Kathelijn Keymolen

The annual incidence of DiGeorge/velocardiofacial syndrome.

1 Boughman JA, Conneally PM, Nance WE. Population genetic studies of retinitis pigmentosa. AmJHum Genet 1980;32:223-35. 2 Inglehearn CF. Molecular genetics of inherited retinal dystrophies. Eye 1998;12:571-9. N 3 Sung CH, Davenport CM, Hennessey JC, et al. Rhodopsin mutations in autosomal dominant retinitis pigmentosa. Proc Natl Acad Sci USA 199 1;88:6481-5. 4 Inglehearn CF, Tarttelin EE, Plant C, et al. A genetic survey oftwenty dominant retinitis pigs mentosa families: frequencies of the eight known loci and evidence for further heterogeneity.J Med Genet 1998;35:1-5. 5 Souied EH, Rozet JM, Gerber S, et al. Screening for mutations within the rhodopsin, peripherin-RDS and ROMI genes in auto-

The mutation spectrum in RECQL4 diseases.

Mutations in the RECQL4 gene can lead to three clinical phenotypes with overlapping features. All these syndromes, Rothmund–Thomson (RTS), RAPADILINO and Baller–Gerold (BGS), are characterized by growth retardation and radial defects, but RAPADILINO syndrome lacks the main dermal manifestation, poikiloderma that is a hallmark feature in both RTS and BGS. It has been previously shown that RTS patients with RECQL4 mutations are at increased risk of osteosarcoma, but the precise incidence of cancer in RAPADILINO and BGS has not been determined. Here, we report that RAPADILINO patients identified as carriers of the c.1390+2delT mutation (p.Ala420_Ala463del) are at increased risk to develop lymphoma or osteosarcoma (6 out of 15 patients). We also summarize all the published RECQL4 mutations and their associated cancer cases and provide an update of 14 novel RECQL4 mutations with accompanying clinical data.

Phenotype and 244k array-CGH characterization of chromosome 13q deletions: An update of the phenotypic map of 13q21.1-qter†

Partial deletions of the long arm of chromosome 13 lead to variable phenotypes dependant on the size and position of the deleted region. In order to update the phenotypic map of chromosome 13q21.1‐qter deletions, we applied 244k Agilent oligonucleotide‐based array‐CGH to determine the exact breakpoints in 14 patients with partial deletions of this region. Subsequently, we linked the genotype to the patients phenotype. Using this approach, we were able to refine the smallest deletion region linked to short stature (13q31.3: 89.5–91.6 Mb), microcephaly (13q33.3–q34), cortical development malformations (13q33.1‐qter), Dandy–Walker malformation (DWM) (13q32.2–q33.1), corpus callosum agenesis (CCA) (13q32.3–q33.1), meningocele/encephalocele (13q31.3‐qter), DWM, CCA, and neural tube defects (NTDs) taken together (13q32.3–q33.1), ano‐/microphthalmia (13q31.3–13qter), cleft lip/palate (13q31.3–13q33.1), lung hypoplasia (13q31.3–13q33.1), and thumb a‐/hypoplasia (13q31.3–q33.1 and 13q33.3–q34). Based on observations of this study and previous reports we suggest a new entity, “distal limb anomalies association,” linked to 13q31.3q33.1 segment. Most of the individuals with deletion of any part of 13q21qter showed surprisingly similar facial dysmorphic features, and thus, a “13q deletion facial appearance” was suggested. Prominent nasal columella was mapped between 13q31.3 and 13q33.3, and micrognathia between 13q21.33 and 13q31.1. The degree of mental delay did not display a particular phenotype–genotype correlation on chromosome 13. In contrast to previous reports of carriers of 13q32 band deletions as the most seriously affected patients, we present two such individuals with long‐term survival, 28 and 2.5 years.

