[Show abstract][Hide abstract] ABSTRACT: Congenital lactase deficiency is an extremely rare gastrointestinal disorder characterized by neonatal-onset watery diarrhoea and failure to thrive. We present the first genetically confirmed case of congenital lactase deficiency in Central Europe.
After an uneventful pregnancy and birth, a male newborn of consanguineous parents of Turkish origin presented with watery diarrhoea. On day 17, he was admitted to hospital with weight loss, hypertonic dehydration, and metabolic acidosis. Additionally, the patient showed an elevated calcium concentration in blood and urine as well as nephrocalcinosis. Diarrhoea stopped during intravenous rehydration and when feeding a glucose-, galactose-, and lactose-free formula. Therefore, glucose-galactose-malabsorption was assumed. However, genetic testing of the SGLT1 (SLC5A1) gene was negative and, indeed, feeding maltodextrine did not result in recurrence of diarrhoea. In contrast, lactose feeding immediately caused watery diarrhoea, suggesting congenital lactase deficiency. Genetic testing of the LCT gene revealed homozygosity for a 1-bp deletion in exon 8 (c.3448delT). Because of the nature of the mutation, causing a frame shift and a premature termination of translation, congenital lactase deficiency was confirmed and intestinal biopsies were unnecessary. The patient's general condition improved substantially on a lactose-free diet, including hypercalcaemia, hypercalciuria, and nephrocalcinosis which, however, only disappeared after months.
This case demonstrates (a) that congenital lactase deficiency should be considered in cases of severe neonatal diarrhoea, (b) that intestinal biopsies can be avoided in typical cases that are confirmed by genetic testing, and
(c) that the associated nephrocalcinosis can be reversed on diet and an appropriate fluid management.
[Show abstract][Hide abstract] ABSTRACT: Pediatric movement disorders are still a diagnostic challenge, as many patients remain without a (genetic) diagnosis. Magnetic resonance imaging (MRI) pattern recognition can lead to the diagnosis. MEGDEL syndrome (3-MethylGlutaconic aciduria, Deafness, Encephalopathy, Leigh-like syndrome MIM #614739) is a clinically and biochemically highly distinctive dystonia deafness syndrome accompanied by 3-methylglutaconic aciduria, severe developmental delay, and progressive spasticity. Mutations are found in SERAC1, encoding a phosphatidylglycerol remodeling enzyme essential for both mitochondrial function and intracellular cholesterol trafficking. Based on the homogenous phenotype, we hypothesized an accordingly characteristic MRI pattern. A total of 43 complete MRI studies of 30 patients were systematically reevaluated. All patients presented a distinctive brain MRI pattern with five characteristic disease stages affecting the basal ganglia, especially the putamen. In stage 1, T2 signal changes of the pallidum are present. In stage 2, swelling of the putamen and caudate nucleus is seen. The dorsal putamen contains an "eye" that shows no signal alteration and (thus) seems to be spared during this stage of the disease. It later increases, reflecting progressive putaminal involvement. This "eye" was found in all patients with MEGDEL syndrome during a specific age range, and has not been reported in other disorders, making it pathognomonic for MEDGEL and allowing diagnosis based on MRI findings.
Georg Thieme Verlag KG Stuttgart · New York.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
Enzyme replacement therapy (ERT) has been shown to improve outcome in classical infantile Pompe disease. The purpose of this study was to assess mortality, morbidity, and shortcomings of ERT in a larger cohort of patients treated outside clinical trials. To accomplish this, we retrospectively analyzed the data of all 23 subjects with classical infantile Pompe disease having started ERT in Germany between January 2003 and December 2010.
Ten patients (43%) deceased and four others (17%) became ventilator dependent. Seven infants (30.5%) made no motor progress at all, while seven (30.5%) achieved free sitting, and nine (39%) gained free walking. Besides all the seven patients (100%) attaining no improvement of motor functions, four out of the seven (57%) achieving to sit without support, and three out of the nine (33%) being able to walk independently, secondarily deteriorated, and died or became ventilator dependent. Sustained reduction of systolic function despite reversal of cardiac hypertrophy (n = 3), gastroesophageal reflux (n = 5), swallowing difficulties or failure to thrive (n = 11), recurrent pneumonias (n = 14), port system complications (n = 4), anesthesia-related incidents (n = 2), severe allergic reactions (n = 6), hearing loss (n = 3), and orthopedic deformities (n = 4) were problems frequently encountered.
