S. Lane Rutledge

Clinically relevant single gene or intragenic deletions encompassing critical neurodevelopmental genes in patients with developmental delay, mental retardation, and/or autism spectrum disorders.

Recent studies suggest that copy number variations (CNVs) encompassing several genes involved in neurodevelopmental pathways are associated with a variety of neuropsychiatric phenotypes, including developmental delay (DD), mental retardation (MR), and autism spectrum disorders (ASDs). Here we present eight patients in a cohort of ∼1,200 patients referred for clinical array CGH testing for various neurodevelopmental phenotypes, who were identified to carry small (<1.0 Mb with the majority <500 kb) either total gene or intragenic deletions encompassing critical synaptic and other neurodevelopmental genes. The presentations of these patients included variable degrees of DD, speech problems, learning disabilities, MR, autistic‐like features, and mild non‐specific dysmorphic features. These genes belong to four functional categories, including neuronal transcription factor genes (NFIA at 1p31.3, MEF2C at 5q14.3, and CAMAT1 at 1p36.23p36.31), neuron‐specific splicing factor genes (RBFOX1 at 16p13.2p13.3), genes involved in synapse formation and maintenance (CNTNAP2 at 7q35 and LRFN5 at 14q21.2), and genes involved in neurotransmission (CHRNA7 at 15q13.3 and IL1RAPL1 at Xp21.2p21.3). Our report expands the list of neurodevelopmental genes deleted in various neurobehavioral phenotypes, expands the phenotypes caused by haploinsufficiency of previously reported critical neurodevelopmental genes, and elucidates the clinical relevance and need for careful clinical interpretation of some small CNVs <500 kb. This report also suggests that small clinically relevant deletions encompassing critical synaptic and other neurodevelopmental genes can present clinically with various neurobehavioral phenotypes, which implies the existence of overlapping neuronal pathways in the pathogenesis of these phenotypes.

Neonatal hemodialysis: effective therapy for the encephalopathy of inborn errors of metabolism.

Maple syrup urine disease and argininosuccinate synthetase deficiency are two of many inborn errors of metabolism that may result in neonatal encephalopathy. Early treatment is designed to suppress endogenous proteolysis and amino acid catabolism with the infusion of glucose, and to remove presumed toxic metabolites. The latter goal has been accomplished with exchange transfusion, 13 peritoneal dialysis, 24 and hemodialysis. 2, 3 We present the cases of two neonates, one with M S U D and the other with argininosuccinate synthetase deficiency. The infants were treated with hemodialysis, during which the clearances of amino acids and ammonium were measured. We examined the hypothesis that hemodialysis is more effective then peritoneal dialysis or exchange transfusion in removing putative toxic metabolites,

Identification of novel mutations in the SLC25A15 gene in hyperornithinemia‐hyperammonemia‐homocitrullinuria (HHH) syndrome: A clinical, molecular, and functional study

Hyperornithinemia‐hyperammonemia‐homocitrullinuria (HHH) syndrome is an autosomal recessive disorder of the urea cycle. With the exception of the French‐Canadian founder effect, no common mutation has been detected in other populations. In this study, we collected 16 additional HHH cases and expanded the spectrum of SLC25A15/ORC1 mutations. Eleven novel mutations were identified including six new missense and one microrearrangement. We also measured the transport properties of the recombinant purified proteins in reconstituted liposomes for four new and two previously reported missense mutations and proved that the transport activities of these mutant forms of ORC1 were reduced as compared with the wild‐type protein; residual activity ranged between 4% and 19%. Furthermore, we designed three‐dimensional (3D)‐modeling of mutant ORC1 proteins. While modeling the changes in silico allowed us to obtain new information on the pathomechanisms underlying HHH syndrome, we found no clear‐cut genotype–phenotype correlations. Although patient metabolic alterations responded well to low‐protein therapy, predictions concerning the long‐term evolution of HHH syndrome remain uncertain. The preference for a hepatic rather than a neurological presentation at onset also continues, largely, to elude us. Neither modifications in oxidative metabolism‐related energy, such as those expected in different mtDNA haplogroups, nor sequence variants in SLC25A2/ORC2 seem to be crucial. Other factors, including protein stability and function, and ORC1‐ORC2 structural interactions should be further investigated. Hum Mutat 0, 1–8, 2009.

