium phenylbutyrate ranging from 1.3 to 31.7 g/day. Plasma metabolite levels varied widely, with average fluctuation indices ranging from 1979% to 5690% for phenylbutyric acid, 843% to 3931% for phenylacetic acid, and 881% to 1434% for phenylacetylglutamine. Mean percent recovery of phenylbutyric acid as urinary phenylacetylglutamine was 66.4 and 69.0 for pediatric patients and 68.7 and 71.4 for adult patients on glycerol phenylbutyrate and sodium phenylbutyrate, respectively. The correlation with dose was strongest for urinary phenylacetylglutamine excretion, either as morning spot urine (r = 0.730, p < 0.001) or as total 24-hour excretion (r = 0.791 p<0.001), followed by plasma phenylacetylglutamine AUC(24-hour), plasma phenylacetic acid AUC(24-hour) and phenylbutyric acid AUC(24-hour). Plasma phenylacetic acid levels in adult and pediatric patients did not show a consistent relationship with either urinary phenylacetylglutamine or ammonia control. CONCLUSION: The findings are collectively consistent with substantial yet variable pre-systemic (1st pass) conversion of phenylbutyric acid to phenylacetic acid and/or phenylacetylglutamine. The variability of blood metabolite levels during the day, their weaker correlation with dose, the need for multiple blood samples to capture trough and peak, and the inconsistency between phenylacetic acid and urinary phenylacetylglutamine as a marker of waste nitrogen scavenging limit the utility of plasma levels for therapeutic monitoring. By contrast, 24-hour urinary phenylacetylglutamine and morning spot urine phenylacetylglutamine correlate strongly with dose and appear to be clinically useful non-invasive biomarkers for compliance and therapeutic monitoring.

Cognitive and adaptive functioning after liver transplantation for maple syrup urine disease: a case series.

MSUD is a complex metabolic disorder that has been associated with central nervous system damage, developmental delays, and neurocognitive deficits. Although liver transplantation provides a metabolic cure for MSUD, changes in cognitive and adaptive functioning following transplantation have not been investigated. In this report, we present data from 14 patients who completed cognitive and adaptive functioning testing pre- and one yr and/or three yr post-liver transplantation. Findings show either no significant change (n=8) or improvement (n=5) in IQ scores pre- to post-liver transplantation. Greater variability was observed in adaptive functioning scores, but the majority of patients evidenced no significant change (n=8) in adaptive scores. In general, findings indicate that liver transplantation minimizes the likelihood of additional central nervous system damage, providing an opportunity for possible stabilization or improvement in neurocognitive functioning.

Molecular basis of dimethylglycine dehydrogenase deficiency associated with pathogenic variant H109R.

Dimethylglycine dehydrogenase (DMGDH) is a mitochondrial matrix flavoprotein that catalyses the demethylation of dimethylglycine to form sarcosine, accompanied by the reduction of the covalently bound FAD cofactor. Electron-transfer flavoprotein reoxidizes the reduced flavin and transfers reducing equivalents to the main mitochondrial respiratory chain through the enzyme ETF-ubiquinone oxidoreductase. DMGDH plays a prominent role in choline and 1-carbon metabolism. We have expressed the mature form of human DMGDH and the H109R variant identified in a DMGDH-deficient patient as N-terminally His(6)-tagged proteins in E. coli. The enzymes were purified to homogeneity by nickel affinity and anion exchange chromatography. The presence of FAD in the wild-type enzyme was confirmed by spectrophotometric analysis. The H109R variant, however, had only 47% of the wild-type level of bound flavin as expressed in E. coli, indicating its reduced affinity for FAD As previously described for rat enzyme studies, the wild-type human enzyme exhibited two K (m) values for N,N-dimethylglycine (K (m1) = 0.039 +/- 0.010 mmol/L and K(m2) = 15.4 +/- 1.2 mmol/L). The addition of 4 micromol/L tetrahydrofolate resulted in a slight decrease in specific activity and a substantial decrease in K (m2) (1.10 +/- 0.55 mmol/L). The flavinated H109R variant protein exhibited a 27-fold decrease in specific activity and a 65-fold increase in K (m), explaining its pathogenicity. Additionally, the current expression system represents a significant improvement over a previously described rat DMGDH expression system and will enhance our ability to further study this important metabolic enzyme.

