Helene Verhelst

Extending the phenotype of recurrent rearrangements of 16p11.2: deletions in mentally retarded patients without autism and in normal individuals.

Array CGH (comparative genomic hybridization) screening of large patient cohorts with mental retardation and/or multiple congenital anomalies (MR/MCA) has led to the identification of a number of new microdeletion and microduplication syndromes. Recently, a recurrent copy number variant (CNV) at chromosome 16p11.2 was reported to occur in up to 1% of autistic patients in three large autism studies. In the screening of 4284 patients with MR/MCA with various array platforms, we detected 22 individuals (14 index patients and 8 family members) with deletions in 16p11.2, which are genomically identical to those identified in the autism studies. Though some patients shared a facial resemblance and a tendency to overweight, there was no evidence for a recognizable phenotype. Autism was not the presenting feature in our series. The assembled evidence indicates that recurrent 16p11.2 deletions are associated with variable clinical outcome, most likely arising from haploinsufficiency of one or more genes. The phenotypical spectrum ranges from MR and/or MCA, autism, learning and speech problems, to a normal phenotype.

Blue native polyacrylamide gel electrophoresis: A powerful tool in diagnosis of oxidative phosphorylation defects

Catalytic activity of oxidative phosphorylation complexes is maintained following separation by Blue Native polyacrylamide gel electrophoresis (BN-PAGE). In BN-PAGE gels, using histochemical staining methods, we have demonstrated enzymatic activity of the complexes I, II, IV, and V in heart and skeletal muscle, liver, and cultured skin fibroblasts. The combination of BN-PAGE and catalytic staining can be successfully applied for detection of complex deficiencies. Tissues from 18 patients with deficiency in the oxidative phosphorylation as detected by spectrophotometric assay were used (10 patients complex IV, three patients complex I, one patient complex II, one patient complex I+III, three patients complex I+IV). The gene defect was located in nuclear DNA in five patients and mitochondrial DNA in one patient. In samples from patients with a severe deficiency, almost complete absence of the corresponding enzyme band is observed after catalytic staining in the gel. In patients with known partial deficiency, a milder decrease of the corresponding enzyme band is demonstrated. The amount of protein in complexes I, V, and III can easily be evaluated in samples from heart and skeletal muscle after separation by BN-PAGE using silver or Coomassie staining. The protein amount in complex IV is difficult to visualize by silver staining but easier by the Coomassie technique. In samples from liver and cultured skin fibroblasts, evaluation of protein amount is more difficult due to high background staining. In these tissues, immunoblotting can be done after BN-PAGE and subsequent transfer to a nitrocellulose membrane.

TUBA1A mutations From isolated lissencephaly to familial polymicrogyria

Background: Mutations in the TUBA1A gene have been reported in patients with lissencephaly and perisylvian pachygyria. Methods: Twenty-five patients with malformations of cortical development ranging from lissencephaly to polymicrogyria were screened for mutations in TUBA1A. Results: Two novel heterozygous missense mutations in TUBA1A were identified: c.629A>G (p.Tyr210Cys) occurring de novo in a boy with lissencephaly, and c.13A>C (p.Ile5Leu) affecting 2 sisters with polymicrogyria whose mother presented somatic mosaicism for the mutation. Conclusions: Mutations in TUBA1A have been described in patients with lissencephaly and pachygyria. We report a mutation in TUBA1A as a cause of polymicrogyria. So far, all mutations in TUBA1A have occurred de novo, resulting in isolated cases. This article describes familial recurrence of TUBA1A mutations due to somatic mosaicism in a parent. These findings broaden the phenotypic spectrum associated with TUBA1A mutations and have implications for genetic counseling.

Vagus nerve stimulation for refractory status epilepticus.

We report on the long-term follow-up of a patient with refractory non-convulsive SE who was successfully treated with VNS. A 7-year old girl with a medical history of thrombosis in the right internal cerebral vein and right thalamic bleeding 8 days after birth, developed epilepsy at the age of 13 months. At the age of 6 she presented with a refractory non-convulsive SE. A vagus nerve stimulator was placed after 11 days of thiopental-induced coma. Three days after VNS implantation, the thiopental-induced coma was successfully withdrawn and electroencephalography showed normalization one week after start of VNS. After a follow-up of 13 months she remains seizure-free and AEDs have been partially tapered. This case illustrates a potential acute abortive effect with sustained long-term seizure reduction of VNS in a 7-year old girl who presented with refractory non-convulsive SE.

