Clinical segmentation in 22q11.2 deletion syndrome: Cognitive impairments and additional genetic load.

The 22q11.2 deletion syndrome (22q11.2DS) is associated with high psychiatric morbidity. However, large phenotypic heterogeneity hampers early detection of 22q11.2DS individuals at highest risk. Here, we investigated whether individuals with 22q11.2DS can be subdivided into clinically relevant subgroups based on their severity of cognitive impairments and whether such subgroups differ in polygenic risk. Using a cross-sectional design, we examined the number of lifetime psychiatric diagnoses and polygenic risk scores for schizophrenia in an unselected nationwide biobank cohort of individuals with 22q11.2DS (n = 183). Approximately 35% of this sample, aged 10-30 years, had a history with one or more psychiatric diagnosis. In a representative nested subgroup of 28 children and youth, we performed additional comprehensive cognitive evaluation and assessed psychiatric symptoms. Unsupervised hierarchical cluster analysis was performed to divide the subgroup of 22q11.2DS individuals, based on their performance on the cognitive testing battery. This produced two groups that did not differ in mean age or gender composition, but were characterized by low cognitive (LF) and high cognitive (HF) functional levels. The LF group, which had significantly lower global cognitive functioning scores, also displayed higher negative symptom scores; whereas, the HF group displayed lower rate of current psychiatric disorders than the LF group and the reminder of the biobank cohort. The polygenic risk score for schizophrenia was insignificantly lower for the low functioning group than for the high functioning group, after adjustment. Cognitive functioning may provide useful information on psychiatric risk.

Clinical presentations of 23 half-siblings from a mosaic neurofibromatosis type 1 sperm donor.

The Danish sperm donor number 7042 has fathered several offspring with neurofibromatosis type 1 (NF1) worldwide. NF1 is caused by loss-of-function mutations in the NF1 gene and more than 1000 NF1 mutations are identified. Analysis of the donor sperm demonstrated gonosomal mosaicism with an intragenic deletion involving exons 15-29 in the NF1 gene. At the two Danish reference centres for NF1 patients, we evaluated 23 half-siblings from the donor. Nine were diagnosed with NF1. The severity grade of NF1 progressed from minimal to mild/moderate within 3 years of follow-up. The NF1 phenotype shows great variability in intra- and inter-family expressivity and to date only two NF1 genotype-phenotype correlations have been established. This rare possibility of a long-term follow-up of a cohort of half-siblings with NF1 makes further studies including phenotypic variability and search for modifier genes possible. To achieve this goal, we have initiated The International Donor 7042 NF1 Offspring Registry. Research facilitated via this registry may reveal important new knowledge of clinical characteristics and prognostics for the specific NF1 genotype and thereby contribute to future individualised targeted clinical follow-up and treatment.

Gonosomal mosaicism for an NF1 deletion in a sperm donor: evidence of the need for coordinated, long-term communication of health information among relevant parties.

BACKGROUND: Screening of gamete donors can reduce but cannot eliminate the risks for medical problems in donor-conceived offspring. We present a case of gonosomal mosaicism discovered in an anonymous sperm donor after receiving two reports of neurofibromatosis type 1 (NF1) in donor-conceived offspring, to illustrate that long-term, systematic investigation of health issues in donors and offspring can be invaluable to the welfare of these individuals. METHODS: A repeat physical evaluation and ophthalmology examination were performed on the donor. DNA samples were examined by RTPCR fragment analysis, multiplex ligation-dependent probe amplification (MLPA) and targeted array-comparative genomic hybridization (aCGH). RESULTS: Gonosomal mosaicism for a deletion mutation in the NF1 gene was identified in 20% of sperm and a smaller percentage of lymphocytes. CONCLUSIONS: Long-term communication of medical information among donors, recipients and donor-conceived offspring is beneficial for the health management of all parties. Development of a secure, coordinated data system is critical to achieving this goal. Recommendations are provided for management and communication of critical information based on this experience.

