High protein prescription in methylmalonic and propionic acidemia patients and its negative association with long-term outcome

BACKGROUND AND OBJECTIVE

Methylmalonic acidemia (MMA) and propionic acidemia (PA) are inborn errors of metabolism. While survival of MMA and PA patients has improved in recent decades, long-term outcome is still unsatisfactory. A protein restricted diet is the mainstay for treatment. Additional amino acid mixtures (AAM) can be prescribed if natural protein is insufficient. It is unknown if dietary treatment can have an impact on outcome.

DESIGN

We performed a nationwide retrospective cohort study and evaluated both longitudinal dietary treatment and clinical course of Dutch MMA and PA patients. Protein prescription was compared to the recommended daily allowances (RDA); the safe level of protein intake as provided by the World Health Organization. The association of longitudinal dietary treatment with long-term outcome was evaluated.

RESULTS

The cohort included 76 patients with a median retrospective follow-up period of 15 years (min-max: 0-48 years) and a total of 1063 patient years on a protein restricted diet. Natural protein prescription exceeded the RDA in 37% (470/1287) of all prescriptions and due to AAM prescription, the total protein prescription exceeded RDA in 84% (1070/1277). Higher protein prescriptions were associated with adverse outcomes in severely affected patients. In PA early onset patients a higher natural protein prescription was associated with more frequent AMD. In MMA vitamin B12 unresponsive patients, both a higher total protein prescription and AAM protein prescription were associated with more mitochondrial complications. A higher AAM protein prescription was associated with an increased frequency of cognitive impairment in the entire.

CONCLUSION

Protein intake in excess of recommendations is frequent and is associated with poor outcome.

Correction: Aminoacyl-tRNA synthetase deficiencies in search of common themes

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Evaluation of 11 years of newborn screening for maple syrup urine disease in the Netherlands and a systematic review of the literature: Strategies for optimization

Maple syrup urine disease (MSUD) leads to severe neurological deterioration unless diagnosed early and treated immediately. We have evaluated the effectiveness of 11 years of MSUD newborn screening (NBS) in the Netherlands (screening >72 hours, referral if both total leucine (Xle) and valine ≥400 μmol/L blood) and have explored possibilities for improvement by combining our data with a systematic literature review and data from Collaborative Laboratory Integrated Reports (CLIR). Dutch MSUD NBS characteristics and accuracy were determined. The hypothetical referral numbers in the Dutch population of additional screening markers suggested by CLIR were calculated. In a systematic review, articles reporting NBS leucine concentrations of confirmed patients were included. Our data showed that NBS of 1 963 465 newborns identified 4 MSUD patients and led to 118 false-positive referrals (PPV 3.28%; incidence 1:491 000 newborns). In literature, leucine is the preferred NBS parameter. Total leucine (Xle) concentrations (mass-spectrometry) of 53 detected and 8 false-negative patients (sampling age within 25 hours in 3 patients) reported in literature ranged from 288 to 3376 (median 900) and 42 to 325 (median 209) μmol/L blood respectively. CLIR showed increasing Xle concentrations with sampling age and early NBS sampling and milder variant MSUD phenotypes with (nearly) normal biochemical profiles are causes of false-negative NBS results. We evaluated the effect of additional screening markers and established the Xle/phenylalanine ratio as a promising additional marker ratio for increasing the PPV, while maintaining high sensitivity in the Dutch MSUD NBS.

Retrospective evaluation of the Dutch pre-newborn screening cohort for propionic acidemia and isolated methylmalonic acidemia: What to aim, expect, and evaluate from newborn screening?

Evidence for effectiveness of newborn screening (NBS) for propionic acidemia (PA) and isolated methylmalonic acidemia (MMA) is scarce. Prior to implementation in the Netherlands, we aim to estimate the expected health gain of NBS for PA and MMA. In this national retrospective cohort study, the clinical course of 76/83 Dutch PA and MMA patients, diagnosed between January 1979 and July 2019, was evaluated. Five clinical outcome parameters were defined: adverse outcome of the first symptomatic phase, frequency of acute metabolic decompensations (AMD), cognitive function, mitochondrial complications, and treatment-related complications. Outcomes of patients identified by family testing were compared with the outcomes of their index siblings. An adverse outcome due to the first symptomatic phase was recorded in 46% of the clinically diagnosed patients. Outcome of the first symptomatic phase was similar in 5/9 sibling pairs and better in 4/9 pairs. Based on the day of diagnosis of the clinically diagnosed patients and sibling pair analysis, a preliminary estimated reduction of adverse outcome due to the first symptomatic phase from 46% to 36%-38% was calculated. Among the sibling pairs, AMD frequency, cognitive function, mitochondrial, and treatment-related complications were comparable. These results suggest that the health gain of NBS for PA and MMA in overall outcome may be limited, as only a modest decrease of adverse outcomes due to the first symptomatic phase is expected. With current clinical practice, no reduced AMD frequency, improved cognitive function, or reduced frequency of mitochondrial or treatment-related complications can be expected.

