Update on the ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome

Baraitser-Winter cerebrofrontofacial syndrome is caused by heterozygous missense mutations in one of the two ubiquitous cytoplasmic actin-encoding genes ACTB and ACTG1. Recently, we characterized the large cohort of 41 patients presenting with this condition. Our series contained 34 patients with mutations in ACTB and only nine with ACTG1 mutations. Here, we report on seven unrelated patients with six mutations in ACTG1-four novel and two previously reported. Only one of seven patients was clinically diagnosed with this disorder and underwent ACTB/ACTG1 targeted sequencing, four patients were screened as a part of the large lissencephaly cohort and two were tested with exome sequencing. Retrospectively, facial features were compatible with the diagnosis but significantly milder than previously reported in four patients, and non-specific in one. The pattern of malformations of cortical development was highly similar in four of six patients with available MRI images and encompassed frontal predominant pachygyria merging with the posterior predominant band heterotopia. Two remaining patients showed mild involvement consistent with bilaterally simplified gyration over the frontal lobes. Taken together, we expand the clinical spectrum of the ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome demonstrating the mild end of the facial and brain manifestations. © 2016 Wiley Periodicals, Inc.

Microdeletion of chromosome 15q26.1 in a child with intractable generalized epilepsy

Chromosomal abnormalities involving deletions and duplications are known to cause severe developmental disorders, including mental retardation, dysmorphism, and seizures, in children. As the technique of array-based comparative genomic hybridization is being applied more frequently in the diagnostic evaluation of children with developmental disorders, novel pathologic chromosomal abnormalities are being identified. We report the case of a 9-year-old girl with a history of pervasive developmental disorder, growth delay, mild dysmorphic features, and intractable primary generalized epilepsy with a de novo microdeletion of approximately 0.73-0.94 Mb within chromosome 15q26.1. A much larger (5 Mb) but overlapping microdeletion has been previously reported in a 30-month-old child with similar phenotype including intractable myoclonic epilepsy, growth delay, and dysmorphic features. This leads us to propose that a potential candidate gene or genes within the deleted region involved in the pathogenesis of some forms of generalized intractable epilepsy, previously considered to be idiopathic.

Comprehensive mutation analysis ofGLDC,AMT, andGCSHin nonketotic hyperglycinemia

Nonketotic hyperglycinemia (NKH) is an inborn error of metabolism characterized by accumulation of glycine in body fluids and various neurological symptoms. NKH is caused by deficiency of the glycine cleavage multi-enzyme system with three specific components encoded by GLDC, AMT, and GCSH. We undertook the first comprehensive screening for GLDC, AMT, and GCSH mutations in 69 families (56, six, and seven families with neonatal, infantile, and late-onset type NKH, respectively). GLDC or AMT mutations were identified in 75% of neonatal and 83% of infantile families, but not in late-onset type NKH. No GCSH mutation was identified in this study. GLDC mutations were identified in 36 families, and AMT mutations were detected in 11 families. In 16 of the 36 families with GLDC mutations, mutations were identified in only one allele despite sequencing of the entire coding regions. The GLDC gene consists of 25 exons. Seven of the 32 GLDC missense mutations were clustered in exon 19, which encodes the cofactor-binding site Lys754. A large deletion involving exon 1 of the GLDC gene was found in Caucasian, Oriental, and black families. Multiple origins of the exon 1 deletion were suggested by haplotype analysis with four GLDC polymorphisms. This study provides a comprehensive picture of the genetic background of NKH as it is known to date.

Anoxic-epileptic seizures: home video recordings of epileptic seizures induced by syncopes

Occasionally, but more often than has been reported, true epileptic seizures are triggered by non-epileptic syncopes. This combination of syncope and epileptic seizure has been called an anoxic-epileptic seizure. A few examples of such anoxic-epileptic seizures, including the induction of status epilepticus, have been reported in books and medical journals, but no video-recordings have been published. We show here home video recordings of the first three known examples of the transition from the triggering syncope and anoxic seizure, to the subsequent epileptic seizure. In the first two children, a neurally-mediated syncope, probably mediated by prolonged expiratory apnoea (so-called breath-holding spells), induces a long, clonic epileptic seizure with some features of myoclonic absence. In the third example, a compulsive Valsalva in an older autistic child provokes a vibratory tonic epileptic seizure. In addition, we show two further video clips of the most usual type of epileptic seizure induced by syncopes in very young children. In one, the video recording begins after the end of the triggering syncope and shows a rhythmic clonic seizure that includes repetitive vocalizations. The final recoding is of a spontaneous epileptic seizure with features of myoclonic absence: this child had both epilepsy and identical episodes induced by syncopes, that is, anoxic- epileptic seizures. Not only paediatricians and paediatric neurologists, but also adult neurologists and epileptologists in general, should be aware of the important clinical scenario of true epileptic seizures induced by syncopes. This phenomenon is not considered in any international classification. (Published with videosequences)

Enzymatic diagnostic test for Muscle-Eye-Brain type congenital muscular dystrophy using commercially available reagents

OBJECTIVES

Mutations disrupting the interaction of extra-cellular ligands and alpha-dystroglycan are responsible for an etiologically heterogeneous group of autosomal recessive congenital muscular dystrophies (CMD) that can have associated brain and eye abnormalities. The objective is to develop a diagnostic test for one of these CMDs, Muscle-Eye-Brain disease (MEB), due to mutations in the gene encoding Protein O-Mannosyl beta-1,2-N-acetylglucosaminyltransferase 1 (POMGnT1).

DESIGN AND METHODS

POMGnT1 enzyme activity was determined in extracts of muscle biopsies from four MEB patients and various controls using commercially available reagents.

