'Pseudohypertriglyceridemia' caused by hyperglycerolemia due to congenital enzyme deficiency

Delayed diagnosis of complex glycerol kinase deficiency in a Chinese male infant: a case report

BACKGROUND

Xp21 contiguous gene deletion syndrome is a rare genetic metabolic disorder with poor prognosis in infants, involving deletions of one or more genes in Xp21. When deletions of adrenal hypoplasia (AHC), Duchenne muscular dystrophy (DMD), and chronic granulomatosis (CGD) loci are included, complex glycerol kinase deficiency (CGKD) can be diagnosed. We present a case of CGKD that was initially misdiagnosed and died during treatment in our hospital in terms of improving our understanding of the clinical features and diagnosis of this disease, as well as highlighting the need for more precise dosing of corticosteroid replacement therapy.

CASE PRESENTATION

A 48-day-old full-term male infant was transferred to our medical center with global growth delay and persistent vomiting. Routine laboratory tests revealed hyperkalemia, hyponatremia, and a high level of creatine kinase. The initial diagnosis was adrenal cortical hyperplasia (ACH), then revised to adrenocortical insufficiency with a normal level of ACTH detected. After supplementing the routine lipid test and urinary glycerol test, CGKD was diagnosed clinically due to positive triglyceridemia and urinary glycerol, and the follow-up gene screening further confirmed the diagnosis. The boy kept thriving after corticosteroid replacement and salt supplementation. While levels of serum ACTH and cortisol decreased and remained low after corticosteroid replacement was administered. The patient died of acute type 2 respiratory failure and hypoglycemia after an acute upper respiratory tract infection, which may be the result of adrenal crisis after infection. Infants with CGKD have a poor prognosis, so physicians should administer regular follow-ups, and parents counseling during treatment to improve the survival of patients.

CONCLUSIONS

Overall, CGKD, although rare, cannot be easily excluded in children with persistent vomiting. Extensive blood tests can help to detect abnormal indicators. Adrenal crisis needs to be avoided as much as possible during corticosteroid replacement therapy.

Glycerol kinase deficiency in adults: Description of 4 novel cases, systematic review and development of a clinical diagnostic score

BACKGROUND AND AIMS

Glycerol kinase deficiency (GKD) is a rare genetic disorder characterized by hyperglycerolemia and glyceroluria, which could be misdiagnosed as a moderate to severe hypertriglyceridemia (HTG). We aimed to describe four novel cases of GKD, to complete a systematic review of all cases of isolated GKD published so far, and to develop a suspicion clinical diagnostic score for GKD.

METHODS

We reported four cases with suspicion of GKD and compared their phenotype with 584 males with triglycerides (TG) > 300 mg/dL, selected as control group (HTG non-GKD). The GK gene was sequenced in all cases. Lipoprotein particle concentrations were measured in all cases with GKD. The systematic review involved a PubMed, Cochrane and Scopus databases search to identify anthropometric and biochemical characteristics of all described cases with GKD.

RESULTS

The systematic review retrieved a total of 15 articles involving 39 subjects with GKD. GKD cases reported a history of high TG levels resistant to lipid-lowering therapy. Compared to GKD subjects (n = 43), HTG non-GKD subjects (n = 584) showed significantly higher BMI, total cholesterol, non-HDL cholesterol and gamma-glutamyltransferase, significantly lower HDL cholesterol and TG, and higher prevalence of diabetes. The proposed diagnostic score was significantly higher in GKD than in HTG non-GKD subjects.

CONCLUSIONS

This is the first systematic review that compiles all GKD cases reported to date including 4 novel cases, and examine the differential GKD phenotype compared to other types of HTG. The proposed score would have a broad utility in clinical practice to avoid unwarranted lipid lowering treatment in GKD patients.

The RNA-Binding Protein A1CF Regulates Hepatic Fructose and Glycerol Metabolism via Alternative RNA Splicing

The regulation of hepatic gene expression has been extensively studied at the transcriptional level; however, the control of metabolism through posttranscriptional gene regulation by RNA-binding proteins in physiological and disease states is less understood. Here, we report a major role for the hormone-sensitive RNA-binding protein (RBP) APOBEC1 complementation factor (A1CF) in the generation of hepatocyte-specific and alternatively spliced transcripts. Among these transcripts are isoforms for the dominant and high-affinity fructose-metabolizing ketohexokinase C and glycerol kinase, two key metabolic enzymes that are linked to hepatic gluconeogenesis and found to be markedly reduced upon hepatic ablation of A1cf. Consequently, mice lacking A1CF exhibit improved glucose tolerance and are protected from fructose-induced hyperglycemia, hepatic steatosis, and development of obesity. Our results identify a previously unreported function of A1CF as a regulator of alternative splicing of a subset of genes influencing hepatic glucose production through fructose and glycerol metabolism.

