Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is the most common defect of mitochondrial β-oxidation of long-chain fatty acids. However, the unambiguous diagnosis of true VLCADD patients may be challenging, and a high rate of false positive individuals identified by newborn screening undergo confirmation diagnostics. In this study, we show the outcome of enzyme testing in lymphocytes as a confirmatory tool in newborns identified by screening, and the correlation with molecular sequencing of the ACADVL gene. From April 2013 to March 2017, in 403 individuals with characteristic acylcarnitine profiles indicative of VLCADD, palmitoyl-CoA oxidation was measured followed by molecular genetic analysis in most of the patients with residual activity (RA) <50%. In almost 50% of the samples (209/403) the RA was >50%, one-third of the individuals (125/403) displayed a RA of 30-50% and 69/403 individuals showed a residual activity of 0-30%. Sequencing of the ACADVL gene revealed that all individuals with activities below 24% were true VLCADD patients, individuals with residual activities between 24 and 27% carried either one or two mutations. Twenty new mutations could be identified and functionally classified based on their effect on enzyme function. Finally, we observed an up-regulation of MCAD-activity in many patients. However, this did not correlate with the degree of VLCAD RA. Although the likely clinical phenotype cannot be fully foreseen by genetic and functional tests as it depends on many factors, our data demonstrate the strength of this functional enzyme test in lymphocytes as a quick and reliable method for confirmation diagnostics of VLCADD.

Vertebral, Cardiac, Renal and Limb Defect Syndrome (VCRL), is a very rare congenital malformation syndrome. Pathogenic variants in HAAO (3-Hydroxyanthranilate 3,4-dioxygenase), NADSYN1 (NAD+ Synthetase-1) and KYNU (Kynureninase) have been identified in a handful of affected individuals. All three genes encode for enzymes essential for the NAD+ de novo synthesis pathway. Using Trio-Exome analysis and CGH array analysis in combination with long range PCR, we have identified a novel homozygous copy number variant (CNV) encompassing exon 5 of KYNU in an individual presenting with overlapping features of VCRL and Catel–Manzke Syndrome. Interestingly, only the mother, not the father carried the small deletion in a heterozygous state. High-resolution SNP array analysis subsequently delineated a maternal isodisomy of chromosome 2 (UPD2). Increased xanthurenic acid excretion in the urine confirmed the genetic diagnosis. Our findings confirm the clinical, genetic and metabolic phenotype of VCRL1, adding a novel functionally tested disease allele. We also describe the first patient with NAD+ deficiency disorder resulting from a UPD. Furthermore, we provide a comprehensive review of the current literature covering the genetic basis and pathomechanisms for VCRL and Catel–Manzke Syndrome, including possible phenotype/genotype correlations as well as genetic causes of hypoplastic left heart syndrome.

Schmid-type metaphyseal chondrodysplasia (MIM 156500) is an uncommon autosomal dominant skeletal dysplasia caused by heterozygous mutations in the COL10A1 gene (MIM 120110) encoding the α1(X) chains of type X collagen. We report an 8-year-old girl with waddling gait, short stature, mild dorsal scoliosis, coxa vara, short lower limbs, bowing of the femurs, genu varum, and metaphyseal fraying and splaying, who is a carrier of a novel heterozygous 2-bp (c.1894_1895dupTA; p.Leu633Thrfs*45) duplication in exon 3 of the COL10A1 gene.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common defect of mitochondrial β-oxidation. Confirmation diagnostics after newborn screening (NBS) can be performed either by enzyme testing and/or by sequencing of the ACADM gene. Here, we report the results from enzyme testing in lymphocytes with gene variants from molecular analysis of the ACADM gene and with the initial acylcarnitine concentrations in the NBS sample. From April 2013 to August 2019, in 388 individuals with characteristic acylcarnitine profiles suggestive of MCADD the octanoyl-CoA-oxidation was measured in lymphocytes. In those individuals with residual activities <50%, molecular genetic analysis of the ACADM gene was performed. In 50% of the samples (195/388), MCADD with a residual activity ranging from 0% to 30% was confirmed. Forty-five percent of the samples (172/388) showed a residual activity >35% excluding MCADD. In the remaining 21 individuals, Abbreviations: MCAD, medium-chain acyl-CoA dehydrogenase; MCADD, medium-chain acyl-CoA dehydrogenase deficiency; NBS, newborn screening; VLCAD, very long-chain acyl-CoA dehydrogenase.

