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Wahrend bis vor wenigen Jahren nur eine begrenzte Auswahl an digitalen Moglichkeiten zur genetischen Diagnostik zur Verfugung stand, kann heute zur Diagnosestellung auf eine Vielzahl von digitalen Datenbanken und genetischen Testsystemen zuruckgegriffen werden. Damit stieg auch die Zahl der genetischen Zuordnungen – abgesehen von einer immer groser werdenden Zahl von Genen, die mit Krankheitsbildern in Verbindung gebracht werden. Im Folgenden werden anhand eines komplexen neuropadiatrischen Krankheitsbildes die schrittweise Stufendiagnostik vorgestellt, die zur Diagnosestellung fuhrte, sowie weitere digitale Systeme, die aktuell fur verschiedene Fragestellungen nutzbar sind.

Spinal muscular atrophy is an autosomal-recessive neuromuscular disorder, causing progressive proximal weakness and atrophy of the voluntary muscles. More than 96% of the spinal muscular atrophy patients show a homozygous absence of exons 7 and 8, or exon 7 only, in SMN1, the telomeric copy of the SMN gene. We report a young male patient with neurogenic symptoms and sparse muscle fiber atrophy, suggestive of a mild form of type III spinal muscular atrophy. He was found to be a carrier of intragenic mutations in both copies of the SMN gene, exhibiting a homozygous duplication of exons 7 and 8 in SMN1 and a homozygous deletion of exon 8 as well as a heterozygous deletion of exon 7 in SMN2. However, an intact full-length SMN1 complementary deoxyribonucleic acid was identified, and SMN protein levels in a muscle specimen were identical to that of a healthy control, formally excluding the diagnosis of spinal muscular atrophy III.

Department of Neurology & Neurosurgery, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands Department of Pediatrics, Pediatric Pathology Unit, Hacettepe University, Ankara, Turkey Department of Clinical Neurophysiology, Great Ormond Street Hospital for Sick Children NHS Trust, WC1N 3JH London, United Kingdom Department of Pediatric Neurology, Charite University Medical Center, Augustenburger Platz 1, 13353 Berlin, Germany

Distal spinal muscular atrophy type 1 (DSMA1) is an autosomal recessive disease that is clinically characterized by distal limb weakness and respiratory distress. In this disease, the degeneration of alpha-motoneurons is caused by mutations in the immunoglobulin mu-binding protein 2 (IGHMBP2). This protein has been implicated in DNA replication, pre-mRNA splicing and transcription, but its precise function in all these processes has remained elusive. We have purified catalytically active recombinant IGHMBP2, which has enabled us to assess its enzymatic properties and to identify its cellular targets. Our data reveal that IGHMBP2 is an ATP-dependent 5' --> 3' helicase, which unwinds RNA and DNA duplices in vitro. Importantly, this helicase localizes predominantly to the cytoplasm of neuronal and non-neuronal cells and associates with ribosomes. DSMA1-causing amino acid substitutions in IGHMBP2 do not affect ribosome binding yet severely impair ATPase and helicase activity. We propose that IGHMBP2 is functionally linked to translation, and that mutations in its helicase domain interfere with this function in DSMA1 patients.

Distal spinal muscular atrophy type 1 (DSMA1) is caused by mutations in the immunoglobulin mu-binding protein 2 (IGHMBP2) gene. Patients with DSMA1 present between 6 weeks and 6 months of age with progressive muscle weakness and respiratory failure due to diaphragmatic palsy. Contrary to this "classic" infantile disease, we have previously described a DSMA1 patient with juvenile disease onset. In this paper, we present (1) a second juvenile case and (2) the first study of DSMA1 on protein level in patients with infantile (n = 3) as well as juvenile (n = 2) disease onset observing elevated residual steady-state IGHMBP2 protein levels in the patients with late onset DSMA1 as compared to those with classic DSMA1. Mutation screening in IGHMBP2 revealed two patients compound heterozygous for a novel missense mutation (c.1478C-->T; p.T493I) and another previously described mutation. In lymphoblastoid cells of both patients, steady-state IGHMBP2 protein levels were reduced. In comparison to wild-type IGHMBP2, the p.T493I variant protein had an increased tendency to aggregate and spontaneously degrade in vitro. We verified a change in the physicochemical properties of the p.T493I variant which may explain the pathogenicity of this mutation. Our data further suggest that the age of onset of DSMA1 is variable, and we discuss the effect of residual IGHMBP2 protein levels on the clinical course and the severity of the disease.