Anti-NMDA-receptor encephalitis in a 3 year old patient with chromosome 6p21.32 microdeletion including the HLA cluster

Anti-NMDA-receptor encephalitis was initially described as a paraneoplastic disorder in young women with ovarian teratoma. We report on a 3-year-old boy who developed anti-NMDA-receptor encephalitis one month after a respiratory infection. Moreover, array-comparative genomic hybridization in this patient revealed an inherited microdeletion in chromosomeband 6p21.32, including the HLA-DPB1 and HLA-DPB2 genes. The clinical relevance of this microdeletion is discussed.

Subcomplexes of mitochondrial complex V reveal mutations in mitochondrial DNA

Complex V, site of the final step in oxidative phosphorylation, uses the proton gradient across the inner mitochondrial membrane for the production of ATP. It is a multi‐subunit complex composed of a catalytic domain (F1) and a membrane domain (F0) linked by two stalks. Subcomplexes of complex V containing the F1 domain have previously been reported in small series of patients. We report the results in tissue samples and/or cultured skin fibroblasts studied by blue native PAGE followed by activity staining in the gel. Catalytically active subcomplexes of complex V were detected in 66 tissues originating from 53 patients. In 29 of the latter (55%), a mitochondrial DNA (mtDNA) defect was identified. Twelve patients had a pathogenic point mutation in a mitochondrial tRNA, one a large mtDNA deletion, 12 showed mtDNA depletion and four had a mutation in the MT‐ATP6 gene. We conclude that the presence of subcomplexes of complex V is a valuable indicator in the detection of mtDNA defects.

Expanding the spectrum of MERS type 2 lesions, a particular form of encephalitis.

We report on a 13-year-old boy who presented with signs suggestive of encephalitis and in whom magnetic resonance imaging revealed lesions in the genu and splenium of the corpus callosum and symmetrical lesions bilaterally in the center semiovale. This clinical-radiologic entity was previously reported in the literature and was given the acronym MERS type 2 (mild encephalitis with reversible splenial) lesion. The clinical, radiologic, and biochemical characteristics of the patient with MERS type 2 lesions presented in this article show some differences with those in previously reported patients. His clinical recovery was particularly slow, cerebrospinal fluid was abnormal, and on magnetic resonance imaging the typical time course of MERS type 2 lesions resolving through a phase of solitary lesions in the splenium of the corpus callosum, the so-called type 1 lesions, was not seen. He is also the first patient in whom mycoplasma pneumoniae was found to be associated with MERS type 2 lesions. These findings further expand the spectrum of MERS type 2 lesions. The question raises whether the MERS type 2 lesion represents a new type of encephalitis or a particular radiologically recognizable subtype of postinfectious encephalitis. In the article, previously reported patients with MERS type 2 lesions are reviewed.