Vascular malformations are most often caused by somatic mutations of the PI3K/mTOR and the RAS signaling pathways, which can be identified in the affected tissue. Venous malformations commonly harbor PIK3CA and TEK mutations, whereas arteriovenous malformations are usually caused by BRAF, RAS, or MAP2K1 mutations. Correct identification of the underlying mutation is of increasing importance, since targeted treatments are becoming more and more relevant, especially in patients with extensive vascular malformations. However, variants of unknown significance are often identified and their pathogenicity and response to targeted therapy cannot be precisely predicted. Here we show, that zebrafish embryos can be used to rapidly assess the pathogenicity of novel variants of unknown significance in TEK, encoding for the receptor TIE2, present on endothelial cells of venous malformations. Endothelium-specific overexpression of TEK mutations leads to robust induction of venous malformations whereas MAP2K1 mutations cause arteriovenous malformations in our zebrafish model. TEK mutations are often found as double mutations in cis; using our model, we show that double mutations have an additive effect in inducing venous malformations compared to the respective single variants. The clinically established mTOR-inhibitor sirolimus (rapamycin) efficiently abrogates the development of venous malformations in this zebrafish model. In summary, endothelium-specific overexpression of patient-derived TEK variants in the zebrafish model allows assessment of their pathogenic significance as well as testing of candidate drugs in a personalized and mutation-specific approach.

Spondylometaphyseal dysplasia Algerian type (MIM no.: 184253) is an uncommon autosomal dominant skeletal dysplasia caused by heterozygous mutations in the COL2A1 gene (MIM no.: 120140). In this case based review, we reported a 5-year-old boy with short stature, severe dorsolumbar scoliosis, lumbar hyperlordosis, short trunk, and severe genu valgum. Radiological examination showed platyspondyly, irregular metaphyseal radiolucencies intermingled with radiodensities, and corner fractures. The patient has a c.3275G > A; p.Gly1092Asp mutation in exon 47 of the COL2A1 gene and a variant of unknown significance in c.1366–13C > A in intron 21. This latter sequence variant could partially or completely disrupt the natural splice acceptor site of intron 21/exon 22 in the COL2A1 gene leading to a potential modification of the phenotypic severity.

Hypomethylation of H19 and IGF2 can cause Silver–Russell syndrome (SRS), a clinically and genetically heterogeneous condition characterized by intrauterine growth restriction, poor postnatal growth, relative macrocephaly, craniofacial abnormalities, body asymmetry, hypoglycemia and feeding difficulties. Isolated hypomethylation of IGF2 has been reported in single cases of SRS as well. Here, we report on a 19-month-old patient who presented with two episodes of hypoglycemic seizures. No intrauterine growth restriction was observed, the patient did not present with SRS-typical facial features, and postnatal growth in the first months of life was along the lower normal percentiles. Exome sequencing did not reveal any likely pathogenic variants explaining the phenotype; however, hypomethylation studies revealed isolated hypomethylation of IGF2, while the methylation of H19 appeared normal. Hypoglycemia responded well to growth hormone therapy, and the boy showed good catch-up growth. Our case demonstrates that SRS and isolated IGF2 hypomethylation should be considered early in the diagnosis of recurrent hypoglycemia in childhood, especially in combination with small gestational age and poor growth.

Ein 10 Wochen alter weiblicher Säugling wurde in unserer Ambulanz vorgestellt. Den Eltern des Mädchens waren sofort nach Geburt beidseits weite Pupillen bei fehlender Iris und ein weißer zentraler Fleck auf beiden Hornhäuten aufgefallen. Es bestand zu dem Zeitpunkt kein Nystagmus. Systemische Erkrankungen waren nicht bekannt. Eine sonographische Untersuchung der Bauchorgane ergab einen Normalbefund. Abb. 1 8 Stammbaum der Patientin mit den von Aniridie betroffenen Familienmitglieder (hier in schwarz hervorgehoben) Abb. 2 8 Vorderabschnittsfotografie während der Untersuchung unter Allgemeinanästhesie. a Rechtes Auge, b linkes Auge