A nationwide retrospective observational study of population newborn screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in the Netherlands

To evaluate the Dutch newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency since 2007, a nationwide retrospective, observational study was performed of clinical, laboratory and epidemiological parameters of patients with MCAD deficiency born between 2007 and 2015. Severe MCAD deficiency was defined by ACADM genotypes associated with clinical ascertainment, or variant ACADM genotypes with a residual MCAD enzyme activity <10%. Mild MCAD deficiency was defined by variant ACADM genotypes with a residual MCAD enzyme activity ≥10%. The prevalence of MCAD deficiency was 1/8300 (95% CI: 1/7300-1/9600). Sensitivity of the Dutch NBS was 99% and specificity ~100%, with a positive predictive value of 86%. Thirteen newborns with MCAD deficiency suffered from neonatal symptoms, three of them died. Of the 189 identified neonates, 24% had mild MCAD deficiency. The acylcarnitine ratio octanoylcarnitine (C8)/decanoylcarnitine (C10) was superior to C8 in discriminating between mild and severe cases and more stable in the first days of life. NBS for MCAD deficiency has a high sensitivity, specificity, and positive predictive value. In the absence of a golden standard to confirm the diagnosis, the combination of acylcarnitine (ratios), molecular and enzymatic studies allows risk stratification. To improve evaluation of NBS protocols and clinical guidelines, additional use of acylcarnitine ratios and multivariate pattern-recognition software may be reappraised in the Dutch situation. Prospective recording of NBS and follow-up data is warranted covering the entire health care chain of preventive and curative medicine.

Impact of newborn screening for very-long-chain acyl-CoA dehydrogenase deficiency on genetic, enzymatic, and clinical outcomes

Most infants with very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) identified by newborn screening (NBS) are asymptomatic at the time of diagnosis and remain asymptomatic. If this outcome is due to prompt diagnosis and initiation of therapy, or because of identification of individuals with biochemical abnormalities who will never develop symptoms, is unclear. Therefore, a 10-year longitudinal national cohort study of genetically confirmed VLCADD patients born before and after introduction of NBS was conducted. Main outcome measures were clinical outcome parameters, acyl-CoA dehydrogenase very long chain gene analysis, VLCAD activity, and overall capacity of long-chain fatty acid oxidation (LC-FAO flux) in lymphocytes and cultured skin fibroblasts. Median VLCAD activity in lymphocytes of 54 patients, 21 diagnosed pre-NBS and 33 by NBS was, respectively, 5.4% (95% confidence interval [CI]: 4.0-8.3) and 12.6% (95% CI: 10.7-17.7; P < 0.001) of the reference mean. The median LC-FAO flux was 33.2% (95% CI: 22.8-48.3) and 41% (95% CI: 40.8-68; P < 0.05) of the control mean, respectively. Clinical characteristics in 23 pre-NBS and 37 NBS patients revealed hypoglycemic events in 12 vs 2 patients, cardiomyopathy in 5 vs 4 patients and myopathy in 14 vs 3 patients. All patients with LC-FAO flux <10% developed symptoms. Of the patients with LC-FAO flux >10% 7 out of 12 diagnosed pre-NBS vs none by NBS experienced hypoglycemic events. NBS has a clear beneficial effect on the prevention of hypoglycemic events in patients with some residual enzyme activity, but does not prevent hypoglycemia nor cardiac complications in patients with very low residual enzyme activity. The effect of NBS on prevalence and prevention of myopathy-related complications remains unclear.

Clinical, biochemical, and molecular overview of transaldolase deficiency and evaluation of the endocrine function: Update of 34 patients

BACKGROUND

Transaldolase deficiency (TALDO-D) is a rare autosomal recessive inborn error of the pentose phosphate pathway. Since its first description in 2001, several case reports have been published, but there has been no comprehensive overview of phenotype, genotype, and phenotype-genotype correlation.

METHODS

We performed a retrospective questionnaire and literature study of clinical, biochemical, and molecular data of 34 patients from 25 families with proven TALDO-D. In some patients, endocrine abnormalities have been found. To further evaluate these abnormalities, we performed biochemical investigations on blood of 14 patients.

RESULTS AND CONCLUSIONS

Most patients (n = 22) had an early-onset presentation (prenatally or before 1 month of age); 12 patients had a late-onset presentation (3 months to 9 years). Main presenting symptoms were intrauterine growth restriction, dysmorphic facial features, congenital heart disease, anemia, thrombocytopenia, and hepato(spleno)megaly. An older sib of two affected patients was asymptomatic until the age of 9 years, and only after molecular diagnosis was hepatomegaly noted. In some patients, there was gonadal dysfunction with low levels of testosterone and secondary luteinizing hormone (LH) and follicle-stimulating hormone (FSH) abnormalities later in life. This overview provides information that can be helpful for managing patients and counseling families regarding prognosis. Diagnostic guidelines, possible genotype-phenotype correlations, treatment options, and pathophysiological disease mechanisms are proposed.

Proposal for an individualized dietary strategy in patients with very long-chain acyl-CoA dehydrogenase deficiency

BACKGROUND

Patients with very long chain acyl-CoA dehydrogenase deficiency (VLCADD), a long chain fatty acid oxidation disorder, are traditionally treated with a long chain triglyceride (LCT) restricted and medium chain triglyceride (MCT) supplemented diet. Introduction of VLCADD in newborn screening (NBS) programs has led to the identification of asymptomatic newborns with VLCADD, who may have a more attenuated phenotype and may not need dietary adjustments.

OBJECTIVE

To define dietary strategies for individuals with VLCADD based on the predicted phenotype.

METHOD

We evaluated long-term dietary histories of a cohort of individuals diagnosed with VLCADD identified before the introduction of VLCADD in NBS and their beta-oxidation (LC-FAO) flux score (rate of oleate oxidation) in cultured skin fibroblasts in relation to the clinical outcome. Based on these results a dietary strategy is proposed.

