Rhabdomyolysis as a presenting manifestation of very long-chain acyl-coenzyme a dehydrogenase deficiency

Biochemical and molecular characteristics among infants with abnormal newborn screen for very-long-chain acyl-CoA dehydrogenase deficiency: A single center experience

Objective

To define the biochemical and molecular characteristics and diagnostic outcomes of a large US cohort of VLCAD deficiency positive cases as detected by newborn screening (NBS) with MS:MS. This relatively common disorder of fatty acid oxidation is screened for in every state in America and often results in extensive testing of multiple samples to arrive at a diagnostic conclusion.

Materials and methods

We compared NBS dried blood spot (DBS) acylcarnitine profile (ACP) C14, C14:1, C14:2, C14:1/C12:1 ratio and plasma C14, C14:1, C14:2, C14:1/C12:1, C14:1/C16 and C14:1/C2 ratios among true positive and false positive cases. Results of VLCAD enzyme analysis, molecular testing and fibroblast fatty acid oxidation probe assay were analyzed.

Results

The presence of compound heterozygous or homozygous pathogenic variants, along with elevations of C14, C14:1 and C14:1/C12:1 ratio, identified 19 VLCAD deficiency cases. All were asymptomatic at most recent follow-up visits. The C14:1/C12:1 ratio in NBS-DBS ACP and plasma acylcarnitine profiles at follow-up (follow-up plasma ACP), is the most useful marker to differentiate between true and false positive cases. Among all cases with molecular analysis data available, approximately 56.7% had a single pathogenic mutation. Lymphocyte enzyme analysis (n = 61) was uninformative in 23% of cases studied.

Conclusion

VLCAD deficiency NBS by MS:MS is highly effective at identifying asymptomatic affected infants. Our cohort showed that elevation of C14:1/C12:1, in both NBS DBS and plasma ACP, was informative in discriminating affected from unaffected individuals and contributes to improve the accuracy of confirmatory testing of infants with presumptive positive for VLCAD deficiency.

Recognizing and Managing a Metabolic Crisis

In some relatively common inborn errors of metabolism there can be the accumulation of toxic compounds including ammonia and organic acids such as lactate and ketoacids, as well as energy deficits at the cellular level. The clinical presentation is often referred to as a metabolic emergency or crisis. Fasting and illness can result in encephalopathy within hours, and without appropriate recognition and intervention, the outcome may be permanent disability or death. This review outlines easy and readily available means of recognizing and diagnosing a metabolic emergency as well as general guidelines for management. Disease-specific interventions focus on parenteral nutrition to reverse catabolism, toxin removal strategies, and vitamin/nutrition supplementation.

Pervasive inflammatory activation in patients with deficiency in very-long-chain acyl-coA dehydrogenase (VLCADD)

OBJECTIVES

Very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is a disorder of fatty acid oxidation. Symptoms are managed by dietary supplementation with medium-chain fatty acids that bypass the metabolic block. However, patients remain vulnerable to hospitalisations because of rhabdomyolysis, suggesting pathologic processes other than energy deficit. Since rhabdomyolysis is a self-destructive process that can signal inflammatory/immune cascades, we tested the hypothesis that inflammation is a physiologic dimension of VLCADD.

METHODS

All subjects (n = 18) underwent informed consent/assent. Plasma cytokine and cytometry analyses were performed. A prospective case analysis was carried out on a patient with recurrent hospitalisation. Health data were extracted from patient medical records.

RESULTS

Patients showed systemic upregulation of nine inflammatory mediators during symptomatic and asymptomatic periods. There was also overall abundance of immune cells with high intracellular expression of IFNγ, IL-6, MIP-1β (CCL4) and TNFα, and the transcription factors p65-NFκB and STAT1 linked to inflammatory pathways. A case analysis of a patient exhibited already elevated plasma cytokine levels during diagnosis in early infancy, evolving into sustained high systemic levels during recurrent rhabdomyolysis-related hospitalisations. There were corresponding activated leukocytes, with higher intracellular stores of inflammatory molecules in monocytes compared to T cells. Exposure of monocytes to long-chain free fatty acids recapitulated the cytokine signature of patients.

