Correction: A case of malignant hyperlactaemic acidosis appearing upon treatment with the mono-carboxylase transporter 1 inhibitor AZD3965.

Since the publication of this paper the authors noticed an error in the listed authors, where Alexandros Siskos was listed as Alexandros Sitkos. This has now been corrected.

A case of malignant hyperlactaemic acidosis appearing upon treatment with the mono-carboxylase transporter 1 inhibitor AZD3965.

A 47-year-old man with metastatic melanoma presented with refractory hyperlactaemic acidosis following the first dose of the mono-carboxylase transporter 1 inhibitor AZD3965 within a "first time in man" clinical trial. The mechanism of the agent and the temporal relationship suggested that this event was potentially drug related and recruitment was suspended. However, urinary metabolomics showed extensive abnormalities even prior to drug administration, leading to investigations for an underlying metabolic disorder. The lack of clinical symptoms from the elevated lactate and low blood glucose suggested a diagnosis of "hyper-Warburgism", where the high tumour burden was associated with extensive glucose uptake and lactate efflux from malignant cells, and the subsequent impact on blood biochemistry. This was supported by an FDG-PET scan showing extensive glucose uptake in numerous metastases and lack of uptake in the brain. A review of the literature showed 16 case reports of "hyper-Warburgism" in non-haematological malignancies, none of them with melanoma, with most associated with a poor outcome. The patient was treated symptomatically, but died 2 months later. The development of AZD3965 continues with the exclusion of patients with elevated plasma lactate at screening added to the protocol as a safety measure.Trial identification number ClinicalTrials.Gov. NCT01791595.

Cardiolipin fingerprinting of leukocytes by MALDI-TOF/MS as a screening tool for Barth syndrome.

Barth syndrome (BTHS), an X-linked disease associated with cardioskeletal myopathy, neutropenia, and organic aciduria, is characterized by abnormalities of card-iolipin (CL) species in mitochondria. Diagnosis of the disease is often compromised by lack of rapid and widely available diagnostic laboratory tests. The present study describes a new method for BTHS screening based on MALDI-TOF/MS analysis of leukocyte lipids. This generates a "CL fingerprint" and allows quick and simple assay of the relative levels of CL and monolysocardiolipin species in leukocyte total lipid profiles. To validate the method, we used vector algebra to analyze the difference in lipid composition between controls (24 healthy donors) and patients (8 boys affected by BTHS) in the high-mass phospholipid range. The method of lipid analysis described represents an important additional tool for the diagnosis of BTHS and potentially enables therapeutic monitoring of drug targets, which have been shown to ameliorate abnormal CL profiles in cells.

Barth syndrome without tetralinoleoyl cardiolipin deficiency: a possible ameliorated phenotype.

Barth syndrome (BTHS) is an X-linked disorder characterised by cardiac and skeletal myopathy, growth delay, neutropenia and 3-methylglutaconic aciduria (3-MGCA). Patients have TAZ gene mutations which affect metabolism of cardiolipin, resulting in low tetralinoleoyl cardiolipin (CL(4)), an increase in its precursor, monolysocardiolipin (MLCL), and an increased MLCL/CL(4) ratio. During development of a diagnostic service for BTHS, leukocyte CL(4) was measured in 156 controls and 34 patients with genetically confirmed BTHS. A sub-group of seven subjects from three unrelated families was identified with leukocyte CL(4) concentrations within the control range. This had led to initial false negative disease detection in two of these patients. MLCL/CL(4) in this subgroup was lower than in other BTHS patients but higher than controls, with no overlap between the groups. TAZ gene mutations in these families are all predicted to be pathological. This report describes the clinical histories of these seven individuals with an atypical phenotype: some features were typical of BTHS (five have had cardiomyopathy, one family has a history of male infant deaths, three have growth delay and five have 3-MGCA) but none has persistent neutropenia, five have excellent exercise tolerance and two adults are asymptomatic. This report also emphasises the importance of measurement of MLCL/CL(4) ratio rather than CL(4) alone in the biochemical diagnosis of the BTHS.

Acceptability of plasma ammonia results when samples are not transported and processed under ideal conditions.