Essential fatty acid profiling for routine nutritional assessment unmasks adrenoleukodystrophy in an infant with isovaleric acidaemia.

We report a 16-month-old asymptomatic male with enzyme confirmed isovaleric acidaemia (IVA; isovaleryl-CoA dehydrogenase deficiency; OMIM 243500) who, upon routine nutritional follow-up, presented evidence of peroxisomal dysfunction. The newborn screen (2 days of life) revealed elevated C(5)-carnitine (2.95 µmol/L; cutoff <0.09 µmol/L) and IVA was subsequently confirmed by metabolic profiling and in vitro enzymology. Plasma essential fatty acid (EFA) analysis, assessed to evaluate nutritional status during protein restriction and L: -carnitine supplementation, revealed elevated C(26:0) (5.0 µmol/L; normal <1.3). Subsequently, metabolic profiling and molecular genetic analysis confirmed X-linked adrenoleukodystrophy (XALD). Identification of co-inherited XALD with IVA in this currently asymptomatic patient holds significant treatment ramifications for the proband prior to the onset of neurological sequelae, and critically important counselling implications for this family.

Precision medicine in the age of big data: The present and future role of large-scale unbiased sequencing in drug discovery and development.

High throughput molecular and functional profiling of patients is a key driver of precision medicine. DNA and RNA characterization has been enabled at unprecedented cost and scale through rapid, disruptive progress in sequencing technology, but challenges persist in data management and interpretation. We analyze the state-of-the-art of large-scale unbiased sequencing in drug discovery and development, including technology, application, ethical, regulatory, policy and commercial considerations, and discuss issues of LUS implementation in clinical and regulatory practice.

Identification of the catalytic residue of human short/branched chain acyl-CoA dehydrogenase by in vitro mutagenesis.

The acyl-CoA dehydrogenases (ACDs) are a family of related enzymes which catalyze the alpha,beta-dehydrogenation of acyl-CoA esters, transferring electrons to electron transferring flavoprotein. We have recently cloned and characterized the cDNA for human short/branched chain acyl-CoA dehydrogenase (SBCAD). Based on homology with the other ACDs we hypothesized that E381 is the catalytic residue for this enzyme. Alteration of this amino acid to glutamine, glycine or arginine resulted in an inactive enzyme. Substitution of aspartate at this position led to an enzyme with reduced activity compared to the wild type. An E381G/G260E double mutation (which places a glutamate in a position homologous to the catalytic residue identified in other members of this gene family) restored enzyme activity. These data confirm the crucial nature of E381 to the activity of this enzyme and strongly support its role as the alpha-proton abstracting base.

Long-chain acyl-CoA dehydrogenase is a key enzyme in the mitochondrial beta-oxidation of unsaturated fatty acids.

The first reaction of mitochondrial beta-oxidation, which is catalyzed by acyl-CoA dehydrogenases, was studied with unsaturated fatty acids that have a double bond either at the 4,5 or 5,6 position. The CoA thioesters of docosahexaenoic acid, arachidonic acid, 4,7,10-cis-hexadecatrienoic acid, 5-cis-tetradecenoic acid, and 4-cis-decenoic acid were effectively dehydrogenated by both rat and human long-chain acyl-CoA dehydrogenases (LCAD), whereas they were poor substrates of very long-chain acyl-CoA dehydrogenases (VLCAD). VLCAD, however, was active with CoA derivatives of long-chain saturated fatty acids or unsaturated fatty acids that have double bonds further removed from the thioester function. Although bovine LCAD effectively dehydrogenated 5-cis-tetradecenoyl-CoA (14:1) and 4,7,10-cis-hexadecatrienoyl-CoA, it was nearly inactive toward the other unsaturated substrates. The catalytic efficiency of rat VLCAD with 14:1 as substrate was only 4% of the efficiency determined with tetradecanoyl-CoA, whereas LCAD acted equally well on both substrates. The conclusion of this study is that LCAD serves an important, if not essential function in the beta-oxidation of unsaturated fatty acids.