CONCLUSION

Pervasive plasma cytokine upregulation and pre-activated immune cells indicate chronic inflammatory state in VLCADD. Thus, there is rationale for practical implementation of clinical assessment of inflammation and/or translational testing, or adoption, of anti-inflammatory intervention(s) for personalised disease management.

Clinical manifestations and management of fatty acid oxidation disorders

Fatty acid oxidation disorders (FAOD) are a group of rare, autosomal recessive, metabolic disorders caused by variants of the genes for the enzymes and proteins involved in the transport and metabolism of fatty acids in the mitochondria. Those affected by FAOD are unable to convert fatty acids into tricarboxylic acid cycle intermediates such as acetyl-coenzyme A, resulting in decreased adenosine triphosphate and glucose for use as energy in a variety of high-energy-requiring organ systems. Signs and symptoms may manifest in infants but often also appear in adolescents or adults during times of increased metabolic demand, such as fasting, physiologic stress, and prolonged exercise. Patients with FAOD present with a highly heterogeneous clinical spectrum. The most common clinical presentations include hypoketotic hypoglycemia, liver dysfunction, cardiomyopathy, rhabdomyolysis, and skeletal myopathy, as well as peripheral neuropathy and retinopathy in some subtypes. Despite efforts to detect FAOD through newborn screening and manage patients early, symptom onset can be sudden and serious, even resulting in death. Therefore, it is critical to identify quickly and accurately the key signs and symptoms of patients with FAOD to manage metabolic decompensations and prevent serious comorbidities.

Very-Long-Chain Acyl-Co-Enzyme A Dehydrogenase Deficiency Presenting as Rhabdomyolysis: First Case Report from Sri Lanka

Background

Rhabdomyolysis can be either inherited or acquired such as in metabolic myopathies. Very-long-chain acyl-CoA dehydrogenase deficiency is a rare fatty acid oxidation disorder which presents with different phenotypes, and the mild adult form can present as intermittent rhabdomyolysis. Here, we present the first adult case of very-long-chain acyl-CoA dehydrogenase deficiency presenting as rhabdomyolysis in a Sri Lankan patient. Case Presentation. A 36-year-old Sri Lankan man who was born to consanguineous parents presented with severe generalized muscle pain, stiffness, and dark-coloured urine for three days following prolonged low-intensity activity. Since fourteen years of age, he has had multiple similar episodes, where one episode was complicated with acute kidney injury. His eldest brother also suffered from the similar episode. Examination revealed only generalized muscle tenderness without any weakness. His creatine phosphokinase level was above 50,000 IU/L, and he had myoglobinuria. Molecular genetic tests confirmed the diagnosis of very-long-chain acyl-CoA dehydrogenase deficiency. Following a successful recovery devoid of complications, he remained asymptomatic with lifestyle adjustments.

Conclusion

Very-long-chain acyl-CoA dehydrogenase deficiency is a rare inherited cause of metabolic myopathy that gives rise to intermittent rhabdomyolysis in adults. Prompt diagnosis is essential to prevent complications and prevent its recurrence.

Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. Online, open access of the full published guideline allows utilization by health care providers, researchers and collaborators who advise, advocate and care for individuals with VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Investigating the genetic susceptibility to exertional heat illness

Background

We aimed to identify rare (minor allele frequency ≤1%), potentially pathogenic non-synonymous variants in a well-characterised cohort with a clinical history of exertional heat illness (EHI) or exertional rhabdomyolysis (ER). The genetic link between malignant hyperthermia (MH) and EHI was investigated due to their phenotypic overlap.

Methods

The coding regions of 38 genes relating to skeletal muscle calcium homeostasis or exercise intolerance were sequenced in 64 patients (mostly military personnel) with a history of EHI, or ER and who were phenotyped using skeletal muscle in vitro contracture tests. We assessed the pathogenicity of variants using prevalence data, in silico analysis, phenotype and segregation evidence and by review of the literature.