FGFR3 mutations and the skin: report of a patient with a FGFR3 gene mutation, acanthosis nigricans, hypochondroplasia and hyperinsulinemia and review of the literature.

Fibroblast growth factor receptor 3 (FGFR3) gene mutations in the germline are well-known causes of skeletal syndromes. Somatic FGFR3 mutations have been found in malignant neoplasms and more recently in several cutaneous elements. We present a 14-year-old girl with mild hypochondroplasia who developed acanthosis nigricans. The report of a K650Q mutation in the FGFR3 gene in a similar case prompted us to conduct a point mutation analysis. The K650Q mutation was confirmed, but in contrast to the previous case, we additionally report findings of hyperinsulinemia. In the recent literature, an increasing number of different cutaneous elements have been found to harbor mutations of FGFR3, suggesting that FGFR3 plays a role in the pathogenesis of these elements. We review the present literature, describing studies in which FGFR3 mutations have been investigated in skin lesions: primarily seborrheic keratoses and epidermal nevi, but also other benign skin tumors and a single case of a squamous cell carcinoma. In addition, an overview of the FGFR3 point mutations in relation to each cutaneous element is given. Based on the current knowledge, it seems likely that these cutaneous lesions have a common genetic background. Our case shows that FGFR3 mutation analysis should be considered in case of the coexistence of acanthosis nigricans and a skeletal dysplasia. Testing for hyperinsulinemia is essential, also if a gene mutation is confirmed.

Phenotypic variability in 49 cases of ESCO2 mutations, including novel missense and codon deletion in the acetyltransferase domain, correlates with ESCO2 expression and establishes the clinical criteria for Roberts syndrome.

BACKGROUND: Roberts syndrome (RBS) and SC phocomelia are caused by mutations in ESCO2, which codes for an acetyltransferase involved in the regulation of sister chromatid cohesion. Of 26 mutations described to date, only one missense mutation has been reported and all others are predicted to be truncating mutations. Genotype-phenotype analysis has been hampered by limited numbers of patients with clinical information available. OBJECTIVE: To provide unpublished clinical data for 31 patients with proven ESCO2 mutations and combine this series with previously reported clinical and mutation data on 18 cases. Methods Genotype-phenotype correlations and functional effects of two novel ESCO2 mutations were analysed. In situ hybridisation on human embryos at Carnegie stages 14, 17 and 21 was performed to study ESCO2 expression during development. RESULTS AND CONCLUSIONS: Using the cohort of 49 patients, the clinical criteria for RBS were delineated to include: growth retardation; symmetric mesomelic shortening of the limbs in which the upper limbs are more commonly and severely affected than the lower limbs; characteristic facies with microcephaly. The severity of malformations of the facies correlates with the severity of limb reduction. The occurrence of corneal opacities may be associated with specific mutations. Two new mutations, both in the ESCO2 acetyltransferase domain, are described and their acetylation effects in vitro demonstrated. In situ hybridisation on human embryos showed ESCO2 expression in the brain, face, limb, kidney and gonads, which corresponds to the structures affected in RBS.

Ventricular tachycardia in a Brugada syndrome patient caused by a novel deletion in SCN5A.

The aim of the present study was to identify the molecular mechanism behind ventricular tachycardia in a patient with Brugada syndrome. Arrhythmias in patients with Brugada syndrome often occur during sleep. However, a 28-year-old man with no previously documented arrhythmia or syncope who experienced shortness of breath and chest pain during agitation is described. An electrocardiogram revealed monomorphic ventricular tachycardia; after he was converted to nodal rhythm, he spontaneously went into sinus rhythm, and showed classic Brugada changes with coved ST elevation in leads V(1) to V(2). Mutation analysis of SCN5A revealed a novel mutation, 3480 deletion T frame shift mutation, resulting in premature truncation of the protein. Heterologous expression of this truncated protein in human embryonic kidney 293 cells showed a markedly reduced protein expression level. By performing whole-cell patch clamp experiments using human embryonic kidney 293 cells transfected with the mutated SCN5A, no current could be recorded. Hence, the results suggest that the patient suffered from haploinsufficiency of Na(v)1.5, and that this mutation was the cause of his Brugada syndrome.