A common mutation in the COG7 gene with a consistent phenotype including microcephaly, adducted thumbs, growth retardation, VSD and episodes of hyperthermia

We describe the clinical and biochemical characteristics in three patients from two different families diagnosed with Congenital Disorder of Glycosylation type IIe owing to a defect in Conserved Oligomeric Golgi complex (COG)7; one of the eight subunits of the COG. The siblings and an unrelated single child of consanguineous parents presented with growth retardation, progressive, severe microcephaly, hypotonia, adducted thumbs, feeding problems by gastrointestinal pseudo-obstruction, failure to thrive, cardiac anomalies, wrinkled skin and episodes of extreme hyperthermia. A combined disorder in the biosynthesis of N- and O-linked glycosylation with hyposialylation was detected. Western blot analysis showed a severe reduction in the COG5 and 7 subunits of the COG. A homozygous, intronic splice site mutation (c.169+4A>C) of the COG7 gene was identified in all patients. The phenotype is similar to that previously described in two patients of North African ethnicity with the same mutation, except for the lack of skeletal anomalies and only a mild liver involvement in our patients. We suggest performing protein glycosylation studies and Western blot for the different COG subunits in patients with progressive microcephaly, growth retardation, hypotonia, adducted thumbs and cardiac defects, especially in association with skin anomalies or episodes of hyperthermia. The presence of the characteristic phenotype might warrant direct DNA analysis.

The nutritional value of a whey hydrolysate formula compared with a whey-predominant formula in healthy infants

Forty-five healthy infants were included in a double-blind randomized prospective study comparing the nutritional value of two formulas. One group received a whey-predominant formula (n = 20); the other group received a whey hydrolysate formula (n = 25). Four infants of the whey hydrolysate group were dropped because they refused the formula. Although the mean daily volume intake was smaller with the whey hydrolysate formula compared with the whey-predominant formula (p < 0.001), the weight gain in the two groups after 13 weeks was identical (27.2 g/day in both groups; the mean difference in weight gain between the groups after 13 weeks was only 8 g). Length gain at 13 weeks was 10.4 cm in the whey-predominant formula group and 10.8 cm in the whey hydrolysate formula group (p = NS). After 13 weeks, blood was sampled for hemoglobin, hematocrit, red blood cell count, white blood cell count, lymphocytes, glycemia, proteins, albumin, prealbumin, calcium, phosphorus, urea, creatinine, iron, iron-binding capacity, zinc, and vitamins A and E. Except for the iron-binding capacity, zinc, urea (in plasma as well as in urine) (all three were higher in the whey hydrolysate group), no significant differences were found. According to these results, exclusive feeding of the whey hydrolysate formula from birth to 3 months of age to healthy infants appears to result in an adequate nutritional status, as assessed at 3 months of age.

Early onset Huntington disease: a neuronal degeneration syndrome.

Huntington disease (HD) is an autosomal dominant, lethal neurodegenerative disorder of the central nervous system, caused by an uncontrolled expansion of a CAG dynamic mutation in the coding region of the IT15gene. Although a majority of patients have a midlife onset of the disease, in a small number of patients the disease manifests before 20 years of age. In adults, HD is mainly characterised by involuntary movements, personality changes and dementia. By contrast, in children a dominant picture of bradykinesia, rigidity, dystonia and epileptic seizures is noticed. The earlier onset is often associated with a paternal transmission of the disease allele to the offspring. We report here a rather unusual infantile onset of the disease in a little girl who presented with a history of seizures and psychomotor regression starting at the age of 3 years. A progressive cortical-subcortical atrophy, progressive cerebellar atrophy and lesions in the basal ganglia were found on MRI. An important expansion, of 214 triplet numbers, of the CAG repeat size associated with HD, was observed. Conclusion:Juvenile Huntingdon disease should be considered in children suffering from a progressive neurodegenerative disease.

