Identification of potential interferents of methylmalonic acid: A previously unrecognized pitfall in clinical diagnostics and newborn screening.

OBJECTIVES: Determination of methylmalonic acid (MMA) from dried blood spots (DBS) is commonly performed in clinical diagnostics and newborn screening for propionic acidemia (PA) and methylmalonic acidemia. Isobaric compounds of MMA having the same mass can affect diagnostic reliability and quantitative results, which represents a previously unrecognized pitfall in clinical assays for MMA. We set out to identify interfering substances of MMA in DBS, serum and urine samples from confirmed patients with PA and methylmalonic acidemia. METHODS: Techniques included quadrupole time-of-flight high-resolution mass spectrometry (QTOF HR-MS), nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography (LC) and tandem mass spectrometry (MS/MS). RESULTS: The five isobaric metabolites detected in DBS, serum and urine from PA and methylmalonic acidemia patients were confirmed as 2-methyl-3-hydroxybutyrate, 3-hydroxyisovalerate, 2-hydroxyisovalerate, 3-hydroxyvalerate and succinate using a series of experiments. An additional unknown substance with low abundance remained unidentified. CONCLUSIONS: The presented results facilitate the diagnostic and quantitative reliability of the MMA determination in clinical assays. Isobaric species should be investigated in assays for MMA to eliminate possible interference in a wide range of conditions including PA, methylmalonic acidemia, a vitamin B12 deficiency, ketosis and lactic acidosis.

A retrospective analysis of metabolic control in children with PKU in the COVID-19 era.

Background: Patients with phenylketonuria (PKU) must maintain a lifelong natural protein-restricted diet to prevent neuro-cognitive damage. Early diagnosis is established with newborn screening, with diet subsequently controlled by regular phenylalanine (Phe) monitoring. During the COVID-19 pandemic, significant lockdown measures were introduced that may have influenced the above. Aim of our study: To establish whether the diagnosis was delayed in neonates during the pandemic. In addition, metabolic control was further assessed during the COVID-19 pandemic era (CE) compared to the same period a year prior (non-COVID-19 era, NCE). The lockdown periods (LD) were also compared with unrestricted periods (URP). Patients methods: Six neonates born during the CE and eight neonates born during NCE were included in the newborn screening analysis. Seventy-two classical PKU patients aged 2-18 years and categorized as children (2-12 years; 51 patients) and adolescents (>13 years; 21 patients) were included in the metabolic control analysis. The frequency of dried blood spot (DBS) sampling and Phe levels were assessed according to the different periods. Results: There was no diagnostic or therapeutic delay in reaching the recommended Phe range in neonates born during CE compared to those born in NCE (median [interquartile range, IQR]: 23.5 [22.5-24] vs. 22 [18.0-27] days, p = NS). The cumulative DBS sampling frequency in children increased by 9.9% in the CE while no change was noted in the adolescent group. The median Phe level increased significantly in both age groups in the CE, but remained within the recommended target range. During CE, changes in Phe levels differed in the two age groups: children had the highest median Phe in the second lockdown period (LD2), while the adolescents had an increased Phe in URP.There were significant negative correlations between DBS sampling frequencies and Phe levels in both age groups in NCE (children: r - 0.43, p = 0.002; adolescents r = -0.37, p = 0.012), and in adolescents in CE (r = -0.62, p = 0.006). Conclusion: The pandemic did not impact newborn metabolic screening. The increased frequency of DBS sampling in CE and good target Phe levels suggest a better compliance in a very sensitive period. Since many factors may impact metabolic control in the different age groups, further studies are needed to analyse their respective role.

Quality of life in children living with PKU - a single-center, cross-sectional, observational study from Hungary.

BACKGROUND: Phenylketonuria (PKU) is an inherited error of metabolism, screened at 48-72 h of life since 1975 in Hungary. The patients have to keep a strict lifelong protein-restricted diet, resulting in PKU and its treatment can lead to social and financial burdens. The current study aimed to evaluate the health-related quality of life (HRQoL) of children living with PKU. PATIENTS AND METHODS: A single-centre, cross-sectional, observational study was conducted at the Center of Newborn Screening and Inherited Metabolic Disorders of Budapest, Hungary, using the PKU-quality of life (PKU-QoL) questionnaire. Responses of 59 parents and 11 teenagers were collected. Numerous aspects regarding HRQoL were analysed according to clinical compliance and severity. The patients were classified into groups with good or suboptimal adherence based on regular phenylalanine (Phe) values. The online officially translated versions of the adolescent or parental PKU-QoL questionnaire were used and analysed anonymously. Differences in HRQoL were compared - PKU vs. Hyperphenylalaninaemia (HPA) and good vs. suboptimal adherence. RESULTS: Twenty-five of 32 examined parameters had no or little impact on HRQoL. The most frequently reported symptom was irritability. Food enjoyment was the most impacted domain, with a major severity score in the adolescent group (median 62,5, IQR: 25-75). The emotional impact was scored at moderate severity by both the adolescents and parents. Classical PKU patients with good metabolic control were more frequently tired than HPA patients (0,0027). The group with poor metabolic adherence showed more frequent tiredness (p = 0,03), slow thinking (p = 0,018) and anxiety (p = 0,015). CONCLUSION: Overall, our patients showed an excellent HRQoL; most domains (29/36) were reported as little/no impacted. Worse QoL was found in patients with suboptimal metabolic control. Particular attention should be paid to the emotional health of PKU patients.