Human long chain, very long chain and medium chain acyl-CoA dehydrogenases are specific for the S-enantiomer of 2- methylpentadecanoyl-CoA.

The acyl-CoA dehydrogenases are a family of mitochondrial flavoenzymes involved in fatty acid and branched chain amino-acid metabolism. Long chain acyl-CoA dehydrogenase (LCAD) and short/branched chain acyl-CoA dehydrogenase (SBCAD) have been shown to have activity towards 2-methyl branched chain acyl-CoA substrates of varying chain lengths. In humans, long chain 2-branched chain fatty acids such as pristanic acid are largely thought to be metabolized in peroxisomes through desaturation of their CoA esters by branched chain acyl-CoA oxidase, but LCAD is also capable of utilizing 2-methyldecanoyl- and 2-methylpalmitoyl-CoA as substrate [1]. Since the acyl-CoA oxidase reaction is specific for the S-enantiomer of the branched chain substrates, we investigated the stereo specificity of mitochondrial LCAD. Purified LCAD had a specific activity of 390 and 340 mU/mg of purified LCAD protein using palmitoyl-CoA and S-2-methylpentadecanoyl-CoA, respectively, as substrate. No activity was measurable with R-2-methylpentadecanoyl-CoA. Purified medium chain acyl-CoA dehydrogenase (MCAD) could also utilize S-2-methylpentadecanoyl-CoA as a substrate, but not R-2-methylpentadecanoyl-CoA. These results indicate that LCAD and MCAD are specific for the S-enantiomers of methylbranched chain substrates. Crude mitochondrial extracts showed no activity when dehydrogenating activity was measured with R/S-2-methylpalmitoyl-CoA or S-2-methylpentadecanoyl-CoA after inactivation of the extract with antibodies to very long chain acyl-CoA dehydrogenase and MCAD, suggesting that this substrate is not useful in identifyig clinical deficiencies of LCAD.

High-level expression of an altered cDNA encoding human isovaleryl-CoA dehydrogenase in Escherichia coli.

Isovaleryl-CoA dehydrogenase (IVD) catalyzes the conversion of isovaleryl-CoA to 3-methylcrotonyl-CoA in the leucine catabolism pathway. The cDNA encoding the mature human IVD polypeptide was cloned in a prokaryotic expression vector, but the level of expression in Escherichia coli was extremely low and attempts to purify the enzyme to homogeneity were unsuccessful. To enhance expression, the nucleotide sequence of 22 codons within the 111-bp region at the 5'-end of the cDNA was altered to accommodate E. coli codon usage without altering the amino-acid coding sequence. The altered IVD cDNA was synthesized by PCR, using a primer containing the desired modifications. Following overnight induction of the E. coli transformed with this cDNA, the enzyme was purified to homogeneity using diethylaminoethyl agarose and high-pressure ceramic hydroxyapatite resins. IVD activity was increased 165-fold in the crude extract of cells containing the modified cDNA, as compared to that containing the wild-type cDNA.

Cloning of genomic and cDNA for mouse isovaleryl-CoA dehydrogenase (IVD) and evolutionary comparison to other known IVDs.

