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.

A novel RAD21 variant associated with intrafamilial phenotypic variation in Cornelia de Lange syndrome - review of the literature.

In a patient with CdLS (IV.16) we identifed a novel single basepair deletion (c.704delG) in RAD21, which encodes a cohesin pathway protein. The variant is predicted to result in a premature stop codon [p.(Ser235Ilefs*19)] and hereby would have a deleterious effect. RAD21 variants have previously been described only in five cases with cohesinopathies (b). Notably, the deletion was found in the mother and the two aunts of the index patient, and none of them had been suspected of having CdLS or a cohesinopathy prior to this study (a). The index patient can be classified as mild CdLS, but the other family members do not fulfill the diagnostic criteria of CdLS. This study together with previous reports suggests incomplete penetrance associated with RAD21 variants and these individuals may therefore be underdiagnosed.

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

Missense 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.

Cornelia de Lange syndrome.

Cornelia de Lange syndrome (CdLS; MIM #122470, 300590, 610759, 614701, 300882) is a rare and clinically variable disorder that affects multiple organs. It is characterized by intellectual disability (mild to severe), distinctive facial features, prenatal and postnatal growth retardation, and hirsutism. Congenital anomalies include malformations of the upper limbs, gastrointestinal malformation/rotation, pyloric stenosis, diaphragmatic hernia, heart defects and genitourinary malformations. Gastroesophageal reflux disease is present in almost all patients. In addition to classic forms, milder phenotypes have been reported. To date five genes [NIPBL (Nipped-B-like protein), SMC1A (structural maintenance of chromosomes 1A), SMC3 (structural maintenance of chromosomes 3), RAD21 (human homolog of Schizosaccharomyces pombe radiation sensitive mutant 21) and HDAC8 (histone deacetylase 8)] have been associated with CdLS and mutations of these genes comprise the underlying defect in 70% of the patients. Here, we will provide a brief review of the clinical features of CdLS, summarize the known underlying genetic defects, prenatal and postnatal diagnosis possibilities, and genetic counseling.

Chromosomal deletion unmasking a recessive disease: 22q13 deletion syndrome and metachromatic leukodystrophy.

A deletion on one chromosome and a mutant allele on the other may cause an autosomal recessive disease. We report on two patients with mental retardation, dysmorphic features and low catalytic activity of arylsulfatase A. One patient had a pathogenic mutation in the arylsulfatase A gene (ARSA) and succumbed to metachromatic leukodystrophy (MLD). The other patient had a pseudoallele, which does not lead to MLD. The presenting clinical features and low arylsulfatase A activity were explained, in each patients, by a deletion of 22q13 and, thereby, of one allele of ARSA.

4q35 deletion and 10p15 duplication associated with immunodeficiency.

We report a familial cryptic reciprocal translocation between 4q35 and 10p15 leading to deletion of the terminal long arm of chromosome 4 and duplication of the terminal short arm of chromosome 10 in two family members who both have immunological disturbances and a similar facial appearance. The precise location and extent of the deletion and duplication was determined by fluorescence in situ hybridization (FISH). Furthermore, we investigated the deletion breakpoint of a previously reported patient with 4q34.3-qter deletion [Van Buggenhout et al. (2004); Am J Med Genet Part A 131A:186-189].

Changes in body water distribution during treatment with inhaled steroid in pre-school children.

PRIMARY OBJECTIVE: The study aimed to examine the changes in water distribution in the soft tissue during systemic steroid activity. RESEARCH DESIGN: A three-way cross-over, randomized, placebo-controlled, double-blind trial was used, including 4 weeks of fluticasone propionate pMDI 200 microg b.i.d. delivered via Babyhaler, budesonide pressurized metered dose inhaler (pMDI) 200 microg b.i.d. delivered via Nebuchamber and placebo. Spacers were primed before use. In total, 40 children aged 1-3 years, with mild intermittent asthma were included. Twenty-five of the children completed all three treatments. At the end of each treatment period body impedance and skin ultrasonography were measured. METHODS AND PROCEDURES: We measured changes in water content of the soft tissues by two methods. Skin ultrasonography was used to detect small changes in dermal water content, and bioelectrical impedance was used to assess body water content and distribution. MAIN OUTCOMES AND RESULTS: We found an increase in skin density of the shin from fluticasone as measured by ultrasonography (p = 0.01). There was a tendency for a consistent elevation of impedance parameters from active treatments compared to placebo although overall this effect was not statistically significant (0.1 < p < 0.2). However, sub-analyses indicated a significant effect on whole-body and leg impedance from budesonide treatment (p < 0.05). CONCLUSION: Decreased growth during inhaled steroid treatment seems to partly reflect generalized changes in body water.