Although this study has important shortcomings due to its retrospective nature and because important variables potentially influencing outcome were not available for a substantial amount of patients, these data suggest that classical infantile Pompe disease still remains a life-threatening condition associated with high morbidity and often dismal prognosis. Currently, a relevant number of patients do not benefit definitely from ERT.
[Show abstract][Hide abstract] ABSTRACT: In humans, lack of phenylalanine hydroxylase (Pah) activity results in phenylketonuria (PKU), which is associated with the development of severe mental retardation after birth. The underlying mechanisms, however, are poorly understood. Mutations of the Pah gene in Pah(enu2/)c57bl6 mice result in elevated levels of phenylalanine in serum similar to those in humans suffering from PKU. In our study, long-term potentiation (LTP) and paired-pulse facilitation (PPF), measured at CA3-CA1 Schaffer collateral synapses, were impaired in acute hippocampal slices of Pah(enu2/)c57bl6 mice. In addition, we found reduced expression of presynaptic proteins, such as synaptophysin and the synaptosomal-associated protein 25 (SNAP 25), and enhanced expression of postsynaptic marker proteins, such as synaptopodin and spinophilin. Stereological counting of spine synapses at the ultrastructural level revealed higher synaptic density in the hippocampus, commencing at 3 weeks and persisting up to 12 weeks after birth. Consistent effects were seen in response to phenylalanine treatment in cultures of dissociated hippocampal neurons. Most importantly, in the hippocampus of Pah(enu2/)c57bl6 mice we found a significant reduction in microglia activity. Reorganization of hippocampal circuitry after birth, namely synaptic pruning, relies on elimination of weak synapses by activated microglia in response to neuronal activity. Hence, our data strongly suggest that reduced microglial activity in response to impaired synaptic transmission affects physiological postnatal remodelling of synapses in the hippocampus and may trigger the development of mental retardation in PKU patients after birth.
Human Molecular Genetics 10/2014; 24(4). DOI:10.1093/hmg/ddu515 · 6.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
Hepatorenal tyrosinaemia (Tyr 1) is a rare inborn error of tyrosine metabolism. Without treatment, patients are at high risk of developing acute liver failure, renal dysfunction and in the long run hepatocellular carcinoma. The aim of our study was to collect cross-sectional data.Methods
Via questionnaires we collected retrospective data of 168 patients with Tyr 1 from 21 centres (Europe, Turkey and Israel) about diagnosis, treatment, monitoring and outcome. In a subsequent consensus workshop, we discussed data and clinical implications.ResultsEarly treatment by NTBC accompanied by diet is essential to prevent serious complications such as liver failure, hepatocellular carcinoma and renal disease. As patients may remain initially asymptomatic or develop uncharacteristic clinical symptoms in the first months of life newborn mass screening using succinylacetone (SA) as a screening parameter in dried blood is mandatory for early diagnosis. NTBC-treatment has to be combined with natural protein restriction supplemented with essential amino acids. NTBC dosage should be reduced to the minimal dose allowing metabolic control, once daily dosing may be an option in older children and adults in order to increase compliance. Metabolic control is judged by SA (below detection limit) in dried blood or urine, plasma tyrosine (<400 ¿M) and NTBC-levels in the therapeutic range (20¿40 ¿M). Side effects of NTBC are mild and often transient.Indications for liver transplantation are hepatocellular carcinoma or failure to respond to NTBC. Follow-up procedures should include liver and kidney function tests, tumor markers and imaging, ophthalmological examination, blood count, psychomotor and intelligence testing as well as therapeutic monitoring (SA, tyrosine, NTBC in blood).Conclusion
Based on the data from 21 centres treating 168 patients we were able to characterize current practice and clinical experience in Tyr 1. This information could form the basis for clinical practice recommendations, however further prospective data are required to underpin some of the recommendations.