Autosomal recessive spinal muscular atrophy with respiratory distress (SMARD) is a heterogeneous disorder. Mutations in the immunoglobulin micro-binding protein gene (IGHMBP2) lead to SMARD1, but clinical criteria that delineate SMARD1 from other SMARD syndromes are not well established. Here we present a retrospective clinical and genetic study to determine the criteria that would predict the presence or absence of IGHMBP2 mutations. From 141 patients with respiratory distress and a spinal muscular atrophy phenotype we recorded the clinical features through a questionnaire and sequenced the entire coding region of IGHMBP2. In 47 (33%) patients we identified IGHMBP2 mutations, 14 of which were not described before. Clinical features and combinations thereof associated with the presence of IGHMBP2 mutations were discovered through hierarchical cluster analysis. This method detects common traits not evident at first sight by grouping items according to their similarity. The combination of "manifestation of respiratory failure between 6 weeks and 6 months" AND ("presence of diaphragmatic eventration" OR "preterm birth") predicted the presence of IGHMBP2 mutations with 98% sensitivity and 92% specificity. Non-SMARD1 patients fell into two different symptom clusters, mainly separated by the age at respiratory failure and the presence of multiple congenital contractures. The 14 novel IGHMBP2 mutations comprised missense, frameshift, splice-site, and nonsense mutations. All missense mutations altered conserved residues within or adjacent to the putative DNA helicase domain. The c.1235+3A>G splice-site mutation did not entirely suppress correct splicing and we found a residual wild-type IGHMBP2 mRNA steady-state level of 24.4+/-6.9%, which was, however, not sufficient to avert SMARD1 in this patient.

Objective: To identify the cause of sensorimotor neuropathy in a cohort of patients with genetically unsolved neuropathies (57 families with a total of 74 members) in whom hitherto known disease genes had been excluded. Methods: We used autozygosity mapping or haplotype analysis to delineate potential disease loci in informative families. For mutation detection, we used either whole-exome sequencing or Sanger sequencing of positional candidates. Subsequently, a larger cohort was specifically screened for IGHMBP2 mutations. The pathogenicity of a splice-site mutation was verified in cultured patient skin fibroblasts on the messenger RNA level and by Western blot. Results: We report on 5 patients with neuropathy from 3 families who carried truncating mutations in IGHMBP2 . Contrary to the “classic” phenotype, they did not manifest with respiratory distress, but with progressive sensorimotor neuropathy. Only one patient required nocturnal mask ventilation, while 4 others maintained normal respiratory function by the age of 14, 18, 22, and 37 years. Three patients were still able to walk independently. All patients had a predominantly axonal sensorimotor neuropathy with subsequent muscle atrophy, but without obvious sensory symptoms. Two patients had signs of autonomic neuropathy. Conclusions: Mutations in IGHMBP2 should be considered in the molecular genetic workup of patients with hereditary sensorimotor neuropathies, even in the absence of respiratory symptoms.

Pain perception has evolved as a warning mechanism to alert organisms to tissue damage and dangerous environments. In humans, however, undesirable, excessive or chronic pain is a common and major societal burden for which available medical treatments are currently suboptimal. New therapeutic options have recently been derived from studies of individuals with congenital insensitivity to pain (CIP). Here we identified 10 different homozygous mutations in PRDM12 (encoding PRDI-BF1 and RIZ homology domain-containing protein 12) in subjects with CIP from 11 families. Prdm proteins are a family of epigenetic regulators that control neural specification and neurogenesis. We determined that Prdm12 is expressed in nociceptors and their progenitors and participates in the development of sensory neurons in Xenopus embryos. Moreover, CIP-associated mutants abrogate the histone-modifying potential associated with wild-type Prdm12. Prdm12 emerges as a key factor in the orchestration of sensory neurogenesis and may hold promise as a target for new pain therapeutics. © 2015 Nature America, Inc. All rights reserved.

