Rett syndrome (RTT) is a severe neurological disorder usually caused by mutations in the MECP2 gene. Since the MECP2 gene is located on the X chromosome, X chromosome inactivation (XCI) could play a role in the wide range of phenotypic variation of RTT patients; however, classical methylation-based protocols to evaluate XCI could not determine whether the preferentially inactivated X chromosome carried the mutant or the wild-type allele. Therefore, we developed an allele-specific methylation-based assay to evaluate methylation at the loci of several recurrent MECP2 mutations. We analyzed the XCI patterns in the blood of 174 RTT patients, but we did not find a clear correlation between XCI and the clinical presentation. We also compared XCI in blood and brain cortex samples of two patients and found differences between XCI patterns in these tissues. However, RTT mainly being a neurological disease complicates the establishment of a correlation between the XCI in blood and the clinical presentation of the patients. Furthermore, we analyzed MECP2 transcript levels and found differences from the expected levels according to XCI. Many factors other than XCI could affect the RTT phenotype, which in combination could influence the clinical presentation of RTT patients to a greater extent than slight variations in the XCI pattern.

We describe a 4-year-old male child born to non-consanguineous Spanish parents with progressive encephalopathy (PE), microcephaly, and hypertonia. Whole exome sequencing revealed compound heterozygous BRAT1 mutations [c.1564G > A (p.Glu522Lys) and c.638dup (p.Val214Glyfs*189)]. Homozygous and compound heterozygous BRAT1 mutations have been described in patients with lethal neonatal rigidity and multifocal seizure syndrome (MIM# 614498). The seven previously described patients suffered from uncontrolled seizures, and all of those patients died in their first months of life. BRAT1 acts as a regulator of cellular proliferation and migration and is required for mitochondrial function. The loss of these functions may explain the cerebral atrophy observed in this case of PE. This case highlights the extraordinary potential of next generation technologies for the diagnosis of rare genetic diseases, including PE. Making a prompt diagnosis of PE is important for genetic counseling and disease management.

Nevus anemicus (NA) is a cutaneous anomaly characterized by pale, well-defined patches with limited vascularization after rubbing. They are largely known to be associated with neurofibromatosis 1 (NF1) and have received little attention in the literature until recently. We sought to characterize the prevalence and clinical features of patients with NA and NF1. We conducted an observational prospective study of 99 children with NF1 at the Hospital Niño Jesús, Madrid, Spain, from January 1, 2012, through July 31, 2013, and reviewed three other series of patients with NF1 and NA recently reported. The prevalence of NA in children with NF1 ranged from 8.8% to 51%, being much more prevalent at younger ages. Prospective studies yielded a higher prevalence than retrospective studies. NA was located most commonly on the trunk, particularly on the anterior chest wall, and was often multiple. Patients with segmental NF1 or isolated café au lait spots rarely had NA, and NA was absent in other genodermatoses. The collection of data was not homogeneous in all studies. NA has a high prevalence in individuals with NF1 patients but seems to be absent in connection with other genodermatoses, therefore its presence can assist in the diagnosis of suspected cases of NF1. The subtle clinical appearance of NA makes its detection difficult, and physicians involved in the care of children with NF1 must be aware of its possible presence and significance.

No abstract