Isovaleryl-CoA dehydrogenase (IVD) is an intramitochondrial homotetrameric flavoenzyme that catalyzes the conversion of isovaleryl-CoA to 3-methylcrotonyl-CoA in the leucine catabolism pathway. Deficiency of IVD in humans causes isovaleric acidemia, which shows tremendous clinical variability for reasons that are unknown. To help better understand this disorder, we have cloned and sequenced the mouse IVD genomic and cDNAs. The mouse IVD gene spans approximately 17 kb and contains 12 coding exons organized identically to the human gene. It maps to mouse chromosome 2 in the area of band 2E4-E5, corresponding to the syntenic region of human chromosome 15. Mouse IVD predicted amino acid sequences are 95.8 and 89.6% identical to that of the rat and human sequences, respectively, with conservation of key functional residues. We have now identified IVD sequences from seven species. Comparison of these sequences shows that the rat and mouse proteins are the most closely related, both of which, in turn, share highest homology to human. All of the mammalian enzymes appear to be more closely related than any of the IVDs on other branches of the phylogram, while the fly and worm IVDs are the most divergent. The invertebrate IVDs are more closely related to the mammalian enzymes than to those from two plant species.

Short-chain acyl-CoA dehydrogenase deficiency: a cause of ophthalmoplegia and multicore myopathy.

OBJECTIVE: To determine an underlying genetic defect within the differential diagnosis of congenital multicore myopathy. BACKGROUND: A 13.5-year-old girl presented with congenital-onset facial and neck weakness, slowly progressive severe limb girdle and axial myopathy, respiratory weakness, cardiomyopathy, progressive joint contractures, lumbar lordosis, progressive external ophthalmoplegia with ptosis, and cataracts. Muscle biopsy at 3 years revealed type I fiber predominance and hypotrophy, multicores with a focal decrease in mitochondria and oxidative enzymes, and internal nuclei. METHODS AND RESULTS: Serum carnitine was decreased (total, 18.2 micromol/L; free, 11.7 micromol/L). Urine organic acids intermittently revealed very large amounts of ethylmalonic and methylsuccinic acids intermittently, with elevated butyrylglycine, 2-methylbutyrylglycine, and tiglylglycine. Fibroblast acylcarnitine profiles revealed marked butyrylcarnitine elevation. Electron-transferring flavoprotein-linked reduction enzymatic assay of fibroblasts with butyryl-coenzyme A (CoA) as substrate, after immunoinactivation of medium-chain acyl-CoA dehydrogenase activity, revealed a complete absence of short-chain acyl-CoA dehydrogenase (SCAD) activity. No SCAD protein was detectable with Western blot analysis. CONCLUSIONS: This patient expands the clinical phenotype of SCAD deficiency and emphasizes the need for its consideration in the differential diagnosis of progressive external ophthalmoplegia and congenital multicore myopathy.

Heritable connective tissue disorders in cervical artery dissections: a prospective study.

We prospectively evaluated 15 consecutive patients with spontaneous cervical artery dissections. Three patients (20%) had a heritable connective tissue disorder, each with a unique phenotype. None of these patients met the criteria of any of the named syndromes, and collagen and fibrillin analyses were normal. Heritable connective tissue disorders are common among patients with spontaneous cervical artery dissections, but, despite intensive investigations, the type of disorder usually cannot be identified. The underlying arteriopathy in cervical artery dissections is likely to be heterogeneous.

Purification of monoclonal antibodies to human alkaline phosphatases by antigen-immunoaffinity chromatography: comparisons of their molar binding values.

Antigen-immunoaffinity chromatography has been used to purify monoclonal antibodies to human alkaline phosphatases. The binding of the purified antibodies to various alkaline phosphatases was tested utilizing an electrophoretic titration assay. The results indicate that binding differences among the various ALPs seen with several of the antibodies are due to antigenic differences in the molecular structure of the enzymes. We define a molar binding value as the minimum molar concentration of antibody necessary to complex all of the ALP in a standard reaction mixture. These values varied widely, indicating marked differences in the avidities of the different antibodies.

pUC18rspL: a plasmid vector for indirect selection and direct sequencing of promoter-bearing DNA fragments.