RESULTS

Sixteen individuals with VLCADD were included. One had an LC-FAO flux score >90%, was not on a restricted diet and is asymptomatic to date. Four patients had an LC-FAO flux score <10%, and significant VLCADD related symptoms despite the use of strict diets including LCT restriction, MCT supplementation and nocturnal gastric drip feeding. Patients with an LC-FAO flux score between 10 and 90% (n = 11) showed a more heterogeneous phenotype.

CONCLUSIONS

This study shows that a strict diet cannot prevent poor clinical outcome in severely affected patients and that the LC-FAO flux is a good predictor of clinical outcome in individuals with VLCADD identified before its introduction in NBS. Hereby, we propose an individualized dietary strategy based on the LC-FAO flux score.

Aminoacyl-tRNA synthetase deficiencies in search of common themes

Purpose

Pathogenic variations in genes encoding aminoacyl-tRNA synthetases (ARSs) are increasingly associated with human disease. Clinical features of autosomal recessive ARS deficiencies appear very diverse and without apparent logic. We searched for common clinical patterns to improve disease recognition, insight into pathophysiology, and clinical care.

Methods

Symptoms were analyzed in all patients with recessive ARS deficiencies reported in literature, supplemented with unreported patients evaluated in our hospital.

Results

In literature, we identified 107 patients with AARS, DARS, GARS, HARS, IARS, KARS, LARS, MARS, RARS, SARS, VARS, YARS, and QARS deficiencies. Common symptoms (defined as present in ≥4/13 ARS deficiencies) included abnormalities of the central nervous system and/or senses (13/13), failure to thrive, gastrointestinal symptoms, dysmaturity, liver disease, and facial dysmorphisms. Deep phenotyping of 5 additional patients with unreported compound heterozygous pathogenic variations in IARS, LARS, KARS, and QARS extended the common phenotype with lung disease, hypoalbuminemia, anemia, and renal tubulopathy.

Conclusion

We propose a common clinical phenotype for recessive ARS deficiencies, resulting from insufficient aminoacylation activity to meet translational demand in specific organs or periods of life. Assuming residual ARS activity, adequate protein/amino acid supply seems essential instead of the traditional replacement of protein by glucose in patients with metabolic diseases.

Evaluation of the outcome of CT and MR imaging in pediatric patients with bilateral sensorineural hearing loss

OBJECTIVE

To evaluate the clinically relevant abnormalities as visualized on CT and MR imaging in children with symmetric and asymmetric bilateral sensorineural hearing loss (SNHL), in relation to age and the severity of hearing loss.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral otology and audiology center.

PATIENTS AND DIAGNOSTIC INTERVENTIONS

From January 2006 until January 2016, a total of 207 children diagnosed with symmetric and asymmetric bilateral SNHL were included. They underwent CT and/or MR imaging for the evaluation of the etiology of their hearing loss.

MAIN OUTCOME MEASURES

Radiologic abnormalities associated with SNHL.

RESULTS

302 scans were performed in 207 children (median age of 0.8 years old) with bilateral SNHL. The most frequently identified cause of bilateral SNHL was a malformation of the labyrinth. The combined diagnostic yield of CT and MR imaging was 32%. The diagnostic yield of MR (34%) was considerably higher than that of CT (20%). We found a higher rate of abnormalities in children with profound hearing loss (41%) compared to milder hearing loss (8-29%), and in asymmetric SNHL (52%) compared to symmetric SNHL (30%).

CONCLUSION

Imaging is essential in the etiologic evaluation of children with bilateral SNHL. The highest diagnostic yield is found in children with bilateral asymmetric SNHL or profound SNHL. Based on our findings, MR is the primary imaging modality of choice in the etiological evaluation of children with bilateral SNHL because of its high diagnostic yield.

High prevalence of abnormalities on CT and MR imaging in children with unilateral sensorineural hearing loss irrespective of age or degree of hearing loss

OBJECTIVE

Evaluation of causal abnormalities identified on CT and MR imaging in children with unilateral sensorineural hearing loss (USNHL), and the association with age and severity of hearing loss.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral otology/audiology center.

PATIENTS AND DIAGNOSTIC INTERVENTIONS

102 children diagnosed with USNHL between 2006 and 2016 were included. They underwent CT and/or MR imaging for the evaluation of the etiology of their hearing loss.

MAIN OUTCOME MEASURES

Radiologic abnormalities of the inner ear and brain associated with USNHL.

RESULTS

Using CT and/or MR imaging, causal abnormalities were identified in 49%, which is higher than previously reported (25-40%). The most frequently affected site was the labyrinth (29%), followed by the cochlear nerve (9%) and brain (7%). No significant difference in the number or type of abnormalities was found for the degree of hearing loss or age categories.

CONCLUSIONS

Imaging is essential in the etiologic analysis of USNHL because of the high prevalence of causative abnormalities that can be identified with radiology, irrespective of the patients' age or degree of hearing loss. CT and MR imaging are complementary imaging options. The ideal imaging algorithm is controversial. Based on our findings, we conclude that there is limited additional diagnostic value of simultaneous dual modality imaging over sequential diagnostics. We therefore perform a stepwise radiological workup in order to maximize the diagnostic yield while minimizing impact and costs. If the primary imaging modality does not identify a cause for USNHL, performing the alternative imaging modality should be considered.

LEVEL OF EVIDENCE

Retrospective cohort study 2b.