Implementation of genomic arrays in prenatal diagnosis: The Belgian approach to meet the challenges

After their successful introduction in postnatal testing, genome-wide arrays are now rapidly replacing conventional karyotyping in prenatal diagnostics. While previous studies have demonstrated the advantages of this method, we are confronted with difficulties regarding the technology and the ethical dilemmas inherent to genomic arrays. These include indication for testing, array design, interpretation of variants and how to deal with variants of unknown significance and incidental findings. The experiences with these issues reported in the literature are most often from single centres. Here, we report on a national consensus approach how microarray is implemented in all genetic centres in Belgium. These recommendations are subjected to constant re-evaluation based on our growing experience and can serve as a useful tool for those involved in prenatal diagnosis.

A prospective study of the clinical utility of prenatal chromosomal microarray analysis in fetuses with ultrasound abnormalities and an exploration of a framework for reporting unclassified variants and risk factors

Purpose:To evaluate the clinical utility of chromosomal microarrays for prenatal diagnosis by a prospective study of fetuses with abnormalities detected on ultrasound.Methods:Patients referred for prenatal diagnosis due to ultrasound anomalies underwent analysis by array comparative genomic hybridization as the first-tier diagnostic test.Results:A total of 383 prenatal samples underwent analysis by array comparative genomic hybridization. Array analysis revealed causal imbalances in a total of 9.6% of patients (n = 37). Submicroscopic copy-number variations were detected in 2.6% of patients (n = 10/37), and arrays added valuable information over conventional karyotyping in 3.9% of patients (n = 15/37). We highlight a novel advantage of arrays; a 500-kb paternal insertional translocation is the likely driver of a de novo unbalanced translocation, thus improving recurrence risk calculation in this family. Variants of uncertain significance were revealed in 1.6% of patients (n = 6/383).Conclusion:We demonstrate the added value of chromosomal microarrays for prenatal diagnosis in the presence of ultrasound anomalies. We advocate reporting back only copy-number variations with known pathogenic significance. Although this approach might be considered opposite to the ideal of full reproductive autonomy of the parents, we argue why providing all information to parents may result in a false sense of autonomy.Genet Med 16 6, 469–476.

TUBA1A mutations From isolated lissencephaly to familial polymicrogyria

Background: Mutations in the TUBA1A gene have been reported in patients with lissencephaly and perisylvian pachygyria. Methods: Twenty-five patients with malformations of cortical development ranging from lissencephaly to polymicrogyria were screened for mutations in TUBA1A. Results: Two novel heterozygous missense mutations in TUBA1A were identified: c.629A>G (p.Tyr210Cys) occurring de novo in a boy with lissencephaly, and c.13A>C (p.Ile5Leu) affecting 2 sisters with polymicrogyria whose mother presented somatic mosaicism for the mutation. Conclusions: Mutations in TUBA1A have been described in patients with lissencephaly and pachygyria. We report a mutation in TUBA1A as a cause of polymicrogyria. So far, all mutations in TUBA1A have occurred de novo, resulting in isolated cases. This article describes familial recurrence of TUBA1A mutations due to somatic mosaicism in a parent. These findings broaden the phenotypic spectrum associated with TUBA1A mutations and have implications for genetic counseling.

Legius syndrome in fourteen families

Legius syndrome presents as an autosomal dominant condition characterized by café‐au‐lait macules with or without freckling and sometimes a Noonan‐like appearance and/or learning difficulties. It is caused by germline loss‐of‐function SPRED1 mutations and is a member of the RAS‐MAPK pathway syndromes. Most mutations result in a truncated protein and only a few inactivating missense mutations have been reported. Since only a limited number of patients has been reported up until now, the full clinical and mutational spectrum is still unknown. We report mutation data and clinical details in fourteen new families with Legius syndrome. Six novel germline mutations are described. The Trp31Cys mutation is a new pathogenic SPRED1 missense mutation. Clinical details in the 14 families confirmed the absence of neurofibromas, and Lisch nodules, and the absence of a high prevalence of central nervous system tumors. We report white matter T2 hyperintensities on brain MRI scans in 2 patients and a potential association between postaxial polydactyly and Legius syndrome.