Purpose To evaluate clinical outcomes and complications after Descemet membrane endothelial keratoplasty (DMEK) in a child. Methods A 12-year-old boy with Kearns-Sayre syndrome (chronic progressive external ophthalmoplegia, cardiac conduction block, and pigmentary retinal degeneration) and corneal endothelial dysfunction was successfully treated with DMEK. Corneal transparency, central corneal thickness (CCT), endothelial cell density (ECD), visual outcomes, and complication rates were measured during the follow-up of 6 months. Results Best spectacle-corrected visual acuity (BSCVA) improved from counting fingers at 4 feet preoperatively to 20/100, 1 week after surgery. The ECD of the graft was 2595 cells per square millimeter. The CCT diminished from 837 μm preoperatively to 735 μm 1 week after surgery. Six months postoperatively, the BSCVA was still 20/100, and the cornea remained clear and compact. The ECD was 2341 cells per square millimeter and CCT was almost normal with 583 μm. No postoperative complications were observed. Fundus examination showed atypical pigmentary retinal degeneration with arterial narrowing. Electroretinography with full-field flash stimulation showed bilaterally severe retinal dysfunction with absent photopic and scotopic amplitudes explaining the reduced BSCVA. Conclusions Although DMEK has been used in adult populations, we are unaware of previous reports of DMEK in a child. DMEK should be considered as a feasible technique in pediatric patients with endothelial dysfunction.

Using a combination of exome sequencing and linkage analysis, we investigated an English family with two affected siblings in their 40s with recessive Charcot-Marie Tooth disease type 2 (CMT2). Compound heterozygous mutations in the immunoglobulin-helicase-μ-binding protein 2 (IGHMBP2) gene were identified. Further sequencing revealed a total of 11 CMT2 families with recessively inherited IGHMBP2 gene mutations. IGHMBP2 mutations usually lead to spinal muscular atrophy with respiratory distress type 1 (SMARD1), where most infants die before 1 year of age. The individuals with CMT2 described here, have slowly progressive weakness, wasting and sensory loss, with an axonal neuropathy typical of CMT2, but no significant respiratory compromise. Segregating IGHMBP2 mutations in CMT2 were mainly loss-of-function nonsense in the 5′ region of the gene in combination with a truncating frameshift, missense, or homozygous frameshift mutations in the last exon. Mutations in CMT2 were predicted to be less aggressive as compared to those in SMARD1, and fibroblast and lymphoblast studies indicate that the IGHMBP2 protein levels are significantly higher in CMT2 than SMARD1, but lower than controls, suggesting that the clinical phenotype differences are related to the IGHMBP2 protein levels.

Angelman syndrome is a neurodevelopmental disorder characterized by mental retardation, severe speech disorder, facial dysmorphism, secondary microcephaly, ataxia, seizures, and abnormal behaviors such as easily provoked laughter. It is most frequently caused by a de novo maternal deletion of chromosome 15q11-q13 (about 70-90%), but can also be caused by paternal uniparental disomy of chromosome 15q11-q13 (3-7%), an imprinting defect (2-4%) or in mutations in the ubiquitin protein ligase E3A gene UBE3A mostly leading to frame shift mutation. In addition, for patients with overlapping clinical features (Angelman-like syndrome), mutations in methyl-CpG binding protein 2 gene MECP2 and cyclin-dependent kinase-like 5 gene CDKL5 as well as a microdeletion of 2q23.1 including the methyl-CpG binding domain protein 5 gene MBD5 have been described. Here, we describe a patient who carries a de novo 5Mb-deletion of chromosome 15q11.2-q13.1 known to be associated with Angelman syndrome and a further, maternally inherited deletion 2q21.3 (~364kb) of unknown significance. In addition to classic features of Angelman syndrome, she presented with severe infections in the first year of life, a symptom that has not been described in patients with Angelman syndrome. The 15q11.2-q13.1 deletion contains genes critical for Prader-Willi syndrome, the Angelman syndrome causing genes UBE3A and ATP10A/C, and several non-imprinted genes: GABRB3 and GABRA5 (both encoding subunits of GABA A receptor), GOLGA6L2, HERC2 and OCA2 (associated with oculocutaneous albinism II). The deletion 2q21.3 includes exons of the genes RAB3GAP1 (associated with Warburg Micro syndrome) and ZRANB3 (not disease-associated). Despite the normal phenotype of the mother, the relevance of the 2q21.3 microdeletion for the phenotype of the patient cannot be excluded, and further case reports will need to address this point.

