Severe Thoracic and Spinal Bone Abnormalities in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is an autosomal dominant, multi-system, neurocutaneous disorder that predisposes to the development of benign and malignant tumors. Classical skeletal abnormalities encompass sphenoid wing dysplasia, congenital bowing of the long bones and vertebral osteopathy associated with non-dystrophic or dystrophic scoliosis found in about 10% of NF1 patients. We report a 17-year-old boy affected by NF1 with extreme severe spinal and thoracic malformations affecting bone and lung tissues, including hypoplasia of the right lung, unilateral costal agenesis and severe dystrophic scoliosis characterized by association of hemivertebra, fusion of adjacent vertebral bodies and defective pedicles. At birth, he presented an acute respiratory distress requiring invasive ventilator support. The diagnosis of NF1 was confirmed at age 5 by the identification of a de novo heterozygous mutation c.4537C > T, p.Arg1513* in NF1. Trio-based Whole Exome Sequencing (WES) was performed to exclude coexistence of a second hit but no clearly other pathogenic variant has been identified. Until now, only one similar NF1 patient suffering from the same association of severe scoliosis and chest deformity leading to respiratory insufficiency was described. The severe prenatal NF1-related scoliosis could explain the lung abnormal development by absence of mechanical constraints. Severe Thoracic and Spinal Bone Abnormalities may be part of the NF1 bone phenotype and should be taken into account to allow adequate genetic counseling.

IL11RA-related Crouzon-like autosomal recessive craniosynostosis in 10 new patients: Resemblances and differences.

By describing 10 new patients recruited in centres for Human Genetics, we further delineate the clinical spectrum of a Crouzon-like craniosynostosis disorder, officially termed craniosynostosis and dental anomalies (MIM614188). Singularly, it is inherited according to an autosomal recessive mode of inheritance. We identified six missense mutations in IL11RA, a gene encoding the alpha subunit of interleukin 11 receptor, 4 of them being novel, including 2 in the Ig-like C2-type domain. A subset of patients had an associated connective tissue disorder with joint hypermobility and intervertebral discs fragility. A smaller number of teeth anomalies than that previously reported in the two large series of patients evaluated in dental institutes points toward an ascertainment bias.

Further delineation of the phenotype caused by biallelic variants in the WDR4 gene.

Microcephalic primordial dwarfisms are a group of rare Mendelian disorders characterized by severe growth retardation and microcephaly. The molecular basis is heterogeneous, with disease-causing genes implicated in different cellular functions. Recently, 2 patients were reported with the same homozygous variant in the WDR4 gene, coding for an enzyme responsible for the m7 G46 post transcriptional modification of tRNA. We report here 2 sisters harboring compound heterozygous variants of WDR4. Their phenotype differs from that of the first 2 described patients: they both have a severe microcephaly but only one of the 2 sisters had a head circumference at birth below -2 SD, their intellectual deficiency is less severe, and they have a growth hormone deficiency and a partial hypogonadotropic hypogonadotropism. One of the 2 variants is a frameshift mutation, and the other one is a missense occurring in the same nucleotide affected by the first reported pathogenic variant, which could therefore be a mutational hot spot. The description of these 2 sisters allow us to confirm that biallelic variants in the WDR4 gene can lead to a specific phenotype, characterized by severe growth retardation and microcephaly.