Familial Kleefstra syndrome due to maternal somatic mosaicism for interstitial 9q34.3 microdeletions.

The Kleefstra syndrome (Online Mendelian Inheritance in Man 607001) is caused by a submicroscopic 9q34.3 deletion or by intragenic euchromatin histone methyl transferase 1 (EHMT1) mutations. So far only de novo occurrence of mutations has been reported, whereas 9q34.3 deletions can be either de novo or caused by complex chromosomal rearrangements or translocations. Here we give the first descriptions of affected parent-to-child transmission of Kleefstra syndrome caused by small interstitial deletions, approximately 200 kb, involving part of the EHMT1 gene. Additional genome-wide array studies in the parents showed the presence of similar deletions in both mothers who only had mild learning difficulties and minor facial characteristics suggesting either variable clinical expression or somatic mosaicism for these deletions. Further studies showed only one of the maternal deletions resulted in significantly quantitative differences in signal intensity on the array between the mother and her child. But by investigating different tissues with additional fluorescent in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) analyses, we confirmed somatic mosaicism in both mothers. Careful clinical and cytogenetic assessments of parents of an affected proband with an (interstitial) 9q34.3 microdeletion are merited for accurate estimation of recurrence risk.

Genetic screening for nevoid basal cell carcinoma syndrome in patients with a solitary keratocystic odontogenic tumour is not useful.

AIM: The aim of this study was to investigate the need for routine genetic counselling for identification of features of nevoid basal cell carcinoma syndrome (NBCCS) in patients presenting with a solitairy keratocystic odontogenic tumour (KCOT) of the jaws. METHODS: Sixty-nine patients treated for a solitary KCOT have been followed for the possible development of second KCOTs or other signs indicative of NBCCS. In addition, 11 randomly selected patients of this group were referred for genetic counselling, including identification of germ-line mutations in the Patched gene (PTCH gene). RESULTS: In none of the 69 patients clinical and radiographic manifestations of second KCOTs and/or other features associated with NBCCS were found during a follow-up period of 49.8 months. In the 11 patients referred for genetic counselling, there were no features indicative of the presence of NBCCS. No mutations in the PTCH gene could be identified. CONCLUSION: This study does not support the need for routine genetic counselling in patients presenting with a solitairy keratocystic odontogenic tumour of the jaws.

Two cases of severe neonatal hypertrophic cardiomyopathy caused by compound heterozygous mutations in the MYBPC3 gene.

BACKGROUND: Idiopathic (primary) hypertrophic cardiomyopathy (HCM) is mainly caused by mutations in genes encoding sarcomeric proteins. One of the most commonly mutated HCM genes is the myosin binding protein C (MYBPC3) gene. Mutations in this gene lead mainly to truncation of the protein which gives rise to a relatively mild phenotype. Pure HCM in neonates is rare and most of the time childhood HCM occurs in association with another underlying condition. OBJECTIVE: To study the presence of mutations in the MYBPC3 gene in idiopathic childhood HCM. METHODS: MYBPC3 coding region and splice junction variation were analysed by denaturing high performance liquid chromatography (DHPLC) and sequencing in DNA isolated from two neonates with severe unexplained HCM, who died within the first weeks of life. RESULTS: Truncating mutations were found in both alleles of the MYBPC3 gene in both patients, suggesting there was no functional copy of the MYBPC3 protein. Patient 1 carried the maternally inherited c.2373_2374insG mutation and the paternally inherited splice-donor site mutation c.1624+1G-->A. Patient 2 carried the maternally inherited frameshift mutation c.3288delA (p.Glu1096fsX92) and the paternally inherited non-sense mutation c.2827C-->T (p.Arg943X). CONCLUSIONS: The findings indicate the need for mutation analysis of genes encoding sarcomeric proteins in childhood HCM and the possibility of compound heterozygosity.

CHARGE syndrome: the phenotypic spectrum of mutations in the CHD7 gene.

BACKGROUND: CHARGE syndrome is a non-random clustering of congenital anomalies including coloboma, heart defects, choanal atresia, retarded growth and development, genital hypoplasia, ear anomalies, and deafness. A consistent feature in CHARGE syndrome is semicircular canal hypoplasia resulting in vestibular areflexia. Other commonly associated congenital anomalies are facial nerve palsy, cleft lip/palate, and tracheo-oesophageal fistula. Specific behavioural problems, including autistic-like behaviour, have been described. The CHD7 gene on chromosome 8q12.1 was recently discovered as a major gene involved in the aetiology of this syndrome. METHODS: The coding regions of CHD7 were screened for mutations in 107 index patients with clinical features suggestive of CHARGE syndrome. Clinical data of the mutation positive patients were sampled to study the phenotypic spectrum of mutations in the CHD7 gene. RESULTS: Mutations were identified in 69 patients. Here we describe the clinical features of 47 of these patients, including two sib pairs. Most mutations were unique and were scattered throughout the gene. All patients but one fulfilled the current diagnostic criteria for CHARGE syndrome. No genotype-phenotype correlations were apparent in this cohort, which is best demonstrated by the differences in clinical presentation in sib pairs with identical mutations. Somatic mosaicism was detected in the unaffected mother of a sib pair, supporting the existence of germline mosaicism. CONCLUSIONS: CHD7 mutations account for the majority of the cases with CHARGE syndrome, with a broad clinical variability and without an obvious genotype-phenotype correlation. In one case evidence for germline mosaicism was provided.