[Show abstract][Hide abstract] ABSTRACT: Background:
As patients with different types of mucopolysaccharidosis (MPS) and mucolipidosis (ML) may present with overlapping clinical features - including coarse face, hepatosplenomegaly, bone dysplasia and claw-hand deformities, collectively also called 'MPS-like phenotype', enzymatic and/or molecular genetic analyses are indispensable for accurate diagnosis and applying specific therapy. In this prospective study, we screened patients with symptoms compatible with MPS for MPS I, II (males) and VI.
Dried blood spots/specimens (DBS) were collected from 200 patients with an MPS-like phenotype and analysed for activities of α-iduronidase (IDUA), iduronate-2-sulphatase (IDS), and arylsulphatase B (ARSB), the enzymes deficient in mucopolysaccharidosis (MPS) type I, II and VI, respectively. For the samples with pathologic enzyme activity, mutational analysis was carried out using the same DBS.
Based on enzymatic analysis of 200 DBS samples, a total of 45 (22.5%) showed low activity; 17 for MPS I (8.5%), 11 for MPS II (5.5%) and 9 for MPS VI (4.5%). Enzyme activities were suggestive for ML II/III in 8 (4.0%) cases. For 41 (91.1%) samples, DNA could be extracted from the filter paper. Mutations were identified in 11 (64.7%), 11 (100%), 9 (100%) and 5 (62.5%) patients putatively diagnosed biochemically with MPS I, II, VI, and ML II/III, respectively.
DBS enzymatic analysis can be used to diagnose MPS/ML. Initial results should be confirmed by a second enzyme assay and/or by molecular genetic testing. Given the advantages of DBS over other sample types in terms of ease of collection, storage and transportation, DBS are particularly useful for screening patients with an MPS-like phenotype in regions lacking specialised laboratories. In order to ascertain the diagnosis in a large number of cases, patients should be assessed in parallel for at least MPS I, II and VI.
[Show abstract][Hide abstract] ABSTRACT: Osteopetrosis is an inherited disorder of impaired bone resorption with the most commonly affected genes being CLCN7 and TCIRG1, encoding the Cl(-) /H(+) exchanger CLC-7 and the a3 subunit of the vacuolar H(+) -ATPase, respectively. We, and others have previously shown that the disease is frequently accompanied by osteomalacia, and that this additional pathology is also found in Tcirg1-deficient oc/oc mice. The remaining question was, whether osteoid enrichment is specifically associated with TCIRG1 inactivation, or whether CLCN7 mutations would also cause skeletal mineralization defects. Here we describe a complete osteologic assessment of one family carrying a novel mutation in CLCN7 (D145G), which impairs the activation and relaxation kinetics of the CLC-7 ion transporter. The two siblings carrying the mutation in the homozygous state displayed high bone mass, increased serum levels of bone formation markers, but no impairment of calcium homeostasis when compared to the other family members. Most importantly however, undecalcified processing of an iliac crest biopsy from one of the affected children clearly demonstrated a pathological increase of trabecular bone mass, but no signs of osteomalacia. Given the potential relevance of these findings we additionally performed undecalcified histology of iliac crest biopsies from seven additional cases with osteopetrosis caused by a mutation in TNFRSF11A (n = 1), CLCN7 (n = 3) or TCIRG1 (n = 3). Here we observed that all cases with TCIRG1-dependent osteopetrosis displayed severe osteoid accumulation and decreased calcium content within the mineralized matrix. In contrast, there was no detectable bone mineralization defect in the cases with TNFRSF11A- or CLCN7-dependent osteopetrosis. Taken together, our analysis demonstrates that CLCN7 and TCIRG1 mutations differentially affect bone matrix mineralization, and that there is a need to modify the current classification of osteopetrosis.
Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 04/2014; 29(4). DOI:10.1002/jbmr.2100 · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Combined D,L-2-hydroxyglutaric aciduria (DL-2HGA; OMIM #615182) is a rare neurometabolic disorder clinically characterized by muscular hypotonia, severe neurodevelopmental dysfunction, and intractable seizures associated with respiratory distress. Biochemically, DL-2HGA patients excrete increased amounts of D- and L-2-hydroxyglutarate (D2HG and L2HG, respectively), with predominance of D2HG, and α-ketoglutarate, and show a decrease in urinary citrate. Impaired function of the mitochondrial citrate carrier (CIC) due to pathogenic mutations within the SLC25A1 gene has been identified as the underlying molecular cause of the disease. CIC mediates efflux of the mitochondrial tricarboxylic acid (TCA) cycle intermediates citrate and isocitrate in exchange for cytosolic malate. Thus, depletion of cytosolic citrate as well as accumulation of citrate inside mitochondria have been considered to play a role in the pathophysiology of DL-2HGA. Here, we report for the first time on a patient with a genetically confirmed diagnosis of DL-2HGA and treatment with either malate or citrate. During malate treatment, urinary malate concentration increased, but beyond that, neither biochemical nor clinical alterations were observed. In contrast, treatment with citrate led to an increased urinary excretion of TCA cycle intermediates malate and succinate, and by trend to an increased concentration of urinary citrate. Furthermore, excretion of D2HG and L2HG was reduced during citrate treatment. Clinically, the patient showed stabilization with regard to frequency and severity of seizures. Treating DL-2HGA with citrate should be considered in other DL-2HGA patients, and its effects should be studied systematically.
[Show abstract][Hide abstract] ABSTRACT: Deficiency of apoprotein A-V (apoA-V) can cause hypertriglyceridemia. In an 11 months old boy presenting with a severe hypertriglyceridemia, a formerly unknown 24 nucleotide deletion in exon 2 of the APOA5 gene was detected. The homozygous mutation results in an eight amino acid loss in the signal peptide sequence (c.16_39del; p.Ala6_Ala13del). Screening of control persons proved that this deletion is a rare mutation. Hypertriglyceridemia in the patient was only found at the time when he was breast fed, while after weaning, triglyceride levels were close to normal. Under both dietary conditions, apoA-V protein was undetectable in plasma while post-heparin plasma lipoprotein lipase activity was normal.
Expression analysis of normal and mutated protein by Western blot and immunofluorescence in apoA-V deficient primary hepatocytes revealed that, due to changes in the signal peptide, mutated apoA-V was intracellularly missorted to lipid droplets and not secreted. Wild type apoA-V, instead, was not targeted to lipid droplets but transported via endosomal compartments to the plasma membrane for secretion.
It is concluded that the c.16_39del mutation in the APOA5 gene leads to hepatic missorting and impaired secretion, which consequently results in undetectable apoA-V plasma levels. The absence of apoA-V in plasma leads under conditions of fat-rich diets to severe chylomicronemia, suggestive for a modulatory role of apoA-V for lipoprotein lipase mediated intravascular triglyceride lipolysis.
[Show abstract][Hide abstract] ABSTRACT: Defective nectin-1 and -4 have been implicated in ectodermal dysplasia (ED) syndromes with variably associated features including orofacial and limb defects. In particular, nectin-1 mutations cause cleft lip/palate ED (CLPED1; OMIM#225060), while defective nectin-4 is associated with ED-syndactyly syndrome (EDSS1; OMIM#613573). Although the broad phenotypic overlap suggests a common mode of action of nectin-1 and -4, little is known about the pathogenic mechanisms involved. We report the identification of a previously undescribed nectin-4 homozygous p.Val242Met missense mutation in a patient with EDSS1. We used patient skin biopsy and primary keratinocytes, as well as nectin-4 ectopic expression in epithelial cell lines, to characterize functional consequences of p.Val242Met and p.Thr185Met mutations, the latter previously identified in compound heterozygosity with a truncating mutation. We show that nectin-4 altered expression perturbs nectin-1 clustering at keratinocyte contact sites and delays, but does not impede, cell-cell aggregation and cadherin recruitment at adherens junctions (AJ). Moreover, trans-interaction of nectin-1 and -4 induces the activation of Rac1, a member of the Rho family of small GTPases, and regulates E-cadherin-mediated cell-cell adhesion. These data outline a synergistic action of nectin-1 and -4 in the early steps of AJ formation and implicate this interaction in modulating Rac1-signaling pathway.Journal of Investigative Dermatology accepted article preview online, 27 February 2014; doi:10.1038/jid.2014.119.