Pain: a prevalent feature in patients with mucopolysaccharidosis. Results of a cross-sectional national survey

BACKGROUND

While clinical observations suggest that many patients with mucopolysaccharidosis (MPS) experience chronic pain, few studies have assessed its extent and impact. We therefore investigated its prevalence in patients with all types of MPS in the Netherlands. We also examined the association between pain and health related quality of life (HRQoL) and other clinical variables.

METHODS

We conducted a nationwide MPS survey that used questionnaires on MPS and disease-related symptoms (MPS-specific questionnaire), developmental level (Vineland Screener 0-6 years), quality of life (PedsQl and SF-36), and disability (Childhood Health Assessment Questionnaire). Depending on their age and developmental level, patients or their parents were asked to assess pain by keeping a pain diary for five consecutive days: either the Non-communicating Children's Pain Checklist - Revised (3-18 years intellectually disabled and children <8 years), the VAS-score (> 18 years), or the Faces Pain Scale - Revised (8-18 years).

RESULTS

Eighty-nine MPS patients were invited, 55 of whom agreed to participate (response rate 62 %; median age 10.9 years, range 2.9-47.2 years). They covered a wide spectrum in all age groups, ranging from no pain to severe pain. Forty percent scored above the cut-off value for pain. Most reported pain sites were the back and hips. While the MPS III group experienced the highest frequency of pain (52.9 %), 50 % of patients with an intellectual disability seemed to experience pain, versus 30 % of patients with a normal intelligence. MPS patients scored much lower (i.e., more pain) than a random sample of the Dutch population on the bodily pain domain of the SF-36 scale and the PedsQl.

CONCLUSION

With or without intellectual disabilities, many MPS patients experience pain. We recommend that standardized pain assessments are included in the regular follow-up program of patients with MPS.

Growth in patients with mucopolysaccharidosis type III (Sanfilippo disease)

BACKGROUND

Mucopolysaccharidosis III (MPS III), known as Sanfilippo disease, is a lysosomal storage disorder mainly characterized by progressive neurodegeneration with cognitive decline and relatively attenuated somatic signs and symptoms. Although short stature is invariably present in patients with the other mucopolysaccharidoses, it has not been sufficiently addressed in MPS III. The aim of this study was to investigate growth data of a large Dutch MPS III cohort in order to construct growth charts for MPS III patients.

METHODS

Height, weight, head circumference (HC), and body mass index (BMI) data from 118 MPS III patients were used to construct reference curves, using the lambda, mu, sigma (LMS) method. Genotype-group comparisons for height standard deviation scores (SDS) were performed by Kruskal-Wallis analysis for different age groups.

RESULTS

Birth weight and length were within normal ranges for gestational age and showed a significantly stunted growth from age 6 years onward. Mean final heights were 169.7 cm (-2.0 SDS) and 165.4 cm (-0.84 SDS) for adult male and female, patients, respectively. Phenotypic severity, as assessed by genotyping, correlated with growth pattern and final height. In addition, mean BMI and HC SDS were significantly higher when compared with Dutch standards for both boys and girls.

CONCLUSIONS

Growth in MPS III is stunted mainly in patients with the severe phenotype. We provide disease-specific growth references that can be used for clinical management of MPS III patients and may be of value for future treatment studies.

Evaluation of quality of life in PKU before and after introducing tetrahydrobiopterin (BH4); a prospective multi-center cohort study

BACKGROUND

Phenylketonuria (PKU) is a rare inborn error of metabolism caused by phenylalanine hydroxylase enzyme (PAH) deficiency. Treatment constitutes a strict Phe restricted diet with unpalatable amino acid supplements. Residual PAH activity enhancement with its cofactor tetrahydrobiopterin (BH4) is a novel treatment which increases dietary tolerance in some patients and permits dietary relaxation. Relaxation of diet may improve health related quality of life (HRQoL). This prospective cohort study aims to evaluate HRQoL of patients with PKU and effects of BH4 treatment on HRQoL.

METHODS

Patients aged 4years and older, diagnosed through newborn screening and early and continuously treated, were recruited from eight metabolic centers. Patients and mothers completed validated generic and chronic health-conditions HRQoL questionnaires (PedsQL, TAAQOL, and DISABKIDS) twice: before and after testing BH4 responsivity. Baseline results were compared to the general population. Data collected after BH4 testing was used to find differences in HRQoL between BH4 unresponsive patients and BH4 responsive patients after one year of treatment with BH4. Also a within patient comparison was performed to find differences in HRQoL before and after treatment with BH4.

RESULTS

69/81 (85%) patients completed the questionnaires before BH4 responsivity testing, and 45/69 (65%) participated again after testing. Overall PKU patients demonstrated normal HRQoL. However, some significant differences were found when compared to the general population. A significantly higher (thus better) score on the PedsQL was reported by children 8-12 years on physical functioning and by children 13-17 years on total and psychosocial functioning. Furthermore, adult patients reported significantly lower (thus worse) scores in the TAAQOL cognitive domain. 10 patients proved to be responsive to BH4 treatment; however improvement in their HRQoL after relaxation of diet could not be demonstrated.

