Case Report: Precision genetic diagnosis in a case of Dyggve-Melchior-Clausen syndrome reveals paternal isodisomy and heterodisomy of chromosome 18 with imprinting clinical implications.

A twelve-year-old patient with a previous clinical diagnosis of spondylocostal skeletal dysplasia and moderate intellectual disability was genetically analyzed through next generation sequencing of a targeted gene panel of 179 genes associated to skeletal dysplasia and mucopolysaccharidosis in order to stablish a precision diagnosis. A homozygous nonsense [c.62C>G; p.(Ser21Ter)] mutation in DYM gene was identified in the patient. Null mutations in DYM have been associated to Dyggve-Melchior-Clausen syndrome, which is a rare autosomal-recessive disorder characterized by skeletal dysplasia and mental retardation, compatible with the patient´s phenotype. To confirm the pathogenicity of this mutation, a segregation analysis was carried out, revealing that the mutation p(Ser21Ter) was solely inherited from the father, who is a carrier of the mutation, while the mother does not carry the mutation. With the suspicion that a paternal disomy could be causing the disease, a series of microsatellite markers in chromosome 18, where the DYM gene is harbored, was analyzed in all the members of the family. Haplotype analysis provided strong evidence of paternal isodisomy and heterodisomy in that chromosome, confirming the pathological effect of this mutation. Furthermore, the patient may have a compromised expression of the ELOA3 gene due to modifications in the genomic imprinting that may potentially increase the risk of digestive cancer. All these results highlight the importance of obtaining a precision diagnosis in rare diseases.

Brief Report: Evidence of Autism Spectrum Disorder Caused by a Mutation in ATRX Gene: A Case Report.

ATRX mutations are commonly associated with alpha-thalassaemia mental retardation syndrome (ATR-X syndrome) with a notable variable expressivity. This X-linked disorder is characterized by intellectual disability (ID) in a higher or lesser degree, in which the alpha-thalassaemia feature is not always present. Other phenotypic manifestations like facial dimorphism, hypotonia, microcephaly, skeletal abnormalities or urogenital malformations have been frequently observed in ATR-X syndrome. Herein, we report a missense ATRX mutation (Thr1621Met) in a patient with an autism spectrum disorder (ASD) diagnosis. Except for ID, no typical signs of ATR-X syndrome were found in the patient. These results confirm the extensive phenotypic variability associated to ATRX mutations and show the involvement of this gene in the ASD.

Tonic Seizure Status Epilepticus Triggered by Valproate in a Child with Doose Syndrome.

Antiepileptic drugs may occasionally increase seizure frequency or eliciting de novo seizure occurrence; the underlying mechanism of these effects is not known. The potential adverse effects of valproic acid in myoclonic astatic epilepsy have been noted by experienced clinicians in various different regions of the world, but this important observation has not been sufficiently reported. We present the case of tonic status epilepticus in an 8-year-old boy with Doose syndrome related to valproic acid. Valproic acid, such as others antiepileptic drugs, is liable to produce paradoxical effects such as the atypical seizures we report. We emphasize the importance for the management of acute seizures in an intensive care unit setting and increase awareness of the acute toxic effects of antiepileptic drugs.

A 2.84 Mb deletion at 21q22.11 in a patient clinically diagnosed with Marden-Walker syndrome.

We present a girl with the characteristic clinical picture associated with Marden-Walker syndrome (MWS; OMIM 248700), including mask-like face with blepharophimosis, joint contractures, intellectual disability, a multicystic dysplastic kidney and cerebral dysgenesis. The long-term follow-up allowed us to monitor the evolution of the phenotype in this patient, and among the main findings we highlight the following: demyelination of the pyramidal tract demonstrated by transcranial magnetic stimulation and the involvement of the levator muscles of angle of mouth in fixed facial expression with relative integrity of the rest of the facial expression muscles. A 244 k array comparative genomic hybridization (aCGH) was carried out and showed a de novo interstitial deletion of approximately 2.84 Mb affecting only the cytoband 21q22.11 (genome coordinates chr21:31,874,016-34,711,763). We selected 10 of the most recent published cases with either total or partial deletions of cytoband 21q22.11 that provided good characterization of the genomic size or the genes in the deleted regions. We observed that in nine of the 10 cases the deleted regions included the RUNX1 gene in 21q22.12, which is not affected in the current patient's deletion or in that of Patient 3 from Roberson et al. [2011]. After a comparison of shared deleted genes between cases, and correlation of their potential phenotypes, we concluded that the pattern of defects considered for a diagnosis of MWS may represent part of the phenotypic expression of a partial or total deletion of 21q22.11.

Periodic Lateralized Epileptiform Discharges (PLEDs) and pneumococcal meningoencephalitis.

Pneumococcal meningoencephalitis (PME) is a life-threatening condition of the central nervous system (CNS), and is often the result of a complicated upper airway infection. Periodic Lateralized Epileptiform Discharges (PLEDs) are a typical electroencephalographic (EEG) pattern found in some acutely acquired brain insults. Within the pediatric population they are frequently seen in association with herpetic encephalitis, a CNS infection with a high morbidity and mortality rate. We report the case of a 3-year-old girl with a bilateral ear infection who developed convulsions and coma. She had early PLEDs lateralized to the right on the EEG and microbiological criteria for Streptococcus pneumoniae infection. Concomitant herpetic encephalitis was ruled out. Intensive antibiotic and antiepileptic treatment resulted in a remarkable improvement, with the patient being able to resume her normal activities within months. To our knowledge, the association of PME and PLEDs has not been previously described in children. On the other hand, EEG has scarcely been used in the management of acute CNS infections. Hence, non-herpetic CNS encephalitis with potentially more favorable outcomes ought to be considered in the differential diagnosis of PLEDs. Continuous EEG monitoring should be considered in children with CNS infections presenting with altered sensorium, independent of the presence of seizures.

Atypical glycine encephalopathy in an extremely low birth weight infant: description of a new mutation and clinical and electroencephalographic analysis.

We present the clinical course and EEG evolution of an extreme low birth weight preterm neonate with an uncommon type of glycine encephalopathy. The patient presented with myoclonic jerks, apnea and encephalopathy three months after birth without satisfactory therapeutic response. During the first days of clinical symptoms the patient presented a paroxystic burst-attenuation EEG pattern which progressively evolved into an established typical burst-suppression pattern within a few days. West syndrome occurred four weeks later and the patient died at seven months of extra-uterine life due to a serious respiratory infection with cardio-respiratory arrest. Genetic analysis showed a non-previously described mutation affecting a consensus splice site (IVS2-1G > C 3) in the AMT gene encoding the T protein of the glycine cleavage system.