Leukocyte cDNA analysis of NSD1 derived from confirmed Sotos syndrome patients.

BACKGROUND: Haploinsufficiency of the NSD1 gene leads to Sotos syndrome (Sos), which is characterised by excessive growth, especially during childhood, distinct craniofacial features and variable degree of mental impairment. A wide spectrum of NSD1 mutations have been described in Sos patients, ranging from more than 100 different single nucleotide changes, to partial gene deletions, and to microdeletions of various sizes comprising the entire NSD1 locus. OBJECTIVE: To investigate the NSD1 cDNA sequence in genetically confirmed Sos patients harbouring truncating and missense mutations. METHOD: Total RNA was isolated from a 250 mul standard EDTA blood sample from nine genetically verified Sos patients, and subsequent reverse-transcribed into cDNA followed by PCR and direct sequencing of specific NSD1 cDNA sequences. RESULTS: All nine mutations, including missense, nonsense and whole exon deletions, previously identified in genomic DNA, could confidently be detected in cDNA. Several NSD1 transcript splice variants were detected. CONCLUSION: Despite the fact that Sos is caused by haploinsufficiency, NSD1 transcripts containing nonsense and frame shift mutations can be detected in leukocyte-derived cDNA. The possibility therefore exists that certain NSD1 mutations are expressed and contribute to the phenotypic variability of Sos. NSD1 cDNA analysis is likely to enhance mutation detection in Sos patients.

Carnitine transporter and holocarboxylase synthetase deficiencies in The Faroe Islands.

Carnitine transporter deficiency (CTD) and holocarboxylase synthetase deficiency (HLCSD) are frequent in The Faroe Islands compared to other areas, and treatment is available for both disorders. In order to evaluate the feasibility of neonatal screening in The Faroe Islands we studied detection in the neonatal period by tandem mass spectrometry, carrier frequencies, clinical manifestations, and effect of treatment of CTD and HLCSD. We found 11 patients with CTD from five families and 8 patients with HLCSD from five families. The natural history of both disorders varied extensively among patients, ranging from patients who presumably had died from their disease to asymptomatic individuals. All symptomatic patients responded favourably to supplementation with L: -carnitine (in case of CTD) or biotin (in case of HLCSD), but only if treated early. Estimates of carrier frequency of about 1:20 for both disorders indicate that some enzyme-deficient individuals remain undiagnosed. Prospective and retrospective tandem mass spectrometry (MS/MS) analyses of carnitines from neonatally obtained filter-paper dried blood-spot samples (DBSS) uncovered 8 of 10 individuals with CTD when using both C(0) and C(2) as markers (current algorithm) and 10 of 10 when using only C(0) as marker. MS/MS analysis uncovered 5 of 6 patient with HLCSD. This is the first study to report successful neonatal MS/MS analysis for the diagnosis of HLCSD. We conclude that CTD and HLCSD are relatively frequent in The Faroe Islands and are associated with variable clinical manifestations, and that diagnosis by neonatal screening followed by early therapy will secure a good outcome.

Xanthurenic aciduria due to a mutation in KYNU encoding kynureninase.

Massive urinary excretion of xanthurenic acid, 3-hydroxykynurenine and kynurenine, known as xanthurenic aciduria or hydroxykynureninuria, in a young Somali boy suggested kynureninase deficiency. Mutation analysis of KYNU encoding kynureninase of the index case revealed homozygosity for a c.593 A > G substitution leading to a threonine-to-alanine (T198A) shift. A younger brother was found to have a similar excretion pattern and the same genotype. At present, neither of the two boys has symptoms of niacin deficiency. This is the first report linking xanthurenic aciduria to a mutation in the gene encoding kynureninase.