Hot-water epilepsy: a new Caucasian case

Hot-water epilepsy, a benign type of reflex epilepsy rarely seen in western countries, is described in a 10month-old Caucasian patient. A previously healthy 10-month-old Belgian boy presented with episodes of sudden activity arrest, glazedeyed staring, unresponsiveness, hypotonia and pallor followed by cyanosis, initiated 1 min after immersion in a warm (37 C) bath and lasting for about 1 min. Clonic movements were not seen. Post-ictal drowsiness was present. Bathing in lukewarm water (32 C) or showering did not prevent attacks. The family historywas negative for epilepsy and febrile seizures. Clinical examination, routine blood tests, X-ray film of the skull, cerebral CT scan, ophthalmological examination, inter-ictal standardEEG, 24 hEEG, cardial ultrasound and ECG were normal. An attempt was undertaken to provoke an attack by placing the patient in a hot bath (39.5 C)whilst EEG andECG registration and video monitoring were performed. Sixty seconds after immersion in the hot water, he became motionless, hypotonic, mildly cyanotic around the lips, unresponsive, and stared. The attack ended abruptly after 15 s. The EEG findings (Fig. 1) and clinical manifestations were synchronic. Ictal ECG, heart frequency, blood pressure and oxygen saturation revealed no abnormalities. Postictal drowsiness lasted for about 1 h. Seizures provoked by contact with hot water during bathing, known as hot-water epilepsy, water-immersion epilepsy or bathing epilepsy, is a benign type of reflex epilepsy rarely seen in western countries [3, 4,6], but more common in Turkey [1,2] and India [5]. Hot-water epilepsy is mostly seen in infants and children [1, 2, 3, 4,5] with a male:female ratio of 2–3:1 [1, 2, 3, 4,5]. Of the seizures, 67%–71% are of the complex partial type, with or without secondary generalisation [1, 3, 4,5]. About 33% are primarily generalised, usually tonicclonic [5]. Seizures may start with a sense of fear or wellbeing, vertigo, activity arrest, confused speech, visual and auditory hallucinations, or complex automatisms [1, 5,6]. Further symptoms include decrease or loss of consciousness, hypotonia or hypertonia, staring, rolling of the eyeballs, twitching facial muscles, focal convulsions, tonic-clonic convulsions and cyanosis [3, 4,6]. Seizures last from 30 s to 3 min and can manifest at any time during bathing [5,6]. There can be post-ictal headache or drowsiness [3,6]. Almost all cases of hot-water epilepsy are seen in otherwise healthy children [2, 3, 4,6] with normal neurological examination [1, 2, 3, 4, 5,6] and neuroimaging [1,5]. Interictal EEG is usually normal [4, 5,6], although diffuse aspecific changes can be seen in 15%–20% of cases [1, 4,5]. Ictal EEG shows focal, usually temporal, unilateral [3,6], rhythmic slow wave activity of high amplitude with secondary generalisation after a few seconds [3, 4,6], without spikes or spike waves [4]. As differential diagnosis, heat-induced vagal syncopes, febrile seizures, aquagenic urticaria and breathholding spells should be considered [3,4]. Diagnostic certainty can only be achieved by ictal video-EEG monitoring with simultaneous ECG recording [3]. Lowering water temperature [1, 2, 3, 4,5] or showering or sponging instead of bathing [3, 4,5] is usually sufficient to achieve seizure control. Anti-epileptic drugs, with usually good response [1, 3,5], are only indicated when these measures fail or when non-reflex epilepsy is associated [1, 3,4]. Since there is a tendency to spontaneous remission within a few months to years [1, 2, 4,5], withdrawal of medication should be undertaken after some time [4]. K. De Keyzer Department of Internal Medicine, Ghent University Hospital, Ghent, Belgium

Inborn errors in RNA polymerase III underlie severe varicella zoster virus infections

Varicella zoster virus (VZV) typically causes chickenpox upon primary infection. In rare cases, VZV can give rise to life-threatening disease in otherwise healthy people, but the immunological basis for this remains unexplained. We report 4 cases of acute severe VZV infection affecting the central nervous system or the lungs in unrelated, otherwise healthy children who are heterozygous for rare missense mutations in POLR3A (one patient), POLR3C (one patient), or both (two patients). POLR3A and POLR3C encode subunits of RNA polymerase III. Leukocytes from all 4 patients tested exhibited poor IFN induction in response to synthetic or VZV-derived DNA. Moreover, leukocytes from 3 of the patients displayed defective IFN production upon VZV infection and reduced control of VZV replication. These phenotypes were rescued by transduction with relevant WT alleles. This work demonstrates that monogenic or digenic POLR3A and POLR3C deficiencies confer increased susceptibility to severe VZV disease in otherwise healthy children, providing evidence for an essential role of a DNA sensor in human immunity.

LIMBIC ENCEPHALITIS AS PRESENTATION OF A SAP DEFICIENCY

X-linked lymphoproliferative disease (XLP) is a rare immune cell disorder caused by mutations in the Src homology 2 domain-containing gene 1A (SH2D1A). This gene, located on the X-chromosome, encodes a small cytoplasmic adaptor known as signaling lymphocytic activation molecule (SLAM) associated protein (SAP). SAP is expressed in natural killer cells (NK) and T-cells. It interacts with SLAM and plays a critical role in regulating signaling.1 Clinical manifestations of patients with XLP vary. Most patients die following exposure to Epstein Barr virus (EBV). Boys who survive an EBV infection may develop dysgammaglobulinemia, lymphoma (usually B-cell type), or, less frequently, aplastic anemia, lymphoid granulomatosis, or vasculitis.2–4 Survival into adulthood is rare, although patients treated successfully by bone marrow transplantation (BMT) are recorded.5 Limbic encephalitis is characterized by profound memory impairment, dementia, seizures, usually complex partial, and psychiatric disturbances. On MRI, signal changes are detected on the medial sides of the temporal lobes or in the hippocampi.6,7 We report a patient with limbic encephalitis caused by SAP deficiency. ### Case report. The medical history of the propositus was noteworthy. At age 9 he was …