[Changes of lactate levels in diabetic ketoacidosis and in newly diagnosed type 1 diabetes mellitus]. / Laktátszintváltozások diabeteses ketoacidosisban és frissen diagnosztizált 1-es típusú diabetes mellitusban.

Introduction: It is known that lactate concentration is increased in diabetic ketoacidosis (DKA), however, the pathophysiology and kinetics of lactate changes are still unclear. Normally, L-lactate is the major form in the human body. According to previous data, also D- and L-lactate might be increased in hyperglycaemic disorders. Aim: We aimed to describe the kinetics and mechanisms of lactate concentration changes in ketoacidosis and newly diagnosed diabetes. Method: We performed a prospective study, including 5-18-year-old children with ketoacidosis (DKA, n = 13) and with newly diagnosed type 1 diabetes without ketoacidosis (T1DM, n = 6). We performed routine blood gas analysis 0-12-24-48 hours after admission, which also measured L-lactate levels. We also determined total venous serum lactate level by gas chromatography-mass spectrometry. Results: Initial plasma lactate concentration was increased in ketoacidosis as compared to the newly diagnosed diabetes group (p<0.05). After 12 h of rehydration, lactate levels were greatly reduced in ketoacidotic patients but after 24-48 h it was repeatedly increased (all p<0.01). In the 0-12 h phase, total serum lactate level was higher than L-lactate level, referring to D-lactate production. Conclusion: We described two L-lactate peaks in ketoacidosis. In the first 12 hours anaerobic glycolysis seems to have major role in hyperlactataemia. We assume that stimulated aerobic glycolysis leads to the second lactate peak. However, D-lactate is not routinely measured, it may contribute to the initial hyperlactataemia in both groups and is comparable to L-lactate production in ketoacidosis. Orv Hetil. 2019; 160(45): 1784-1790.

[Rhabdomyolysis - may it be a metabolic myopathy? Case report and diagnostic algorithm]. / Rhabdomyolysis ­ Mikor vessük fel metabolikus myopathia lehetoségét? Esetismertetés és diagnosztikus algoritmus.

We report the case of a 46-year-old female patient with recurrent rhabdomyolysis. In the background of her metabolic myopathy an inherited metabolic disorder of the fatty acid oxidation, very long-chain acyl-coenzyme A-dehydrogenase deficiency was diagnosed. The diagnosis was based on abnormal acyl-carnitine- and urine organic-acid profile in addition to low residual enzyme activity, and was confirmed by genetic testing. After introduction of dietotherapy metabolic crisis necessitating hospital admission has not occurred neither have fixed myopathic changes developed. We present here the differential diagnosis of rhabdomyolysis and exertional muscle complaints, with the metabolic myopathies in focus. The main features of fatty acid oxidation disorders are highlighted, acute and chronic managements of very long-chain acyl-coenzyme A-dehydrogenase deficiency are discussed. Metabolic myopathies respond well to treatment, so good quality of life can be achieved. However, especially in fatty acid oxidation disorders, a metabolic crisis may develop quickly and can be fatal, albeit rarely. Some of these disorders can be identified by newborn screening, but occasionally the symptoms may manifest only in adulthood. With the presentation of this case we would like to point out that in the differential diagnosis of recurrent rhabdomyolysis inherited metabolic disorders should be considered regardless of the patient's age. Orv Hetil. 2017; 158(46): 1873-1882.

Co-infection with coxsackievirus A5 and norovirus GII.4 could have been the trigger of the first episode of severe acute encephalopathy in a six-year-old child with the intermittent form of maple syrup urine disease (MSUD).

In this case study, a co-infection with coxsackievirus A5 (family Picornaviridae) and norovirus GII.4 (family Caliciviridae) was detected by RT-PCR in a faecal sample from a six-year-old girl with symptoms of severe acute encephalopathy subsequently diagnosed as the intermittent form of maple syrup urine disease (MSUD). The two co-infecting viruses, which had been detected previously, appeared to have triggered the underlying metabolic disorder. Here, we describe the genotyping of the viruses, as well as the chronological course, laboratory test results, and clinical presentation of this case, which included recurrent vomiting without diarrhoea, metabolic acidosis, unconsciousness, seizure and circulatory collapse, but with a positive final outcome.