Neonatal mitochondrial hepatoencephalopathy caused by novel GFM1 mutations

Disorders caused by defects in the mitochondrial translation system are clinically and genetically heterogeneous. The elongation phase of mitochondrial protein synthesis requires, among many other components, three nuclear-encoded elongation factors: EFTu (TUFM; 602389), EFTs (TSFM; 604723), and EFG1 (GFM1; 606639). Mutations have been identified in the genes encoding all three elongation factors, and they result in combined respiratory chain deficiencies and severe phenotypes with an early fatal outcome. So far, only eleven patients have been reported with mutations in GFM1. Here we describe an additional three patients with novel GFM1 mutations. Our results confirm the tissue-specific effect of GFM1 mutations, since we found only slightly decreased respiratory chain enzyme activities in muscle and fibroblasts, but a severe deficiency in the liver. Hence, a thorough biochemical evaluation is important to guide genetic investigation in patients suspected for a mitochondrial disorder

Two new cases with microdeletion of 17q23.2 suggest presence of a candidate gene for sensorineural hearing loss within this region

Microdeletion of the 17q23.2 region has very recently been suggested as a new emerging syndrome based on the finding of 8 cases with common phenotypes including mild-to-moderate developmental delay, heart defects, microcephaly, postnatal growth retardation, and hand, foot, and limb abnormalities. In this report, we describe two new 17q23.2 deletion patients with mild intellectual disability and sensorineural hearing loss. They both had submicroscopic deletions smaller than the common deleted region for the 8 previously described 17q23.2 microdeletion cases. TBX4 was previously suggested as the responsible gene for the heart or limb defects observed in 17q23.2 deletion patients, but the present cases do not have these features despite deletion of this gene. The finding of sensorineural hearing loss in 5 of the 10 cases, including the present cases, with a microdeletion at17q23.2, strongly suggests the presence of a candidate gene for hearing loss within this region. We screened 41 patients with profound sensorineural hearing loss for mutations of TBX2 and detected no mutations

Clinician's guide to genes associated with Rett-like phenotypes - Investigation of a Danish cohort and review of the literature

The differential diagnostics in Rett syndrome has evolved with the development of next generation sequencing-based techniques and many patients have been diagnosed with other syndromes or variants in newly described genes where the associated phenotype(s) is yet to be fully explored. The term Rett-like refers to phenotypes with distinct overlapping features of Rett syndrome where the clinical criteria are not completely fulfilled. In this study we have combined a review of Rett-like disorders with data from a Danish cohort of 35 patients with Rett-like phenotypes emphasizing the diagnostic overlap with Pitt-Hopkins syndrome, Cornelia de Lange syndrome with SMC1A variants, and epileptic encephalopathies, for example, due to STXBP1 variants. We also found a patient with a pathogenic variant in KCNB1, which has not been previously linked to a Rett-like phenotype. This study underlines the clinical and genetic heterogeneity of a Rett syndrome spectrum, and provides an overview of the Rett syndrome-related genes described to date, and hence serves as a guide for diagnosing patients with Rett-like phenotypes

Mutational analysis of TSC1 and TSC2 in Danish patients with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by hamartomas in the skin and other organs, including brain, heart, lung, kidney and bones. TSC is caused by mutations in TSC1 and TSC2. Here, we present the TSC1 and TSC2 variants identified in 168 Danish individuals out of a cohort of 327 individu

The <i>MECP2</i> variant c.925C&gt;T (p.Arg309Trp) causes intellectual disability in both males and females without classic features of Rett syndrome

Item does not contain fulltextMissense MECP2 variants can have various phenotypic effects ranging from a normal phenotype to typical Rett syndrome (RTT). In females, the phenotype can also be influenced by the X-inactivation pattern. In this study, we present detailed clinical descriptions of six patients with a rare base-pair substitution affecting Arg309 at the C-terminal end of the transcriptional repression domain (TRD). All patients have intellectual disability and present with some RTT features, but they do not fulfill the clinical criteria for typical or atypical RTT. Most of the patients also have mild facial dysmorphism. Intriguingly, the mother of an affected male patient is an asymptomatic carrier of this variant. It is therefore likely that the p.(Arg309Trp) variation does not necessarily lead to male lethality, and it results in a wide range of clinical features in females, probably influenced by different X-inactivation patterns in target tissues