Results

We found 51 non-polymorphic, potentially pathogenic variants in 20 genes in 38 patients. Our data indicate that RYR1 p.T3711M (previously shown to be likely pathogenic for MH susceptibility) and RYR1 p.I3253T are likely pathogenic for EHI. PYGM p.A193S was found in 3 patients with EHI, which is significantly greater than the control prevalence (p=0.000025). We report the second case of EHI in which a missense variant at CACNA1S p.R498 has been found. Combinations of rare variants in the same or different genes are implicated in EHI.

Conclusion

We confirm a role of RYR1 in the heritability of EHI as well as ER but highlight the likely genetic heterogeneity of these complex conditions. We propose defects, or combinations of defects, in skeletal muscle calcium homeostasis, oxidative metabolism and membrane excitability are associated with EHI.

Bi-allelic mutations in TRAPPC2L result in a neurodevelopmental disorder and have an impact on RAB11 in fibroblasts

Background

The combination of febrile illness-induced encephalopathy and rhabdomyolysis has thus far only been described in disorders that affect cellular energy status. In the absence of specific metabolic abnormalities, diagnosis can be challenging.

Objective

The objective of this study was to identify and characterise pathogenic variants in two individuals from unrelated families, both of whom presented clinically with a similar phenotype that included neurodevelopmental delay, febrile illness-induced encephalopathy and episodes of rhabdomyolysis, followed by developmental arrest, epilepsy and tetraplegia.

Methods

Whole exome sequencing was used to identify pathogenic variants in the two individuals. Biochemical and cell biological analyses were performed on fibroblasts from these individuals and a yeast two-hybrid analysis was used to assess protein-protein interactions.

Results

Probands shared a homozygous TRAPPC2L variant (c.109G>T) resulting in a p.Asp37Tyr missense variant. TRAPPC2L is a component of transport protein particle (TRAPP), a group of multisubunit complexes that function in membrane traffic and autophagy. Studies in patient fibroblasts as well as in a yeast system showed that the p.Asp37Tyr protein was present but not functional and resulted in specific membrane trafficking delays. The human missense mutation and the analogous mutation in the yeast homologue Tca17 ablated the interaction between TRAPPC2L and TRAPPC10/Trs130, a component of the TRAPP II complex. Since TRAPP II activates the GTPase RAB11, we examined the activation state of this protein and found increased levels of the active RAB, correlating with changes in its cellular morphology.

Conclusions

Our study implicates a RAB11 pathway in the aetiology of the TRAPPC2L disorder and has implications for other TRAPP-related disorders with similar phenotypes.

Metabolomic study of corticosterone-induced cytotoxicity in PC12 cells by ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

Glucocorticoids (GCs) have been proved to be an important pathogenic factor of some neuropsychiatric disorders. Usually, a classical injury model based on corticosterone-induced cytotoxicity of differentiated rat pheochromocytoma (PC12) cells was used to stimulate the state of GC damage of hippocampal neurons and investigate its potential mechanisms involved. However, up to now, the mechanism of corticosterone-induced cytotoxicity in PC12 cells was still looking forward to further elucidation. In this work, the metabolomic study of the biochemical changes caused by corticosterone-induced cytotoxicity in differentiated PC12 cells with different corticosterone concentrations was performed for the first time, using the ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF MS). Partial least squares-discriminate analysis (PLS-DA) indicated that metabolic profiles of different corticosterone treatment groups deviated from the control group. A total of fifteen metabolites were characterized as potential biomarkers involved in corticosterone-induced cytotoxicity, which were corresponding to the dysfunctions of five pathways including glycerophospholipid metabolism, sphingolipid metabolism, oxidation of fatty acids, glycerolipid metabolism and sterol lipid metabolism. This study indicated that the rapid and holistic cell metabolomics approach might be a powerful tool to further study the pathogenesis mechanism of corticosterone-induced cytotoxicity in PC12 cells.