Acid sphingomyelinase (Asm) deficiency patients in The Netherlands and Belgium: disease spectrum and natural course in attenuated patients

Niemann-Pick disease (NPD) is a neurovisceral lysosomal storage disorder caused by acid sphingomyelinase (ASM) deficiency, which can be categorized as either Niemann-Pick disease type A [NPD-A], with progressive neurological disease and death in early childhood, or as Niemann-Pick disease type B [NPD-B], with a more variable spectrum of manifestations. Enzyme replacement therapy (ERT) with recombinant sphingomyelinase is currently studied as potential treatment for NPD-B patients. The objective of this study is to characterize the clinical features of patients with ASM deficiency in the Netherlands and Belgium with focus on the natural disease course of NPD-B patients. Prospective and retrospective data on ASM deficient patients were collected in The Netherlands and part of Belgium. Patients with NPD-B that could be followed prospectively were evaluated every 6-12 months for pulmonary function tests, 6 minute walk test (6 MWT), imaging (bone marrow infiltration measured by QCSI, organ volumes by MRI and CT scan of the lungs) and biochemical markers. Twenty-five patients with ASM deficiency were identified (13 males, 12 females, median age 13years, range 1-59 years). Nine patients had died at the time of the study, including four NPD-A patients at the age of 1,1, 2, 3 and five NPDB patents at the age of 5, 6, 43, 56 and 60 years. There was a high prevalence of homozygosity and compound heterozygosity for the common p.Arg608del mutation in 43% and 19% of NPD-B patients, respectively. In NPD-B patients, thrombocytopenia was present in most, while anemia and leucopenia were less common (33% and 6 % respectively). HDL cholesterol was reduced in most patients. Pulmonary disease was severe in several patients. Follow-up up to 11 years revealed a gradual decrease in platelet count. Detailed investigations in 6 NPD-B patients with follow-up in 4 patients revealed remarkable stable disease parameters up to 6 years, with some decline in pulmonary function and 6 MWT. Bone marrow fat fractions were decreased, indicating the presence of storage macrophages. Lung involvement was not related to the extent of visceromegaly, cytopenia or bone marrow involvement. In conclusion, in NPD-B patients pulmonary disease is the most debilitating feature. Disease manifestations are mostly stable in attenuated patients. Bone marrow infiltration is a less prominent feature of the disease.

Risk stratification by residual enzyme activity after newborn screening for medium-chain acyl-CoA dehyrogenase deficiency: data from a cohort study

Background

Since the introduction of medium-chain acyl coenzyme A dehydrogenase (MCAD) deficiency in population newborn bloodspot screening (NBS) programs, subjects have been identified with variant ACADM (gene encoding MCAD enzyme) genotypes that have never been identified in clinically ascertained patients. It could be hypothesised that residual MCAD enzyme activity can contribute in risk stratification of subjects with variant ACADM genotypes.

Methods

We performed a retrospective cohort study of all patients identified upon population NBS for MCAD deficiency in the Netherlands between 2007–2010. Clinical, molecular, and enzymatic data were integrated.

Results

Eighty-four patients from 76 families were identified. Twenty-two percent of the subjects had a variant ACADM genotype. In patients with classical ACADM genotypes, residual MCAD enzyme activity was significantly lower (median 0%, range 0-8%) when compared to subjects with variant ACADM genotypes (range 0-63%; 4 cases with 0%, remainder 20-63%). Patients with (fatal) neonatal presentations before diagnosis displayed residual MCAD enzyme activities <1%. After diagnosis and initiation of treatment, residual MCAD enzyme activities <10% were associated with an increased risk of hypoglycaemia and carnitine supplementation. The prevalence of MCAD deficiency upon screening was 1/8,750 (95% CI 1/7,210–1/11,130).

Conclusions

Determination of residual MCAD enzyme activity improves our understanding of variant ACADM genotypes and may contribute to risk stratification. Subjects with variant ACADM genotypes and residual MCAD enzyme activities <10% should be considered to have the same risks as patients with classical ACADM genotypes. Parental instructions and an emergency regimen will remain principles of the treatment in any type of MCAD deficiency, as the effect of intercurrent illness on residual MCAD enzyme activity remains uncertain. There are, however, arguments in favour of abandoning the general advice to avoid prolonged fasting in subjects with variant ACADM genotypes and >10% residual MCAD enzyme activity.

Nephrological abnormalities in patients with transaldolase deficiency

BACKGROUND

Transaldolase deficiency (OMIM 606003) is a multisystem disorder first described in 2001. Transaldolase is an enzyme of the reversible part of the pentose phosphate pathway. Affected patients have abnormal polyol concentrations in body fluids, mostly in urine. The clinical presentation is variable. The leading symptoms are coagulopathy, thrombocytopenia, hepatosplenomegaly, hepatic fibrosis and dysmorphic features. The objective of our study was to attempt to characterize the renal phenotype of patients with transaldolase deficiency.

METHODS

Clinical and laboratory data of all nine patients with transaldolase deficiency presently known were gathered by retrospective chart analysis.

RESULTS

Nephrological abnormalities were present in seven of the nine patients. The most common findings were low molecular weight (LMW) proteinuria and hypercalciuria. The two oldest patients had moderate chronic kidney failure. In two patients, generalized aminoaciduria was found, two patients had renal phosphate wasting and three patients had hyperchloremic metabolic acidosis. Three patients had anatomical abnormalities.

CONCLUSIONS

Renal tubular dysfunction is present in the majority of patients with transaldolase deficiency and may lead to chronic renal failure. The combination of unexplained liver dysfunction with LMW proteinuria should prompt metabolic screening for transaldolase deficiency by measuring urinary polyols. In patients with transaldolase deficiency, monitoring of kidney function is mandatory.

A case of tubulointerstitial nephritis in a patient with an influenza H1N1 infection

BACKGROUND

Patients suffering from an H1N1 infection mainly suffer from respiratory symptoms but may also develop symptoms in other organ systems, such as the kidneys.

