Eight further individuals with intellectual disability and epilepsy carrying bi-allelic CNTNAP2 aberrations allow delineation of the mutational and phenotypic spectrum.

BACKGROUND: Heterozygous copy number variants (CNVs) or sequence variants in the contactin-associated protein 2 gene CNTNAP2 have been discussed as risk factors for a wide spectrum of neurodevelopmental and neuropsychiatric disorders. Bi-allelic aberrations in this gene are causative for an autosomal-recessive disorder with epilepsy, severe intellectual disability (ID) and cortical dysplasia (CDFES). As the number of reported individuals is still limited, we aimed at a further characterisation of the full mutational and clinical spectrum. METHODS: Targeted sequencing, chromosomal microarray analysis or multigene panel sequencing was performed in individuals with severe ID and epilepsy. RESULTS: We identified homozygous mutations, compound heterozygous CNVs or CNVs and mutations in CNTNAP2 in eight individuals from six unrelated families. All aberrations were inherited from healthy, heterozygous parents and are predicted to be deleterious for protein function. Epilepsy occurred in all affected individuals with onset in the first 3.5 years of life. Further common aspects were ID (severe in 6/8), regression of speech development (5/8) and behavioural anomalies (7/8). Interestingly, cognitive impairment in one of two affected brothers was, in comparison, relatively mild with good speech and simple writing abilities. Cortical dysplasia that was previously reported in CDFES was not present in MRIs of six individuals and only suspected in one. CONCLUSIONS: By identifying novel homozygous or compound heterozygous, deleterious CNVs and mutations in eight individuals from six unrelated families with moderate-to-severe ID, early onset epilepsy and behavioural anomalies, we considerably broaden the mutational and clinical spectrum associated with bi-allelic aberrations in CNTNAP2.

Multiple long bone cysts revealed by MRI in trichorhinophalangeal syndrome type II predisposing to pathological fractures.

Trichorhinophalangeal syndrome type II is a rare genetic disorder with the few published case reports mainly reporting the radiographic skeletal manifestations. There are no published imaging reports of long bone cysts involving multiple bones in this condition. We report a unique case of bone cysts involving multiple long bones detected with MRI in a patient with trichorhinophalangeal syndrome type II complicated by a subsequent pathological fracture. It is possible that the bone cysts are a previously undescribed feature of this syndrome; however, the evidence is insufficient to establish a definite association. Chromosomal abnormality identified in this patient is consistent with trichorhinophalangeal syndrome type II with no unusual features. Although the nature of these bone cysts is unclear, they are one of the causes of the known increased fracture risk observed in this syndrome.

Hypomorphic function and somatic reversion of DOCK8 cause combined immunodeficiency without hyper-IgE.

Loss-of-function mutations in DOCK8 are linked to hyper-IgE syndrome. Patients typically present with recurrent sinopulmonary infections, severe cutaneous viral infections, food allergies and elevated serum IgE. Although patients may present with a spectrum of disease-related symptoms, molecular mechanisms explaining phenotypic variability in patients are poorly defined. Here we characterized a novel compound heterozygous mutation in DOCK8 in a patient diagnosed with primary combined immunodeficiency which was not typical of classical DOCK8 deficiency. In contrast to previously identified mutations in DOCK8 which result in complete loss of function, the newly identified single nucleotide insertion results in expression of a truncated DOCK8 protein. Functional evaluation of the truncated DOCK8 protein revealed its hypomorphic function. In addition we found somatic reversion of DOCK8 predominantly in T cells. The combination of somatic reversion and hypomorphic DOCK8 function explains the milder and atypical phenotype of the patient and further broadens the spectrum of DOCK8-associated disease.

Pure de novo partial trisomy 6p in a girl with craniosynostosis.

Duplications of chromosome 6p are rarely reported. We present the case of a girl with a de novo trisomy 6p12.3-p21.1 who showed clinical features characteristic of this syndrome, notably facial anomalies, psychomotor delay, and recurrent respiratory tract infections. The most striking feature, however, was craniosynostosis, manifested by the premature fusion of the right coronal and sagittal sutures. A review of the literature revealed that the presence of abnormal fontanelles and sutures is relatively common among patients with proximal trisomy 6p. Exclusion of the most frequently occurring craniosynostosis mutations, as well as of further chromosomal anomalies in our case, suggest the presence of a gene regulating suture formation within this region. Based on recent findings, we hypothesize that the runt-related transcription factor 2 (RUNX2) may be a reasonable candidate gene for craniosynostosis in such patients.