BACKGROUND: It is recommended that samples for plasma ammonia analysis are kept chilled and processed promptly as in vitro metabolism causes falsely elevated results. Rejection of unsuitable samples can cause delayed diagnosis and treatment of hyperammonaemia with potentially serious clinical consequences. The Metabolic Biochemistry Network (MetBioNet) hyperammonaemia guideline recommends analysis of samples not collected under ideal conditions and reporting with appropriate comments. An audit found that some laboratories did not follow this guidance. An investigation was performed into whether storage at controlled room temperature and delayed sample processing affected interpretation of plasma ammonia results. METHODS: Eleven healthy volunteers provided informed consent. Blood was taken from each into 14 paediatric EDTA blood sample tubes, one placed immediately on ice, the others in a rack at room temperature. The chilled and baseline room temperature samples were centrifuged and plasma analysed by the Roche Ammonia (NH3L2) method. Samples stored at room temperature were analysed at 10-min intervals up to 2 h. RESULTS: Baseline room temperature ammonia was higher than in the chilled sample (19 ± 6.6 µmol/L [mean ± standard deviation] and 18 ± 6.6 µmol/L, respectively). Ammonia increased further by 0.09 ± 0.02 µmol/L per minute to 30 ± 8.4 µmol/L at 2 h. No result was above the reference range (50 µmol/L). No healthy subject with normal baseline ammonia would have been erroneously identified as having hyperammonaemia. CONCLUSIONS: Results support MetBioNet guidance that laboratories accept blood samples for ammonia analysis which are not processed under ideal conditions.

Diagnosis of Barth syndrome using a novel LC-MS/MS method for leukocyte cardiolipin analysis.

Barth syndrome (BTHS) is an X-linked disorder characterised by cardiomyopathy, skeletal myopathy, growth retardation, neutropenia and 3-methylglutaconic aciduria. It is caused by mutations in the TAZ gene which codes for tafazzin, a protein with acyl transferase activity involved in synthesis of cardiolipin. Monolysocardiolipin (MLCL) is an intermediate in this process. Diagnosis of BTHS is difficult, as clinical and biochemical features are variable and numerous TAZ mutations have been described. These factors, together with lack of a straightforward diagnostic test are thought to have contributed to under-diagnosis of the condition. A novel method for cardiolipin analysis by reversed-phase ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) is reported which is less complicated and faster than previously described methods and uses a readily available sample type. The equipment, reagents and expertise required are found in most clinical laboratories performing metabolic investigations. Leukocytes were prepared from whole blood, phospholipids extracted and tetralinoleyl cardiolipin (CL4) and MLCL analysed by UPLC-MS/MS. Reference values were derived from analysis of 76 control and 23 BTHS samples as follows: CL4 in controls >132 (95 % CI 100-169), BTHS <30.2 (21.3-40.4) pmol/mg protein; MLCL/CL4 ratio in controls <0.006 (0.004-0.009) and >2.52 (1.51-4.22) in BTHS patients. We describe an improved method for CL4 and MLCL/CL4 analysis which can be incorporated into the routine work of a clinical biochemistry laboratory. It shows 100 % sensitivity and specificity for BTHS, making it a suitable diagnostic test.

Broadening the Spectrum of SLC22A5 Phenotype: Primary Carnitine Deficiency Presenting with Focal Myoclonus.

Primary carnitine deficiency (PCD) is caused by pathogenic variants of the SLC22A5 gene, which encodes a transmembrane protein that functions as a high affinity carnitine transporter. Carnitine is essential for the transport of acyl-CoA, produced from fatty acids, into the mitochondria where they are oxidised to produce energy. We present the case history of an 8-year-old boy who presented with fever, lethargy, focal rhythmic (3 Hz) left wrist twitching, and severe encephalopathy. MRI brain showed basal ganglia involvement. Metabolic investigations revealed low serum carnitine; whole genome sequencing confirmed compound heterozygous SLC22A5 mutations. With carnitine replacement, intensive care support, and neurorehabilitation, he made a remarkable recovery, regaining independent breathing, speech, mobility, and hand use. Seizure presentation in PCD is rare and presentation with sustained focal myoclonus has not been previously reported. This case expands the known phenotype of PCD. Prompt carnitine replacement is imperative.

Incidental Detection of Classical Galactosemia through Newborn Screening for Phenylketonuria: A 10-Year Retrospective Audit to Determine the Efficacy of This Approach.

In the UK, Classical Galactosaemia (CG) is identified incidentally from the Newborn Screening (NBS) for phenylketonuria (PKU) using an "Other disorder suspected" (ODS) pathway when phenylalanine (Phe) and tyrosine (Tyr) concentrations are increased. We aimed to determine the efficacy of CG detection via NBS and estimate the incidence of CG in live births in the UK. A survey was sent to all UK NBS laboratories to collate CG cases diagnosed in the UK from 2010 to 2020. Cases of CG diagnosed were determined if detected clinically, NBS, or by family screening, as well as age at diagnosis. Cases referred via the ODS pathway were also collated, including the final diagnosis made. Responses were obtained from 13/16 laboratories. Between 2010 and 2020, a total of 6,642,787 babies were screened, and 172 cases of CG were identified. It should be noted that 85/172 presented clinically, 52/172 were identified by NBS, and 17/172 came from family screening. A total of 117 referrals were made via the ODS pathway, and 45/117 were subsequently diagnosed with CG. Median (interquartile range) age at diagnosis by NBS and clinically was 8 days (7-11) and 10 days (7-16), respectively (Mann-Whitney U test, U = 836.5, p-value = 0.082). The incidence of CG is 1:38,621 live births. The incidence of CG in the UK is comparable with that of other European/western countries. No statistical difference was seen in the timing of diagnosis between NBS and clinical presentation based on the current practice of sampling on day 5. Bringing forward the day of NBS sampling to day 3 would increase the proportion diagnosed with CG by NBS from 52/172 (30.2%) to 66/172 (38.4%).