Primary Hypertriglyceridemia: A Look Back on the Clinical Classification and Genetics of the Disease

INTRODUCTION

Hypertriglyceridemia (HTG) is one of the most common metabolic disorders leading to pancreatitis and cardiovascular disease. HTG develops mostly due to impaired metabolism of triglyceride-rich lipoproteins. Although monogenic types of HTG exist, most reported cases are polygenic in nature.

AIM

This review article is focused on the classification of Primary HTG and the genetic factors behind its development with the aim of providing clinicians a useful tool for early detection of the disease in order to administer proper and effective treatment.

DISCUSSION

HTG is often characterized by a complex phenotype resulting from interactions between genetic and environmental factors. In many instances, the complexity, perplexing causes, and classification of HTG make it difficult for clinicians to properly diagnose and manage the disorder. Better availability of information on its pathophysiology, genetic factors involved, environmental causes, and their interactions could help in understanding such complex disorders and could support its effective diagnosis and treatment.

CONCLUSION

The current review has summarized the case definition, epidemiology, pathophysiology, clinical presentation, classification, associated genetic factors, and scope of genetic screening in the diagnosis of primary HTG.

Complex Glycerol Kinase Deficiency and Adrenocortical Insufficiency in Two Neonates

Contiguous gene deletions of chromosome Xp21 can lead to glycerol kinase deficiency and severe adrenocortical insufficiency (AI) in a male newborn among other problems. We describe our experience with two such patients who presented with dysmorphic facies, AI, and pseudo-hypertriglyceridemia. Both infants had normal serum 17-hidroxyprogesterone levels, and adrenal glands could not be observed with ultrasonography. Creatine kinase and triglyceride levels were measured to elucidate the etiology of adrenal hypoplasia and were above normal limits in both cases. Both patients required steroid and salt supplementation. They were both found to have Xp21.2 deletions (DMD, NR0B1, GK, IL1RAPL1). We conclude that AI in the context of other genetic abnormalities should prompt chromosomal investigations in the absence of another unifying explanation.

The polygenic nature of hypertriglyceridaemia: implications for definition, diagnosis, and management

Plasma triglyceride concentration is a biomarker for circulating triglyceride-rich lipoproteins and their metabolic remnants. Common mild-to-moderate hypertriglyceridaemia is typically multigenic, and results from the cumulative burden of common and rare variants in more than 30 genes, as quantified by genetic risk scores. Rare autosomal recessive monogenic hypertriglyceridaemia can result from large-effect mutations in six different genes. Hypertriglyceridaemia is exacerbated by non-genetic factors. On the basis of recent genetic data, we redefine the disorder into two states: severe (triglyceride concentration >10 mmol/L), which is more likely to have a monogenic cause; and mild-to-moderate (triglyceride concentration 2-10 mmol/L). Because of clustering of susceptibility alleles and secondary factors in families, biochemical screening and counselling for family members is essential, but routine genetic testing is not warranted. Treatment includes management of lifestyle and secondary factors, and pharmacotherapy. In severe hypertriglyceridaemia, intervention is indicated because of pancreatitis risk; in mild-to-moderate hypertriglyceridaemia, intervention can be indicated to prevent cardiovascular disease, dependent on triglyceride concentration, concomitant lipoprotein disturbances, and overall cardiovascular risk.

Transient pseudo-hypertriglyceridemia: a useful biochemical marker of fructose-1,6-bisphosphatase deficiency

Fructose-1,6-bisphosphatase (FBP) deficiency is an autosomal-recessive disorder of gluconeogenesis resulting from mutations within the FBP1 gene. During periods of trivial illness, individuals with FBP deficiency may develop ketotic hypoglycemia, metabolic acidosis, lactic acidemia, and an increased anion gap. Although detection of urinary excretion of glycerol by urine organic acid analysis has been previously described, the presence of transient pseudo-hypertriglyceridemia in serum during metabolic decompensation has not been reported before. This study describes four consanguineous Pakistani families, in which four patients were diagnosed with FBP deficiency. All showed transient pseudo-hypertriglyceridemia during the acute phase of metabolic decompensation, which resolved in a metabolically stable phase. Mutations in the FBP1 gene have been described from various ethnicities, but there is very limited literature available for the Pakistani population. This study also describes one novel mutation in the FBP1 gene which seems to be prevalent in Pakistani-Indian patients.

CONCLUSION

As a result of this study, transient pseudo-hypertriglyceridemia should be added to glyceroluria, ketotic hypoglycemia, metabolic acidosis, and lactic acidosis as a useful biochemical marker of FBP deficiency.