CASE-DIAGNOSIS/TREATMENT

A 4 ½ year-old boy was admitted with relatively mild respiratory symptoms of H1N1 infection, but developed severe generalized proximal tubular dysfunction with sterile leucocyturia and a reversible rise in serum creatinine. He made a full recovery with supportive therapy.

CONCLUSION

Influenza H1N1 may be associated with acute tubulointerstitial nephritis.

4-Hydroxybutyric aciduria associated with catheter usage: a diagnostic pitfall in the identification of SSADH deficiency

Succinic semialdehyde dehydrogenase deficiency is a slowly progressive to static neurological disorder featuring elevated concentrations of 4-hydroxybutyric acid in body fluids. We present two patients with elevated 4-hydroxybutyric acid in urine which was later shown to be linked to catheter usage.

Chronological changes of the amplitude-integrated EEG in a neonate with molybdenum cofactor deficiency

Molybdenum cofactor (Moco) deficiency is a rare neurometabolic disorder, characterized by neurological impairment and refractive seizures, due to toxic accumulation of sulfite in the brain. Earlier it was suggested that in Moco-deficient humans maternal clearance of neurotoxic metabolites prevents prenatal brain damage. However, limited data are available about the time profile in which neurophysiologic deterioration occurs after birth. The amplitude-integrated electroencephalography (aEEG) is a bedside method in neonates to monitor cerebral recovery after hypoxic-ischemic insults, detect epileptic activity, and evaluate antiepileptic drug treatment. We describe a chronological series of changes in aEEG tracings in a neonate with Moco deficiency. He presented with myoclonic spasms and hypertonicity a few hours after birth, however, the aEEG pattern was still normal. Within 2 days, the aEEG rapidly changed into a burst suppression pattern with repetitive seizures. After antiepileptic treatment, the aEEG remained abnormal. In this patient, the normal aEEG pattern at birth may have been due to maternal clearance of sulfite in utero. After birth, accumulation of sulfite causes progressive brain damage, reflected by the progressive depression of the aEEG tracings. This is in agreement with the results from a Moco-deficient mouse model, suggesting that maternal sulfite clearance suppresses prenatal brain damage. To our knowledge, this is the first case report describing the chronological changes in the aEEG pattern in a Moco-deficient patient. Insight into the time profile in which neurologic deterioration in Moco-deficient humans occurs is essential, especially when potential treatment strategies are being evaluated.

Mutations in CCBE1 cause generalized lymph vessel dysplasia in humans

Lymphedema, lymphangiectasias, mental retardation and unusual facial characteristics define the autosomal recessive Hennekam syndrome. Homozygosity mapping identified a critical chromosomal region containing CCBE1, the human ortholog of a gene essential for lymphangiogenesis in zebrafish. Homozygous and compound heterozygous mutations in seven subjects paired with functional analysis in a zebrafish model identify CCBE1 as one of few genes causing primary generalized lymph-vessel dysplasia in humans.

Hydrops fetalis and early neonatal multiple organ failure in familial hemophagocytic lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (FHLH) is a genetic heterogeneous autosomal recessive disorder. We report two siblings with FHLH caused by a PRF1 mutation. The first child died in utero with hydrops fetalis and the second presented soon after birth with fatal multiple organ failure. Post-mortem DNA analysis showed a homozygous c.666C>A (p.His222Gln) mutation in the PRF1 gene in both cases, with their non-consanguineous parents being heterozygous for the same mutation. Review of the literature shows that perinatal presentation of FHLH is rare. Diagnosis is difficult because in most cases histologic examination reveals no hemophagocytosis and the disease is rapidly fatal. The association between hydrops fetalis and FHLH has been reported in four previous reports. We present the first case of hydrops fetalis caused by FHLH, confirmed by DNA analysis. FHLH should be included in the differential diagnosis of non-immune hydrops fetalis and neonatal multiple organ failure.

Phenylalanine tolerance can already reliably be assessed at the age of 2 years in patients with PKU

BACKGROUND

The clinical severity of phenylalanine hydroxylase deficiency is usually defined by either pre-treatment phenylalanine (Phe) concentration or Phe tolerance at 5 years of age. So far, little is known about the course of Phe tolerance or the ability of both pre-treatment Phe and Phe tolerance at early age to predict Phe tolerance at later age.

AIM

This study was conducted to investigate the course of the individual Phe tolerance and to assess the predictive value of both the pre-treatment Phe concentration and Phe tolerance at 1 and 6 months and 1, 2, 3 and 5 years for Phe tolerance at 10 years of age.

METHOD

Data on blood Phe concentration, prescribed Phe intake and weight of 213 early and continuously treated Dutch PKU patients up to 10 years of age were collected. Data acquired under good metabolic control were used in the study. Tolerance was expressed in mg/day and mg/kg per day.

RESULTS

Data at 1 and 6 months and at 1, 2, 3 and 5 years of 61, 58, 59, 57, 56 and 59 patients were included for comparison with the Phe tolerance at 10 years. Phe tolerances (mg/kg per day) at 2, 3 and 5 years showed a clear correlation with the tolerance at 10 years of age (r = 0.608, r = 0.725 and r = 0.661). Results for tolerance expressed as mg/day were comparable. Pre-treatment Phe concentrations did not correlate significantly with the tolerance.

CONCLUSION

Pre-treatment Phe is unreliable but Phe tolerance is a reliable predictor of the tolerance at 10 years of age, starting at 2 years of age.