RESULTS

All four MEB muscle samples showed a highly significant decrease in POMGnT1 activity relative to controls.

CONCLUSIONS

The assay of POMGnT1 activity in MEB muscle provides a rapid and relatively simple diagnostic test for this disease. CMDs associated with brain malformations such as MEB, WWS and FCMD are heterogenous in clinical presentation and on radiologic examination, suggesting that POMGnT1 assays of muscle biopsies should be used as a screening procedure for MEB in all CMD patients associated with brain malformations.

Childhood-onset ataxia: testing for large CAG-repeats in SCA2 and SCA7

Infantile- and juvenile-onset spinal cerebellar ataxia (SCA) is associated with expansion of 130 to more than 200 CAG-repeats in the SCA2 and SCA7 genes. Routine clinical assays for SCA2 and SCA7, which use polymerase chain reaction (PCR) and denaturing PAGE (polyacrylamide gel electrophoresis), will not reliably detect such large expansions. An assay based on separation of PCR products on an agarose gel, blotting, and hybridization with a (CAG)6 oligonucleotide probe was used to test DNA from individuals more than 10 years of age who had a possible diagnosis of SCA. Among 25 cases, the PCR-blot assay confirmed the presence of SCA2 expansions between 230 and 500 repeats in four unrelated individuals, but did not detect any cases of extreme expansion in the SCA7 gene. The PCR-blot assay provides reliable detection of extreme expansion mutations. Routine incorporation of this assay in clinical laboratories may reveal that infantile-juvenile forms of SCA2 and SCA7 are more prevalent than previously recognized.

Analysis of a very large trinucleotide repeat in a patient with juvenile Huntington's disease

A patient with juvenile Huntington's disease (HD) of probable maternal inheritance is reported. The expanded IT-15 allele was only detected with the use of modified PCR and Southern transfer techniques, which showed a CAG trinucleotide repeat expansion of approximately 250 repeats-the largest CAG expansion reported within the huntingtin gene. This case emphasizes the need for communication between the diagnostic laboratory and the clinician to define the molecular genetics of unusual cases.

Bilateral periventricular nodular heterotopia with mental retardation and syndactyly in boys: a new X-linked mental retardation syndrome

Bilateral periventricular nodular heterotopia (BPNH) is a recently recognized malformation of neuronal migration, and perhaps proliferation, in which nodular masses of gray matter line the walls of the lateral ventricles. Most affected individuals have epilepsy and normal intelligence with no other congenital anomalies. A striking skew of the sex ratio has been observed because 31 of 38 probands have been female, and one gene associated with BPNH was recently mapped to chromosome Xq28. We report three unrelated boys with a new multiple congenital anomaly-mental retardation syndrome that consists of BPNH, cerebellar hypoplasia, severe mental retardation, epilepsy, and syndactyly. Variable abnormalities included focal or regional cortical dysplasia, cataracts, and hypospadius. We hypothesize that this syndrome involves the same Xq28 locus as isolated BPNH, and we review the expanding number of syndromes associated with BPNH.

Congenital Pick cell encephalopathy: a distinct disorder characterized by diffuse formation of Pick cells in the cerebral cortex

Diffuse degeneration of the cerebral cortex and claustrum was found in the brain of a 7-week-old baby with profound psychomotor retardation, multiple ankyloses, seizures, and hypothalamic dysfunction. There was ubiquitous Pick cell formation and gliosis in the affected gray matter. The cortex was not atrophic; in fact, the brain was moderately enlarged. The clinical and pathological findings suggest that the disorder should be distinguished from Pick's disease, as well as from other congenital encephalopathies.

Cardiac and skeletal myopathy associated with cardiac dysrhythmias

Electrophysiologic studies, echocardiograms, cardiac catheterizations and histologic and biochemical analyses of skeletal muscle biopsies were performed in 10 patients (aged 10 to 37 years, mean 21) who had dysrhythmias as the initial manifestation of cardiomyopathy. Presenting symptoms and signs attributable to dysrhythmias included sudden cardiac arrest in 2 patients, syncope in 3, presyncope in 3 and palpitations in 2. There was no clinical evidence of skeletal muscle weakness in any patient. Multicatheter electrophysiologic evaluation established diagnoses of ventricular tachycardia in 6 patients, primary atrial tachycardia in 2 and third degree infra-Hisian heart block in 1 patient. One patient presenting with palpitations had no inducible arrhythmia or conduction disturbance. Echocardiographic, angiographic and hemodynamic studies demonstrated previously unsuspected dilated cardiomyopathy in 7 patients and restrictive cardiomyopathy in 3. Skeletal muscle histologic characteristics were abnormal in all 10 patients; increases in lipid droplets and endomysial fibrosis were the characteristic findings. Serum free carnitine and short- and long-chain acylcarnitine were normal in 9 patients. However, skeletal muscle long-chain acylcarnitine was reduced in 9 patients. These findings support the concept that in certain patients presenting with dysrhythmias, the dysrhythmia may be a manifestation of cardiac and skeletal (that is, generalized) myopathy.

Emerging characteristics of the acoustic reflex in infants

One hundred ninety-nine infants (birth to 15 weeks) were administered an impedance battery to describe emerging characteristics of the acoustic reflex in this age range. Tympanometry results suggest that the middle ear system changes from a highly flaccid state at birth to a relatively normal compliance by 15 weeks. Acoustic reflexes were observed infrequently in the newborn population and gradually increased as a function of age, but never exceeding 43% of the ears tested. A conservative approach regarding the relevance of the presence of the reflex in young children is warranted.