Isolated and contiguous glycerol kinase gene disorders: a review

Glycerol kinase deficiency (GKD) is an X-linked recessive disorder. There are two types. an isolated form and a complex form. We review the clinical, biochemical and molecular genetic features of GKD. The clinical and biochemical phenotype of isolated GKD may vary from a life-threatening childhood metabolic crisis to asymptomatic adult 'pseudohypertriglyceridaemia', resulting from hyperglycerolaemia. To date 38 patients from 24 families with isolated GKD have been reported. At least 7 of these patients had a metabolic crisis during a catabolic condition. The complex GKD is an Xp21 contiguous gene syndrome involving the glycerol kinase locus together with the adrenal hypoplasia congenita (AHC) or Duchenne muscular dystrophy (DMD) loci or both. Clinical features of a patient with complex GKD depend on the loci that are involved. Approximately 100 patients from 78 families with a complex GKD have been reported. Seventeen patients with complex GKD (AHC-GKD-DMD or AHC-GKD) died in the neonatal period or early childhood because of unrecognized or inappropriate management of adrenal dysfunction. Since the outcome of the crisis in GKD is highly dependent on the physicians' knowledge of the disease, we devised an algorithmic approach to the diagnosis. From molecular genetic investigations of isolated GKD, 7 missense mutations, 2 splice site mutations, I nonsense mutation, 1 Alu Sx insertion and 2 small deletions were reported for isolated GKD in 13 unrelated families. In 4 families consisting of more than one patient with the same biochemical and genetic defect, the phenotypic variability of the isolated GKD was remarkable. The clinical variability in isolated GKD cannot be explained by biochemical or by molecular heterogeneity. Isolated GKD patients showed a tendency towards hypoglycaemia with hyperketonaemia; whether the clinical symptoms of GKD are caused by dysfunction of gluconeogenesis and/or ketolysis needs to be investigated further.

AluY insertion (IVS4-52ins316alu) in the glycerol kinase gene from an individual with benign glycerol kinase deficiency

Glycerol kinase deficiency has three distinct forms: an isolated form which may be benign or symptomatic, and a complex form which is symptomatic and part of an Xp21 contiguous gene syndrome. Here we report the case of a male with benign isolated glycerol kinase deficiency who was incidentally identified after observation of pseudohypertriglyceridemia. DNA sequencing of this subject's glycerol kinase gene showed the insertion of an AluY sequence in intron 4 of the glycerol kinase gene. Although Alu insertions have been implicated in other diseases, and a closely related AluY element is found as an insert in the C1 inhibitor gene in patients with hereditary angioedema, this is the first case of glycerol kinase deficiency caused by an Alu insertion.

Isolated glycerol kinase deficiency in a neonate

Glycerol kinase deficiency occurs either as a relatively benign isolated enzyme deficiency, or as part of a syndrome resulting from a microdeletion in the p21 region of the X chromosome associated with congenital adrenal hypoplasia and/or Duchenne muscular dystrophy. Developmental delay is a consistent feature of the microdeletion syndrome but not of the isolated enzyme defect. We report a case of isolated glycerol kinase deficiency in a neonate presenting with hypotonia, apnea, mild developmental delay, and glyceroluria, without evidence of adrenal insufficiency or myopathy. A mild communicating hydrocephalus was noted on magnetic resonance imaging brain scan. It is important, therefore, to exclude glyceroluria in infants being investigated for apnea and hypotonia.

Congenital adrenal hypoplasia and glycerol kinase deficiency

An unusual case of salt-wasting in a male infant is reported. The cause was a small X-chromosomal deletion within Xp21 resulting in the syndrome of congenital adrenal hypoplasia with glycerol kinase deficiency. This syndrome can readily be diagnosed by routine biochemical tests.

Hypoglycemia: a pathophysiologic approach

An exploration of the factors that sustain glucose levels in the normal fasting subject reveals that the single major component is conservation of glucose rather than gluconeogenesis. Conservation is achieved by recycling of glucose carbon as lactate, pyruvate and alanine, and a profound decrease in the oxidation of glucose by the brain brought about by the provision and use of ketones. What glucose continues to be oxidized is for the most part formed from glycerol. Gluconeogenesis from protein plays little part in the process. Fasting hypoglycemia results from disorders affecting either one of the two critical sustaining factors--the recycling process or the availability and use of ketones. Individual hypoglycemic entities are examined against this background.

Deletion proximal to DXS68 locus (L1 probe site) in a boy with Duchenne muscular dystrophy, glycerol kinase deficiency, and adrenal hypoplasia

We report a case of a boy with Duchenne muscular dystrophy (DMD) associated with GK deficiency (GK), congenital adrenal hypoplasia (AHC), and mental retardation. Cytogenetic analysis of prometaphasic chromosomes revealed an interstitial chromosome deletion at Xp21.2 possibly extending to Xp21.1 or Xp21.3. His phenotypically normal mother was heterozygous for this deletion. DNA probe analysis on Southern blots showed that the deletion affected the following probe sites: 754, pERT 84, 21A, XJ2.3, pERT 87, JBir, and J66-H1, whereas L1, C7, and CX5.4 probes gave a normal signal. Pulse field gel electrophoresis after SfiI digestion did not show abnormal fragments with L1. These data are consistent with a deletion of about 4 megabases and indicate that the GK and AHC loci are proximal to L1 and distal to J66-H1.