The intake of total protein, natural protein and protein substitute and growth of height and head circumference in Dutch infants with phenylketonuria

In a previous study, Dutch children with phenylketonuria (PKU) were found to be slightly shorter than their healthy counterparts. In the literature, it has been hypothesized that a higher protein intake is necessary to optimize growth in PKU patients. The study aimed to investigate whether protein intake (total, natural and protein substitute) in this group might be an explanatory factor for the observed growth. Growth of height and head circumference and dietary data on protein intake (total, natural and protein substitute) from 174 Dutch PKU patients born between 1974 and 1996 were analysed retrospectively for the patients' first 3 years of life. Analyses were corrected for energy intake during the first year of life and for the clinical severity of the deficiency of phenylalanine hydroxylase by means of plasma phenylalanine concentration at birth. Neither protein nor energy intake correlated with height growth. A positive, statistically significant relation between head circumference growth and natural protein and total protein intake was found, but not with the intake of the protein substitute or energy. Therefore, this study suggests that improvement of the protein substitute rather than an increase of total protein intake may be important in optimizing head circumference growth in PKU patients.

Clearance of maternal leukaemic cells in a neonate

A 36-week pregnant woman was diagnosed with acute lymphoblastic leukaemia. Delivery was initiated prematurely, and a healthy child was born. Cord blood and peripheral blood samples from the neonate (obtained at 6 weeks, 3 months and 6 months) were analysed for the presence of minimal residual disease by polymerase chain reaction analysis of a leukaemia-specific IGH gene rearrangement and the E2A--PBX1 fusion gene transcript. In the cord blood sample, a tumour load of approximately 4 x 10(-4) was found, whereas all later blood samples were negative. Our data indicate that the maternal leukaemic cells did not engraft in the neonate.

The fall of cardiac output in endotoxemic rats cannot explain all changes in organ blood flow: a comparison between endotoxin and low venous return shock

During endotoxin shock mean arterial pressure (MAP) and cardiac output (CO) fall, and the latter is redistributed. To evaluate whether these changes are solely caused by the low output, or are also based on endotoxin itself, we compared regional hemodynamic changes during endotoxemia with those in a nonendotoxemic state of decreased CO in anesthetized rats. In group E (n = 10) endotoxin Escherichia coli O127:B8 (8 mg.kg-1) was infused from t = 0 till t = 60 min. In group B (n = 10) the same decrease of CO and MAP was obtained as in group E by inflating a balloon in the inferior caval vein, distal to the renal veins, from t = 0 till t = 60 min. We measured MAP, CO (thermodilution), central venous pressure, heart rate, organ blood flow, and redistribution of CO (microspheres), arterial lactate and glucose, and hematocrit. MAP and CO decreased (p < .05) in both groups (by 30 and 50%, respectively at t = 60). Heart rate, hematocrit, arterial lactate, and arterial glucose were significantly higher (p < .05) in group E (by 17, 12, 180, and 55%, respectively). Blood flow to most organs had similarly decreased in both groups. The decreased intestinal blood flow lead to macroscopic damage only in group E. Blood flows (absolute or as percentage of CO) to heart, hepatic artery, and diaphragm, however, had significantly increased in group E while blood flows to skin, skeletal muscle, and stomach had decreased more in group E. Except for the heart these differences could be explained by increased work load (detoxification: liver; hyperventilation: diaphragm, muscle) and thus to a more pronounced redistribution at the expense of skin and muscle blood flow. Regional hemodynamic changes during endotoxemia thus could largely be attributed to decrease of CO and redistribution of the circulating blood volume. In the heart, endotoxin seemed to exert effects independent of the hypodynamic state. This was also true for the intestinal damage and the rise in hematocrit and arterial lactate.

Protective role of NO in the regional hemodynamic changes during acute endotoxemia in rats

The role of NO during the first hour of endotoxemia is still controversial. To evaluate whether NO is protective or detrimental to the regulation of systemic blood pressure, cardiac output (CO), and organ perfusion in rats during acute endotoxemia, we have studied the effects of inhibition of NO synthesis. Thirty minutes after 0.1 mg NG-nitro-L-arginine (L-NNA; group L, n = 7, partial inhibition), 1 mg L-NNA (group H, n = 6, complete inhibition), or saline (group E, n = 7) intravenous infusion, anesthetized volume-loaded rats were infused with endotoxin Escherichia coli O127:B8 (8 mg.kg-1 x h-1) from time (t) = 0 to 60 min. Organ blood flow was measured with radioactive microspheres. In group H, at time 0, CO was lower than in group E (by -29%; P < 0.05), and systemic vascular resistance (SVR) was higher than in groups E and L (by 72 and 51%, respectively; P < 0.05). Perfusion of the pancreas, stomach, intestines, and kidney was lower (P < 0.05) and corresponding organ vascular resistance (OVR) higher (P < 0.05) in group H than in groups E and L (except kidney in group L). At t = 60 min, in groups H and L, CO was lower (by -45 and -26%, respectively; P < 0.05) and SVR was higher (by 112 and 54%, respectively; P < 0.05) than in group E. In group L only blood flow to the heart, pancreas, intestines, and kidney was significantly lower than in group E, and corresponding OVR was higher.(ABSTRACT TRUNCATED AT 250 WORDS)

High-energy phosphates in heart, liver, kidney, and skeletal muscle of endotoxemic rats