Plasmid pUC18rspL is a 3.788-kilobase pair vector, derived from pUC18, pKK232-8 and pHSG664, which identifies promoter-bearing DNA fragments functional in StrA E. coli by activation of a promoterless streptomycin-sensitive gene cartridge (rspL). Expression of the plasmid-borne rspL gene leads to sensitivity dominance and death of the cell. Promoter-bearing DNA fragments can be cloned within a synthetic polylinker containing 12 unique restriction nuclease target sequences. After transformation of StrA E. coli TB1, ampicillin-resistant transformants are replica plated on medium containing ampicillin and streptomycin to identify promoters cloned in their functional orientation. These elements can be sequenced without additional subcloning steps from the M13 universal forward primer hybridization site located 5' of the polylinker in the pUC18 contribution. Transcriptional terminators are cloned 3' of the rspL gene to maintain a balance between transcription and replication when high signal strength promoters such as the E. coli Tac promoter are analyzed. pUC18rspL is used to clone transcriptional promoters from the extreme thermophile T. aquaticus. Promoter signal strength can be estimated by determining the extent of sensitivity dominance conferred to the host.

The changing face of disorders of fatty acid oxidation.

OBJECTIVE: To review the current understanding of the rapidly changing field of disorders of fatty acid metabolism and to discuss the future directions for research. DESIGN: A literature review of the basic biochemistry of the beta-oxidation pathway and clinical cases of defects of fatty acid metabolism are presented, and the diagnosis and treatment of such defects are discussed. MATERIAL AND METHODS: In many cases, a correct diagnosis will be made only if these disorders are specifically considered and appropriate tests are obtained, because results of screening tests for other organic acidemias are often normal in these entities. RESULTS: The first disorder of fatty acid metabolism was described only 20 years ago. Since then, at least 15 different inborn errors of metabolism that affect beta-oxidation have been identified, most in the past 10 years. Within the past 5 years, investigators have realized that a deficiency of one of these enzymes, medium-chain acyl coenzyme A dehydrogenase, may be one of the most common inborn errors of metabolism. This disorder may have a frequency equal to that of phenylketonuria in some populations in the United States and northern Europe. Approximately 1 to 3% of all unexplained deaths during infancy and childhood are probably related to disorders of beta-oxidation. Diagnosis of these disorders can be difficult because of the intermittent nature of the excretion of characteristic compounds. The mainstay of therapy for defects of beta-oxidation is avoidance of fasting. CONCLUSION: All patients with a suspected defect of fatty acid metabolism should be assessed and monitored by a specialist trained in the care of such patients. Continued improvements in the ability to diagnose and treat these disorders will be directly linked to new advances in the basic research on these enzymes. Movements to screen newborns for medium-chain acyl coenzyme A dehydrogenase are under way in some medical centers. Proposed tests include metabolite analysis or direct mutation analysis (or both) from blood spots from newborn screening cards already obtained for every newborn in the United States.

Hepatic lymphangiomatosis mimicking polycystic liver disease.

Hepatic lymphangiomatosis is a rare disorder characterized by cystic dilatation of the lymphatic vessels in the hepatic parenchyma. It can occur in the liver alone, in the liver and spleen, or in multiple organs. Clinically, diagnosis can be difficult because of the rarity and protean manifestations of this disorder. We describe a 53-year-old woman with hepatic lymphangiomatosis in whom polycystic liver disease had been previously diagnosed. In addition, we review 12 cases of hepatic, splenic, and hepatosplenic lymphangiomatosis with or without systemic lymphangiomatosis and discuss the differential diagnosis.

Sandrow syndrome of mirror hands and feet and facial abnormalities.

In 1970, Sandrow et al. (J Bone Joint Surg 52-A:363-370) described a syndrome of ulnar and fibular dimelia with facial abnormalities present in 2 generations in a family. We describe a new patient with similar manifestations, establishing this constellation of anomalies as a distinct syndrome.