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Pathogenic variants in the PCDH19 gene are associated with epilepsy, intellectual disability (ID) and behavioural disturbances. Only heterozygous females and mosaic males are affected, likely due to a disease mechanism named cellular interference. Until now, only four affected mosaic male patients have been described in literature. Here, we report five additional male patients, of which four are older than the oldest patient reported so far. All reported patients were selected for genetic testing because of developmental delay and/or epilepsy. Custom-targeted next generation sequencing gene panels for epilepsy genes were used. Clinical data were collected from medical records. All patients were mosaic in blood for likely pathogenic variants in the PCDH19 gene. In most, clinical features were very similar to the female phenotype, with normal development before seizure onset, which occurred between 5 and 10 months of age, clustering of seizures and sensitivity to fever. Four out of five patients had mild to severe ID and behavioural problems. We reaffirm the similarity between male and female PCDH19-related phenotypes, now also in a later phase of the disorder (ages 10-14 years).

Epilepsy and mental retardation limited to females (EFMR), caused by PCDH19 mutations, has a variable clinical expression that needs further exploration. Onset of epilepsy may be provoked by fever and can resemble Dravet syndrome. Furthermore, transmitting males have no seizures, but are reported to have rigid personalities suggesting possible autism spectrum disorders (ASD). Therefore, this study aimed to determine the phenotypic spectrum associated with PCDH19 mutations in Dravet-like and EFMR female patients and in males with ASD. We screened 120 females suffering from Dravet-like epilepsy, 136 females with EFMR features and 20 males with ASD. Phenotypes and genotypes of the PCDH19 mutation carriers were compared with those of 125 females with EFMR reported in the literature. We report 15 additional patients with a PCDH19 mutation. Review of clinical data of all reported patients showed that the clinical picture of EFMR is heterogeneous, but epilepsy onset in infancy, fever sensitivity and occurrence of seizures in clusters are key features. Seizures remit in the majority of patients during teenage years. Intellectual disability and behavioural disturbances are common. Fifty percent of all mutations are missense mutations, located in the extracellular domains only. Truncating mutations have been identified in all protein domains. One ASD proband carried one missense mutation predicted to have a deleterious effect, suggesting that ASD in males can be associated with PCDH19 mutations.

Recent array-based studies have detected a wealth of copy number variations (CNVs) in patients with autism spectrum disorders (ASD). Since CNVs also occur in healthy individuals, their contributions to the patient's phenotype remain largely unclear. In a cohort of children with symptoms of ASD, diagnosis of the index patient using ADOS-G and ADI-R was performed, and the Social Responsiveness Scale (SRS) was administered to the index patients, both parents, and all available siblings. CNVs were identified using SNP arrays and confirmed by FISH or array CGH. To evaluate the clinical significance of CNVs, we analyzed three families with multiple affected children (multiplex) and six families with a single affected child (simplex) in which at least one child carried a CNV with a brain-transcribed gene. CNVs containing genes that participate in pathways previously implicated in ASD, such as the phosphoinositol signaling pathway (PIK3CA, GIRDIN), contactin-based networks of cell communication (CNTN6), and microcephalin (MCPH1) were found not to co-segregate with ASD phenotypes. In one family, a loss of CNTN5 co-segregated with disease. This indicates that most CNVs may by themselves not be sufficient to cause ASD, but still may contribute to the phenotype by additive or epistatic interactions with inherited (transmitted) mutations or non-genetic factors. Our study extends the scope of genome-wide CNV profiling beyond de novo CNVs in sporadic patients and may aid in uncovering missing heritability in genome-wide screening studies of complex psychiatric disorders.

We describe the clinical presentation, radiological and clinical results in six consecutive patients with a giant vertebrobasilar aneurysm treated by bilateral vertebral artery balloon occlusion. Five patients presented with headache and signs of brain-stem compression and one with subarachnoid haemorrhage. In all patients vertebral artery balloon occlusion was performed. In four, this followed successful test occlusion. In one patient, who did not tolerate the test occlusion, a bypass from the external carotid to the posterior cerebral artery preceded definitive vertebral artery occlusion. One patient underwent bypass surgery prior to test occlusion. At 6-22 months follow-up three patients had a good functional outcome and showed unchanged size or shrinkage of the aneurysm on MRI. Three other patients died; one from recurrent haemorrhage, and two probably from delayed brain-stem ischaemia. The presence of two large posterior communicating arteries predicted good functional outcome, which was also related to the clinical condition at presentation, and the degree of brain-stem compression and oedema on MRI. Bilateral vertebral artery balloon occlusion can be considered in patients with otherwise untreatable giant vertebrobasilar aneurysms. If test occlusion is not tolerated, a surgical bypass to the posterior circulation can be considered.