Endotoxemia can affect the storage of high-energy phosphates [ATP, creatine phosphate (CrP)] even in organs in which global blood flow does not fall. If a decrease in this storage is due to an inadequate oxygen supply-to-demand ratio, improving the perfusion should restore it. Therefore, in anesthetized endotoxemic rats we studied organ perfusion and the storage of high-energy phosphates of heart, liver, kidney, and skeletal muscle and measured the effects of improving cardiac output (CO) and organ blood flow with cardiostimulatory drugs [dopexamine (DX) and dobutamine (DB)]. Endotoxin (Escherichia coli O127.B8, 8 mg/kg) was infused from 0 to 60 min in three groups of anesthetized rats: one untreated (saline only) group (ES; n = 10), and two groups in which we infused DX (3 x 10(-8) mol.kg-1.min-1; n = 10) or DB (10(-7) mol.kg-1.min-1; n = 8) from 60 to 135 min. A fourth group served as time-matched controls (C; n = 8). Organ blood flows at 0 and 135 min (end of experiment) were measured with radioactive microspheres. In biopsies (at 135 min) we measured lactate, ATP, and CrP concentrations. Endotoxemia decreased CO (45% at 135 min; P < 0.05), which could be restored by DX and DB. Myocardial and skeletal muscle blood flow and ATP did not differ in the groups at 135 min. Hepatic and renal blood flow decreased in the ES group 44 and 52%, respectively (P < 0.05); DX restored the fall of hepatic and DB of renal blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic and regional hemodynamic changes during endotoxin or platelet activating factor (PAF)-induced shock in rats

To evaluate the role of platelet activating factor (PAF) during endotoxin shock, we compared its effects with those of endotoxin. We measured arterial pressure (MAP), heart rate (HR), cardiac output (CO; thermodilution), arterial lactate (Calact), organ blood flow (radioactive microspheres), and organ vascular resistance in four groups of anesthetized (pentobarbital) male Wistar rats (n = 7 per group), infused from t = 0 to t = 60 min with saline (group C: time matched control), endotoxin Escherichia coli O127:B8, 8 mg.kg-1 (group E), a "low PAF dose" (1 microgram.kg-1) to cause the same decrease in MAP as in group E (group PL), or a "high PAF dose" (3 micrograms.kg-1) to cause the same decrease in CO as in group E (group PH). At t = 60 min, MAP had decreased by 33% in E and PL, and by 55% in PH group. CO had decreased by 41% in the E and PH group. Calact had increased in the E and PH group by 300 and 200%, respectively. In the E, PL and PH group, coronary vascular resistance decreased. In the splanchnic organs, endotoxin caused a decrease in blood flow due to vasoconstriction, whereas PAF (both concentrations) caused vasodilation (except for spleen). Renal vascular resistance decreased (P < 0.05) in the PL group. In all groups, vascular resistance had increased (P < 0.05) in skin, and not changed in skeletal muscle (P < 0.05). Thus, hemodynamic changes after PAF infusion were partially similar to those after endotoxin infusion (coronary vasodilation and vasoconstriction in spleen and skin).(ABSTRACT TRUNCATED AT 250 WORDS)

Organ blood flow and distribution of cardiac output in dopexamine- or dobutamine-treated endotoxemic rats

Endotoxemia causes a decrease of blood flow to most organs. If this could be prevented, chances of survival might improve. In endotoxemic rats, we studied the effect of a therapeutic infusion of dopexamine (dopaminergic, beta 2-adrenergic) on blood flow and percentage of the cardiac output distributed to heart, brain, hepatic artery, stomach, intestines, spleen, pancreas, kidneys, adrenals, diaphragm, skeletal muscle, and skin. Dopexamine action was compared with that of dobutamine (beta 1-adrenergic). Endotoxin shock was induced in 28 rats with infusion of 8 mg/kg Escherichia coli O127:B8 endotoxin from 0 to 60 minutes; the rats were then divided into 3 groups, which received from 60 to 135 minutes of an infusion of saline (ES; n = 10), dopexamine hydrochloride (DX, 3 x 10(-8) mol/kg.min; n = 10) or dobutamine (DB, 10(-7) mol/kg.min; n = 8). A fourth group served as time-matched controls (C, saline from 0 to 135 minutes; n = 8). In the untreated endotexemic rats, cardiac output decreased and organ blood flow decreased except in the diaphragm, heart, and brain; the percentage of the cardiac output to those organs increased. Dopexamine and dobutamine similarly improved cardiac output in endotoxemic rats. All organs benefitted to the same extent from the increased cardiac output. Therapeutic infusion of dopexamine during endotoxemia did not favor flow to any particular organ; redistribution of cardiac output changed little after administration of dopexamine, and its effects were not significantly different from those of dobutamine.

[The effect of age and activity on arterial oxygen pressure and arterial oxygen saturation in hospitalized patients]

In order to obtain adequate normal values for arterial blood gas values, the effect of aging and activity was investigated by cross-sectional selection in an in-patient population of 108 patients aged between 20 and 90 years. The patients were free of pulmonary, cardiac and metabolic disease. Smoking and obesity were tolerated up to specified limits. Arterial blood was obtained during standardised resting and active states. The results show a clinically important and highly significant (p less than 0.001) decline of the oxygen tension (PaO2) with age and also a considerable effect of minor activity (p less than 0.01) on blood gas values. However, the relationship of both oxygen tension and oxygen saturation with age is not a linear function as suggested in previous studies. For the interpretation of arterial oxygen tension values or to define hypoxaemia, only normal values related to age and activity should be used. In the elderly, low levels of PaO2 are encountered regularly. Determination of the oxygen saturation may be helpful, especially in differentiating between a normal and a pathological state.