Background: Only scarce information is available on the long-term outcome and the natural course of children with infantile spinal muscular atrophy with respiratory distress type 1 (SMARD1) due to mutations in the IGHMBP2 gene. Objective: To describe the natural disease course, to systematically quantify the residual capacities of children with SMARD1 who survive on permanent mechanical respiration, and to identify markers predicting the disease outcome at the time of manifestation. Methods: We conducted a longitudinal study of 11 infantile SMARD1 patients over a mean observational period of 7.8 (SD 3.2) years. Disease-specific features were continuously assessed by using a semiquantitative scoring system. Additionally, we analyzed the residual enzymatic activity of 6 IGHMBP2 mutants in our patients. Results: After an initial rapid decline of the clinical score until the age of 2 years, residual capabilities reached a plateau or even improved. The overall clinical outcome was markedly heterogeneous, but clinical scores at the age of 3 months showed a positive linear correlation with the clinical outcome at 1 year and at 4 years of age. If expressed in an in vitro recombinant system, mutations of patients with more favorable outcomes retained residual enzymatic activity. Conclusions: Despite their severe disabilities and symptoms, most SMARD1 patients are well integrated into their home environment and two thirds of them are able to attend kindergarten or school. This information will help to counsel parents at the time of disease manifestation.

Autosomal recessive spinal muscular atrophy with respiratory distress type 1 (SMARD1), recently referred to as distal spinal muscular atrophy 1 (DSMA1; MIM#604320) and also known as distal hereditary motor neuropathy type 6 (dHMN6 or HMN6), results from mutations in the IGHMBP2 gene on chromosome 11q13.3 encoding the immunoglobulin µ-binding protein 2. In contrast to the infantile spinal muscular atrophy type 1 (SMA1; Werdnig-Hoffmann disease) with weakness predominantly of proximal muscles and bell-shaped thorax deformities due to intercostal muscle atrophy, infants with distal spinal muscular atrophy 1 usually present with distal muscle weakness, foot deformities, and sudden respiratory failure due to diaphragmatic paralysis that often requires urgent intubation. In this article, the authors review the clinical, neuropathological, and genetic aspects of distal spinal muscular atrophy 1 and discuss differential diagnoses.

Nat. Genet. 47 803–808 (2015); published online 25 May 2015; corrected after print 8 July 2015 In the version of this article initially published, there was an error with the affiliations for author Roman Chrast. His correct affiliations are: Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland; Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; and Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.

Motor neuron degeneration is the predominant pathological feature of spinal muscular atrophy (SMA). In patients with severe forms of the disease, additional sensory abnormalities have been reported. However, it is not clear whether the loss of sensory neurons is a common feature in severe forms of the disease, how many neurons are lost and how loss of sensory neurons compares with motor neuron degeneration. We have analysed dorsal root ganglionic sensory neurons in Smn-/-;SMN2 mice, a model of type I SMA. In contrast to lumbar motor neurons, no loss of sensory neurons in the L5 dorsal root ganglia is found at post-natal days 3-5 when these mice are severely paralyzed and die from motor defects. Survival of cultured sensory neurons in the presence of NGF and other neurotrophic factors is not reduced in comparison to wild-type controls. However, isolated sensory neurons have shorter neurites and smaller growth cones, and beta-actin protein and beta-actin mRNA are reduced in sensory neurite terminals. In footpads of Smn-deficient mouse embryos, sensory nerve terminals are smaller, suggesting that Smn deficiency reduces neurite outgrowth during embryogenesis. These data indicate that pathological alterations in severe forms of SMA are not restricted to motor neurons, but the defects in the sensory neurons are milder than those in the motor neurons.