[From gene to disease; EVC, EVC2, and Ellis-van Creveld syndrome]. / Van gen naar ziekte; EVC, EVC2 en Ellis-van Creveld-syndroom.

Ellis-van Creveld syndrome is an autosomal recessive disorder characterised by short stature with short limbs, postaxial polydactyly and congenital cardiac defects. The syndrome can be caused by mutations in the EVC gene or the EVC2 gene. The genes are located close to each other in a head-to-head configuration on chromosome 4p16. Clinical diagnosis can be confirmed by DNA analysis, which is currently offered by two laboratories in Italy.

[Restrictive dermopathy: a rare, lethal genodermatosis]. / Restrictieve dermopathie: een zeldzame, letale genodermatose.

In a premature male infant born of consanguineous parents, restrictive dermopathy was diagnosed. This is a rarely described, lethal, congenital skin disease. The diagnosis was based on the clinical and histopathological findings: a fixed facial expression (so-called 'porcelain face') with palpebral fissures inclined laterally downwards, microstomia with the mouth in the 'O'-position, micrognathia and low-set ears inclined toward the rear, prominent blood vessels in the skin and contracture of all the joints; histopathological examination of a skin biopsy revealed a smooth epidermis and a relatively thin dermis with an abnormal structure of the dermal connective tissue in which the collagen fibres were arranged more or less horizontally, parallel to the epidermis, and the number of elastin fibres was sharply decreased. Various adnexal structures were present but the hair follicles had an abortive appearance. Thanks in part to the finding of a homozygous mutation in the so-called ZMPSTE24-gene, it could be concluded that restrictive dermopathy is probably an autosomal recessive laminopathy, related to progeria. Increasing the clinical awareness of this disease may contribute to reducing the presumed under-reporting, so that future research will become possible.

[From gene to disease: basal cell naevus syndrome]. / Van gen naar ziekte; basaalcelnaevussyndroom.

Nevoid basal cell carcinoma syndrome (NBCCS, basal cell naevus syndrome, Gorlin syndrome) is an autosomal dominant disorder, caused by mutations in the PTCH gene mapped to chromosome 9q22.3. It is characterised by multiple basal cell carcinomas, keratocysts of the jaws, palmar and plantar pits, cerebral ectopic calcification and several skeletal anomalies. Occasionally, patients with NBCCS develop other neoplasms, particularly medulloblastomas and ovarian fibromas, indicating that the PTCH gene is a tumor-suppressor gene. Early recognition and careful follow-up are needed. Guidelines for managing these patients are presented.

Saccade dysmetria in Williams-Beuren syndrome.

Numerous studies have described the poor visuo-spatial processing capacities of subjects with Williams-Beuren syndrome (WBS), a genetically based developmental disorder. Since visual perception and eye movements are closely related we hypothesized that the poor visuo-spatial processing capacities of subjects with WBS might be related to a poor saccadic control. Thereto, we recorded horizontal and vertical saccadic eye movements to targets using infrared video-oculography in 27 subjects with WBS and eight healthy controls. In the WBS group saccadic gains were highly variable, both between and within individual subjects, and they often needed more than one correction saccade to reach the target. Ten (out of a subgroup of 22) WBS subjects showed a large number of hypometric and/or hypermetric saccades, and, also a left-right asymmetry in saccadic gains was observed in WBS. We conclude that the observed impairments in saccadic control are likely to affect the proper processing of visuo-spatial information.

Kabuki syndrome in son and low grade mosaic 45,X/46,XX in mother.

We report on a two-year-old boy with Kabuk syndrome and a normal male karyotype whose mother is a low grade mosaic 45,X/46,XX. We hypothesized that the son's Kabuki syndrome might have been caused by gonosomal uniparental (paternal) disomy DNA analysis proved this hypothesis to be incorrect. A review of twelve patients with Kabuki syndrome or Kabuki-syndrome-like features and chromosome abnormalities is presented.

[Williams syndrome: new insights into genetic etiology, pathogenesis and clinical aspects]. / Williams-syndroom: nieuwe inzichten in genetische etiologie, pathogenese en kliniek.

