OCLN gene variants identified in three patients with severe neurodevelopmental disorder associated with epilepsy, intellectual disability and malformation of cortical development.

Homozygous OCLN variants have been reported in patients with band-like calcification with simplified gyration and polymicrogyria (BLC-PMG) which is characterized by microcephaly, intracranial calcification and severe developmental delay. The OCLN gene encodes the integral membrane protein, occludin. Herein, we report three additional cases with homozygous OCLN variants that were identified via Trio-WES in two consanguineous unrelated families. We detected a previously reported frameshift variant in two cases in Family 1 and a novel missense variant in a case in Family 2. The potential pathogenicity of both variants in the index cases was investigated using in silico tools, and both variants were determined to be rare and predicted to be pathogenic. All of the presented cases exhibited clinical features in common with earlier reported patients, such as severe intellectual disability, microcephaly, polymicrogyria, epilepsy, hypotonia and severe developmental delay. On the other hand, in addition to the common phenotypic features, our two cases in Family 1 showed features similar to those previously reported in cases from two Turkish families carrying the same frameshift variant, such as renal failure. We herein expand the spectrum of OCLN gene variants with a description of an additional novel homozygous missense variant. The frameshift variant in Turkish cases may thus be a phenotype associated with renal failure in addition to the core phenotype associated with other OCLN gene variants, and such variants could be important for rapid molecular diagnosis and treatment. The frameshift variant in Turkish cases might also be investigated for both a potential founder effect and mutational hot spot.

A Rare Cause of Globus Pallidus and Dentate Nucleus Hyperintensity in Childhood: MBOAT Mutation.

Mutations in mammalian membrane-bound O-acyltransferase domain-containing (MBOAT) 7 gene are a rare cause for intellectual disability, developmental delay, autistic findings, epilepsy, truncal hypotonia with appendicular hypertonia, and below-average head sizes. Pathogenic variants in MBOAT7 gene show these nonspecific clinical features that are seen in many other neurometabolic diseases. Therefore, specific neuroimaging findings can be valuable key factors for differential diagnosis. Magnetic resonance imaging (MRI) findings of T2 hyperintensity in bilateral globus pallidi and dentate nuclei are seen in a few neurometabolic diseases with similar clinical features of developmental delay and hypotonia, as in our cases. While evaluating the patients with similar phenotypes and specific MRI findings, MBOAT7 deficiency should be kept in mind. Here, we identified two brothers who had a novel homozygous variant in MBOAT7 gene and aimed to raise awareness about this newly described disease.