Tubulointerstitial nephritis in methylmalonic acidemia

We report two patients with methylmalonic acidemia (MMA) in whom renal biopsy demonstrated interstitial nephritis, bringing the total of such reported cases to four. In addition, hypertension, observed in one of our patients, has not been previously reported as the presentation of renal disease in MMA. The etiology of interstitial nephritis in MMA did not appear to be due to urate nephropathy. To date, 15 patients with MMA have been reported with renal complications, including chronic renal failure, making it imperative that children with MMA have their renal status evaluated.

Rasmussen syndrome and long-term response to gamma globulin.

Rasmussen syndrome (RS) is a severe and progressive focal epilepsy of unknown etiology that leads to deterioration of motor and cognitive function. We report a 14-year-old girl who developed epilepsia partialis continua involving the left hand, mild hemiparesis, and secondarily generalized seizures. RS was confirmed by brain biopsy. The patient has been treated with intravenous gamma globulin every 4 months for 46 months. The clinical course throughout this time has been distinctly atypical for RS, with no progression in motor or cognitive deficits and rare secondarily generalized seizures. Although the mechanism for action for gamma globulin in RS is not known, an immunomodulatory role has been postulated. Evidence of an immunologically mediated process in RS and clinical experience with a growing number of patients who benefit from immunomodulatory therapy suggest that a systematic study of the efficacy of gamma globulin in comparison with other forms of medical therapy is warranted.

The recurrent distal 22q11.2 microdeletions are often de novo and do not represent a single clinical entity: a proposed categorization system.

Purpose:The five segmental duplications (LCR22-D to -H) at the distal region of chromosome 22 band q11.2 in the region immediately distal to the DiGeorge/velocardiofacial syndrome deleted region have been implicated in the recurrent distal 22q11.2 microdeletions. To date, the distal 22q11.2 microdeletions have been grouped together as a single clinical entity despite the fact that these deletions are variable in size and position depending on the mediating LCR22s.Methods:Here, we report 13 new unrelated patients with variable size deletions in the distal 22q11.2 region as shown by cytogenomic array analyses. We compare our patients’ clinical features with those of previously reported cases to better dissect the phenotypic correlations based on the deletion size and position.Results:Six patients had the 1.1-Mb deletion flanked by LCR22-D and -E, and presented clinically with a phenotype consistent with previously reported cases with distal 22q11.2 microdeletions. Three patients had the 1.8-Mb deletion flanked by LCR22-D and -F, and presented with a similar phenotype. Four patients had the 700-kb deletion flanked by LCR22-E and -F, and presented with a milder phenotype that lacked growth restriction and cardiovascular defects.Conclusion:We suggest that the recurrent distal 22q11.2 microdeletions do not represent a single clinical entity, and propose categorizing these deletions into three types according to their genomic position. All three deletion types are thought to be pathogenic and are most often de novo. They all share some presenting features but also have their unique features and risks.Genet Med 16 1, 92–100.