[Show abstract][Hide abstract] ABSTRACT: Mucolipidosis type II (MLII) is a severe multi-systemic genetic disorder caused by missorting of lysosomal proteins and the subsequent lysosomal storage of undegraded macromolecules. Although affected children develop disabling skeletal abnormalities, their pathogenesis is not understood. Here we report that MLII knock-in mice, recapitulating the human storage disease, are runted with accompanying growth plate widening, low trabecular bone mass and cortical porosity. Intralysosomal deficiency of numerous acid hydrolases results in accumulation of storage material in chondrocytes and osteoblasts, and impaired bone formation. In osteoclasts, no morphological or functional abnormalities are detected whereas osteoclastogenesis is dramatically increased in MLII mice. The high number of osteoclasts in MLII is associated with enhanced osteoblastic expression of the pro-osteoclastogenic cytokine interleukin-6, and pharmacological inhibition of bone resorption prevented the osteoporotic phenotype of MLII mice. Our findings show that progressive bone loss in MLII is due to the presence of dysfunctional osteoblasts combined with excessive osteoclastogenesis. They further underscore the importance of a deep skeletal phenotyping approach for other lysosomal diseases in which bone loss is a prominent feature.
EMBO Molecular Medicine 12/2013; 5(12). DOI:10.1002/emmm.201302979 · 8.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
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.
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.
European Journal of Pediatrics 07/2013; 172(9). DOI:10.1007/s00431-013-2084-6 · 1.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Urea cycle disorders (UCDs) are inherited disorders of ammonia detoxification often regarded as mainly of relevance to pediatricians. Based on an increasing number of case studies it has become obvious that a significant number of UCD patients are affected by their disease in a non-classical way: presenting outside the newborn period, following a mild course, presenting with unusual clinical features, or asymptomatic patients with only biochemical signs of a UCD. These patients are surviving into adolescence and adulthood, rendering this group of diseases clinically relevant to adult physicians as well as pediatricians. In preparation for an international workshop we collected data on all patients with non-classical UCDs treated by the participants in 20 European metabolic centres. Information was collected on a cohort of 208 patients 50% of which were ≥ 16 years old. The largest subgroup (121 patients) had X-linked ornithine transcarbamylase deficiency (OTCD) of whom 83 were female and 29% of these were asymptomatic. In index patients, there was a mean delay from first symptoms to diagnosis of 1.6 years. Cognitive impairment was present in 36% of all patients including female OTCD patients (in 31%) and those 41 patients identified presymptomatically following positive newborn screening (in 12%). In conclusion, UCD patients with non-classical clinical presentations require the interest and care of adult physicians and have a high risk of neurological complications. To improve the outcome of UCDs, a greater awareness by health professionals of the importance of hyperammonemia and UCDs, and ultimately avoidance of the still long delay to correctly diagnose the patients, is crucial.
[Show abstract][Hide abstract] ABSTRACT: The Krebs cycle is of fundamental importance for the generation of the energetic and molecular needs of both prokaryotic and eukaryotic cells. Both enantiomers of metabolite 2-hydroxyglutarate are directly linked to this pivotal biochemical pathway and are found elevated not only in several cancers, but also in different variants of the neurometabolic disease 2-hydroxyglutaric aciduria. Recently we showed that cancer-associated IDH2 germline mutations cause one variant of 2-hydroxyglutaric aciduria. Complementary to these findings, we now report recessive mutations in SLC25A1, the mitochondrial citrate carrier, in 12 out of 12 individuals with combined D-2- and L-2-hydroxyglutaric aciduria. Impaired mitochondrial citrate efflux, demonstrated by stable isotope labeling experiments and the absence of SLC25A1 in fibroblasts harboring certain mutations, suggest that SLC25A1 deficiency is pathogenic. Our results identify defects in SLC25A1 as a cause of combined D-2- and L-2-hydroxyglutaric aciduria.
The American Journal of Human Genetics 04/2013; 92(4):627-31. DOI:10.1016/j.ajhg.2013.03.009 · 10.93 Impact Factor