Infantile glycerol kinase deficiency--a condition requiring prompt identification. Clinical, biochemical, and morphological findings in two cases

Infantile glycerol kinase deficiency (GKD) is an X-linked genetic disease characterized clinically by adrenal insufficiency and muscular dystrophy. The enzyme defect leads to increased levels of glycerol in blood and urine, which can be used for diagnosis. Without recognition of this condition, the chances for life-saving steroid treatment and for genetic counselling are missed. We report clinical, endocrinological, biochemical, and morphological findings in two non-related boys. One of them died in early infancy. The other is thriving at the age of 2 years although he is suffering from a myopathy not distinguishable from Duchenne muscular dystrophy. We discuss when to suspect and how to confirm the diagnosis of infantile GKD, and under what precautions the condition is detectable by commonly used screening procedures for inborn errors of metabolism.

Prenatal diagnosis of glycerol-kinase deficiency associated with a DNA deletion on the short arm of the X-chromosome

Amniocentesis was performed in a woman who previously had given birth to a boy who died at 12 months of age with a diagnosis of glyceroluria and adrenal insufficiency. A high amount of glycerol (9.0 standard deviations above mean for controls) was found in the amniotic fluid. Enzyme activity of glycerol-kinase (ATP:glycerol-3-phosphotransferase, EC 2.7.1.30) in the cultured amniotic fluid cells was very low. The pregnancy was terminated and a male fetus was aborted. Examinations of DNA isolated from the fetus did demonstrate deletions of two out of 16 DNA probes mapping to the short arm of the X-chromosome. The probes failing to hybridize to DNA from the fetus were C7 (DXS28) and L1.4 (DXS68), both mapping to Xp21.3 and located terminal to the Duchenne locus.

Deletion on the X chromosome detected by direct DNA analysis in one of two unrelated boys with glycerol kinase deficiency, adrenal hypoplasia, and Duchenne muscular dystrophy

In studies of the X chromosomes of two unrelated boys with adrenal hypoplasia, glycerol kinase deficiency, Duchenne muscular dystrophy, and mental retardation, conventional G banding did not reveal any numerical or structural abnormality, but direct DNA analysis with the X short-arm probes 754, C7, and OCT revealed a deletion in 1 of these patients. It is likely that both boys have a deletion at Xp21 affecting a number of closely linked disease-specific gene loci.

Duchenne muscular dystrophy, glycerol kinase deficiency, and adrenal insufficiency associated with Xp21 interstitial deletion

We report an interstitial deletion in the short arm of the X chromosome in a 6-year-old boy with Duchenne muscular dystrophy, glycerol kinase deficiency, adrenal insufficiency, intermittent hypoglycemia, spasticity, psychomotor retardation, and growth delay. His mother also has this deletion in an X chromosome. From our findings, we propose that the human glycerol kinase locus and the human X-linked adrenal hypoplasia locus are in the Xp21 band.

Liver glycerokinase deficiency in man with hyperglycerolaemia and hypertriglyceridaemia

Hyperglycerolaemia and glyceroluria is described in a patient who presented transient dietary-induced hypertriglyceridaemia. The increased glycerol in blood and urine was related to glycerokinase deficiency as evidenced by a hepatic tissue glycerokinase activity of one tenth (4.8 X 10(-5) mmol g-1 min-1) of that of normoglycerolaemic subjects (5.9 X 10(-4) ). As triglycerides are routinely determined by an enzymatic method after hydrolysis to glycerol, the differential diagnosis between true hypertriglyceridaemia and hyperglycerolaemia may prove difficult. Persisting "hypertriglyceridaemia' despite adequate dietary and drug treatment should suggest the existence of undiagnosed hyperglycerolaemia .

Human glycerol kinase deficiency: an inborn error of compartmental metabolism

Twelve individuals have been described with glycerol kinase deficiency. Five of these individuals are adults who were noted incidentally to have pseudohypertriglyceridemia. Six of these individuals are children who manifest a clinical complex which includes adrenal hypoplasia/insufficiency and developmental delay. Another child has intermittent coma, a normal IQ, and no evidence of adrenal insufficiency. Genetic and biochemical hypotheses are proposed to explain this clinical variability. Glycerol kinase binds specifically and reversibly to the porin, the pore-forming protein of the outer mitochondrial membrane, which also binds hexokinase. Mutations affecting any component of this kinase-binding system will alter the properties of this system. Glycerol kinase deficiency, as an inborn error of this compartmented metabolic system, offers an investigational opportunity for studying this microenvironment.