Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients

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IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients

Purpose

Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.

Methods

We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.

Results

IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.

Conclusion

This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.

The mitochondrial solute carrier SLC25A5 at Xq24 is a novel candidate gene for non-syndromic intellectual disability

Loss-of-function mutations in several different neuronal pathways have been related to intellectual disability (ID). Such mutations often are found on the X chromosome in males since they result in functional null alleles. So far, microdeletions at Xq24 reported in males always have been associated with a syndromic form of ID due to the loss of UBE2A. Here, we report on overlapping microdeletions at Xq24 that do not include UBE2A or affect its expression, in patients with non-syndromic ID plus some additional features from three unrelated families. The smallest region of overlap, confirmed by junction sequencing, harbors two members of the mitochondrial solute carrier family 25, SLC25A5 and SLC25A43. However, identification of an intragenic microdeletion including SLC25A43 but not SLC25A5 in a healthy boy excluded a role for SLC25A43 in cognition. Therefore, our findings point to SLC25A5 as a novel gene for non-syndromic ID. This highly conserved gene is expressed ubiquitously with high levels in cortex and hippocampus, and a presumed role in mitochondrial exchange of ADP/ATP. Our data indicate that SLC25A5 is involved in memory formation or establishment, which could add mitochondrial processes to the wide array of pathways that regulate normal cognitive functions.

Characterization by array-CGH of an interstitial de novo tandem 6p21.2p22.1 duplication in a boy with epilepsy and developmental delay

We report on a 6-years-old boy with psychomotor retardation, mild dysmorphic features and behavioral disturbances associated with epilepsy. Conventional cytogenetic analysis concluded to an interstitial de novo 6p21.2p22.3 duplication. Molecular cytogenetic analysis, including array-CGH technology, allows characterization of this 7.3Mb interstitial tandem duplication. The phenotype of this small 6p duplication reported to date is compared to other cases in the literature. Presence of epilepsy, although rare in patients with 6p duplication may be linked to genes involved in brain function and synaptic transmission in the 6p21.2p22.1 duplicated region (GABBR1, BRD2 and GRM4).

[Cerebral agyria-pachygyria in a child with Werdnig-Hoffmann disease]

Werdnig-Hoffmann disease refers to the severe infantile form of anterior horn cell degeneration. We report an association between Werdnig-Hoffmann disease and agyria-pachygyria. Examples of anterior horn cell disease with lesions in the central nervous system (notably thalamus and cerebellum) have been considered unusual "variants" of Werdnig-Hoffmann disease. This association between Werdnig-Hoffmann disease and agyria-pachygyria has, to our knowledge, never been described.

[Fetal cerebral ventriculomegaly. Etiology and outcome, report of 141 cases]

OBJECTIVE

To present the different etiologies of fetal cerebral ventriculomegaly (VA) and try to evaluate prognosis.

MATERIALS AND METHODS

A retrospective analysis was made in 141 cases of fetal cerebral ventriculomegaly diagnosed in our obstetrics department between January 1988 and December 1996.

RESULTS

Mean gestational age at diagnosis was 24.8 weeks. Myelomeningoceles were the most frequent etiology (50 cases, 36%), usually diagnosed late in pregnancy (25 weeks gestation). Termination of pregnancy was the most frequent outcome. Agenesis of the corpus callosum (ACC) was observed in 16 cases (11%), 8 of them being diagnosed before birth. This etiology has been an important diagnostic problem until recent years. The advent of improved imaging techniques has facilitated diagnostic procedures. Thus in 1996, the 4 ACC were all diagnosed by prenatal ultrasound. The 8 live infants presented developmental retardation. Termination of pregnancy has been performed more and more frequently in accordance with parent wishes. In 6 cases (4%), the etiology was congenital infection. When a chromosome anomaly was found (7%), ventriculomegaly was always associated with other ultrasonographic anomalies. Ventriculomegaly was associated with other malformations in 23% of the cases but only 17% were discovered prenatally; all the live infants but one had severe neurological impairment. Ventriculomegaly was considered to be the unique anomaly in 37% of the prenatal cases and was truly unique in 24%, an etiology being found in 6%. No explanation was found in 18%. The outcome of live infants is known in 139 cases (2 children lost to follow-up) after a 6 month to 6 year follow-up. Overall prognosis was severe as among the 42 infants (30%), 14 (10%) are well including 12 who had ventriculomegaly alone.

CONCLUSION

Prenatal diagnosis of ventriculomegaly implies a severe prognosis. Only children presenting limited ventriculomegaly alone have normal neurological development. In case of ventriculomegaly, clinicians must search carefully for other anomalies, always associated with poor prognosis.