Brain Tumors Presenting as a Seizure Disorder in Infants

Seizures occur in 25% to 40% of children with supratentorial tumors and are the presenting complaint in 10% to 15%. However, when divided by age, only 2% of children with seizures as the presenting complaint of brain tumors were less than 1 year of age. Three children, ranging in age from 20 days to 7 months and seen within the past 2 years, form the basis of this report. The presenting complaint in all children was seizures. Computed tomographic (CT) scan was indicated in all children because of intractability to anticonvulsant drug therapy (one patient) and focal electroencephalographic (EEG) abnormality with clinical evidence of complex partial seizure activity (two patients). CT scan showed a contrast-enhancing mass in the medial temporal lobe in all patients. At surgery, a temporal lobe tumor was found and resected in all children. Histopathologic examination revealed a ganglioglioma, a fibrillary astrocytoma, and an anaplastic astrocytoma. All children did well postoperatively and are seizure free to date. Our experience suggests that supratentorial tumors should be considered as a cause of intractable and/or focal seizures in children under 1 year of age, and that such tumors should be attacked aggressively neurosurgically. Our experience is also in agreement with that of Tadmor et al, who have suggested that with the advent of CT scanning supratentorial tumors in this age group have been found to be more common than previously realized. ( Child Neurol 1987;2:214-219)

Neurologic complications of immunizations

Although there does appear to be at least a temporal relationship between pertussis immunization and serious acute neurologic illness, data to suggest that children with stable preexisting neurologic disease or positive family history of neurologic disease are at increased risk for complications of pertussis immunizations are inconclusive. Furthermore, there are no firm statistical data concerning the incidence of pertussis vaccine-related encephalopathy. Rather, the literature on pertussis vaccine complications is replete with anecdotal reports and retrospective studies with a number of questionable conclusions drawn from this inadequate data base. Unfortunately, these conclusions have been sensationalized and exploited with litigious fervor to the point that the practice of pertussis immunization is being questioned in the United States. A number of points should be reiterated: pertussis is a dangerous and deadly disease, as seen in the epidemic in Great Britain; pertussis immunization is effective in protecting against the disease; and there is no conclusive proof that the incidence of complications from pertussis vaccination of children with seizure disorders or other preexisting stable neurologic abnormalities is higher, because appropriate studies have not been done to define such a risk. We would do well to keep these facts in mind in order to avoid a disaster similar to the pertussis epidemic in Great Britain. Pertussis vaccination should be given to all children except those with allergic hypersensitivity, a progressive neurologic disorder, or an adverse reaction to a previous pertussis dose.

Disruptive SCYL1 Mutations Underlie a Syndrome Characterized by Recurrent Episodes of Liver Failure, Peripheral Neuropathy, Cerebellar Atrophy, and Ataxia.

Hereditary ataxias comprise a group of genetically heterogeneous disorders characterized by clinically variable cerebellar dysfunction and accompanied by involvement of other organ systems. The molecular underpinnings for many of these diseases are widely unknown. Previously, we discovered the disruption of Scyl1 as the molecular basis of the mouse mutant mdf, which is affected by neurogenic muscular atrophy, progressive gait ataxia with tremor, cerebellar vermis atrophy, and optic-nerve thinning. Here, we report on three human individuals, from two unrelated families, who presented with recurrent episodes of acute liver failure in early infancy and are affected by cerebellar vermis atrophy, ataxia, and peripheral neuropathy. By whole-exome sequencing, compound-heterozygous mutations within SCYL1 were identified in all affected individuals. We further show that in SCYL1-deficient human fibroblasts, the Golgi apparatus is massively enlarged, which is in line with the concept that SCYL1 regulates Golgi integrity. Thus, our findings define SCYL1 mutations as the genetic cause of a human hepatocerebellar neuropathy syndrome.

ALG1-CDG: Clinical and Molecular Characterization of 39 Unreported Patients.

Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over 100 genes leading to impaired protein or lipid glycosylation. ALG1 encodes a β1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol‐lipid linked oligosaccharide intermediate required for proper N‐linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1‐CDG. To date 13 mutations in 18 patients from 14 families have been described with varying degrees of clinical severity. We identified and characterized 39 previously unreported cases of ALG1‐CDG from 32 families and add 26 new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1‐deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein‐linked xeno‐tetrasaccharide biomarker, NeuAc‐Gal‐GlcNAc2, was seen in all 27 patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.