Recurrent hyperammonaemia in a patient with carbonic anhydrase VA deficiency.

Carbonic anhydrase VA deficiency is a recently described inherited cause of paediatric hyperammonaemia. Most published cases describe patients with only one episode of hyperammonaemia whilst others report patients who had up to three metabolic crises with the first invariably being the most severe. We describe a patient with carbonic anhydrase VA deficiency who experienced 7 hyperammonemic episodes over a 3-year period, up to age 5 years 9 months. These episodes did not clearly decrease in severity over time. This report expands the clinical phenotype and the age window for metabolic crises associated with this condition.

The influence of genetic and environmental factors on plasma homocysteine concentrations in a population at high risk for coronary artery disease.

BACKGROUND: Elevated plasma total homocysteine (tHcy) predisposes to vascular disease and results from interactions between genetic and nutritional factors. MTHFR C(677)T increases tHcy in association with low folate. CBS 844ins68 lowers tHcy and negates the raising effect of MTHFR C(677)T in healthy subjects, but it is unclear if this is the case in subjects at high risk of vascular disease. This study examines the effect on plasma tHcy of interactions between these polymorphisms in an at-risk group. METHODS: Blood samples were collected from 376 subjects at increased risk of coronary artery disease. Plasma tHcy and vitamin B(6) were measured by HPLC and red cell folate and serum vitamin B(12) were measured by immuno-luminometric assay. MTHFR C(677)T and CBS 844ins68 status was established by standard PCR techniques. RESULTS: MTHFR TT predisposed to hyperhomocysteinaemia; this was increased in the presence of low folate (P<0.05) and vitamin B(12) (P<0.01). An inverse relationship was found between tHcy and folate (r=-0.42, P<0.0001), vitamin B(12) (r=-0.26, P<0.0005) and vitamin B(6) (r=-0.25, P<0.01). There was no interaction between plasma tHcy, vitamins or MTHFR C(677)T and CBS 844ins68. DISCUSSION: In this population at high risk of coronary artery disease, plasma tHcy was determined by vitamin status. This was exacerbated by the MTHFR C(677)T mutation. CBS 844ins68 did not influence tHcy and did not negate the tHcy-raising effect of MTHFR C(677)T.

Barth syndrome.

First described in 1983, Barth syndrome (BTHS) is widely regarded as a rare X-linked genetic disease characterised by cardiomyopathy (CM), skeletal myopathy, growth delay, neutropenia and increased urinary excretion of 3-methylglutaconic acid (3-MGCA). Fewer than 200 living males are known worldwide, but evidence is accumulating that the disorder is substantially under-diagnosed. Clinical features include variable combinations of the following wide spectrum: dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), endocardial fibroelastosis (EFE), left ventricular non-compaction (LVNC), ventricular arrhythmia, sudden cardiac death, prolonged QTc interval, delayed motor milestones, proximal myopathy, lethargy and fatigue, neutropenia (absent to severe; persistent, intermittent or perfectly cyclical), compensatory monocytosis, recurrent bacterial infection, hypoglycaemia, lactic acidosis, growth and pubertal delay, feeding problems, failure to thrive, episodic diarrhoea, characteristic facies, and X-linked family history. Historically regarded as a cardiac disease, BTHS is now considered a multi-system disorder which may be first seen by many different specialists or generalists. Phenotypic breadth and variability present a major challenge to the diagnostician: some children with BTHS have never been neutropenic, whereas others lack increased 3-MGCA and a minority has occult or absent CM. Furthermore, BTHS was first described in 2010 as an unrecognised cause of fetal death. Disabling mutations or deletions of the tafazzin (TAZ) gene, located at Xq28, cause the disorder by reducing remodeling of cardiolipin, a principal phospholipid of the inner mitochondrial membrane. A definitive biochemical test, based on detecting abnormal ratios of different cardiolipin species, was first described in 2008. Key areas of differential diagnosis include metabolic and viral cardiomyopathies, mitochondrial diseases, and many causes of neutropenia and recurrent male miscarriage and stillbirth. Cardiolipin testing and TAZ sequencing now provide relatively rapid diagnostic testing, both prospectively and retrospectively, from a range of fresh or stored tissues, blood or neonatal bloodspots. TAZ sequencing also allows female carrier detection and antenatal screening. Management of BTHS includes medical therapy of CM, cardiac transplantation (in 14% of patients), antibiotic prophylaxis and granulocyte colony-stimulating factor (G-CSF) therapy. Multidisciplinary teams/clinics are essential for minimising hospital attendances and allowing many more individuals with BTHS to live into adulthood.