Williams syndrome (WS) is a developmental disorder characterized by distinct facial features, congenital heart disease, mental retardation and a gregarious personality. The majority of people with this disorder have a submicroscopic deletion of genes in chromosome band 7q11.23. This deletion can be detected using fluorescence in situ hybridization (FISH). Although the condition is usually sporadic a few familial cases with autosomal dominant inheritance have been described. A clinical scoring system has been developed by Selicorni with which a diagnosis of 'Williams syndrome' can be made; in all patients in whom the diagnosis was made in this way FISH results were positive.

[Syndromes 18. Von Recklinghausen's disease]. / Syndromen 18. De ziekte van Von Recklinghausen.

Von Recklinghausen's disease (neurofibromatosis 1; NF1) is one of the neurofibromatoses and accounts for about 90% of all cases. Inheritance is autosomal dominant with about 30-50% of cases representing new mutations. Characteristic features for NF1 are six or more café-au-lait-spots, neurofibromas, Lisch nodules and axillary freckling. Oral manifestation consists of neurofibromas and intrabony lesions. Due to growth of the oral and facial neurofibromas maldevelopment of the facial skeleton and malocclusion are seen. Surgical correction in young individuals easily leads to recurrence. Contour corrected surgery in grown up individuals is possible.

[Syndromes 21: Ellis-Van Creveld syndrome]. / Syndromen 21. Het syndroom van Ellis-Van Creveld.

Patients with the Ellis-Van Creveld syndrome have a short stature. The extremities are often plump and markedly shortened, progressively from the trunk to the fingers and the toes. A bilateral postaxial sixth finger is frequent. The most striking and consistent finding in the mouth is fusion of the middle part of the upper lip to the labial sulcus, resulting in a so-called 'whistling deformity'. Congenitally missing teeth, particularly in the frontal region, are a constant finding too. Teeth are usually small and have conical crowns. Supernummer teeth have also been noted. The oral and maxillofacial surgeon will treat the hypertrophic upper frenulum; the dentist will treat the oligodontia of the frontal region and the conical crowns by means of laminated veneers and etch composite bridgework.

[Syndromes 17. Hypohidrotic ectodermal dysplasia]. / Syndromen 17. Hypohidrotische ectodermale dysplasie.

The X-linked hypohidrotic ectodermal dysplasia (HED) is characterized by hypohidrosis, hypotrichosis and hypodontia. Sebaceous and salivary glands ar also affected. Recognition of the syndrome usually comes from affected man, although female carriers may show symptoms. Dental treatment is complicated and should be coordinated by a dentist in a centre for special dental care. Cooperation with an orthodontist and an oral and maxillofacial surgeon is advocated.

[Syndromes 14. Rendu-Osler-Weber disease]. / Syndromen 14. De ziekte van Rendu-Osler-Weber.

The Rendu-Osler-Weber disease is due to an autosomal dominant disease with multiple telangiectasia in skin and mucosa. Recurrent bleeding of the nose is due to telangiectasia of the nasal mucosa. Haemorrhage of the oral mucosa also occurs. Extensive arteriovenous malformations can be present in lungs, liver and brain. Treatment of bleedings in the oral mucosa is easily possible by means of coagulation. Patients with pulmonary arteriovenous malformations should receive prophylactic antibiotic treatment before extractions, removal of third molars and subgingival curettage.

[Syndromes 5. Williams-Beuren Syndrome]. / Syndromen 5. Het Williams-Beuren-syndroom.

A characteristic facial appearance, mental retardation, growth deficiency, cardiovascular anomalies, and infantile hypercalcemia are major features of the Williams-Beuren syndrome. The dentist can contribute to the (early) diagnosis of this disorder.

[Syndromes 22. Rieger's syndrome]. / Syndromen 22. Het syndroom van Rieger.

Rieger syndrome is a rare autosomal-dominant disorder characterized by defects of the anterior chamber of the eye, failure of the periumbilical skin to involute, and developmental malformations of the dentition. Recognition of the dental anomalies may result in the early diagnosis of this syndrome and prevent progressive visual loss.

Germline Mutations in RASA1 Are Not Found in Patients with Klippel-Trenaunay Syndrome or Capillary Malformation with Limb Overgrowth.

The RASA1 gene encodes p120RASGAP, a multidomain cytoplasmic protein that acts as a negative regulator of the RAS signalling pathway. Heterozygous loss-of-function RASA1 mutations were identified in patients with Parkes Weber syndrome and multifocal capillary malformations. This syndrome is characterised by a capillary blush on an extremity, arteriovenous microfistulas, and bony and soft tissue hypertrophy. The aim of this study was to test RASA1 in 2 disorders characterised by asymmetric limb enlargement and vascular malformations, namely Klippel-Trenaunay syndrome and regional capillary malformation with overgrowth. We did not identify any clear pathogenic change in these patients. Thus, besides clinical and radiological criteria, RASA1 testing constitutes an additional tool to differentiate Parkes Weber syndrome of capillary malformation-arteriovenous malformation (CM-AVM) from overlapping disorders.

[A neonate with a congenital hand defect]. / Een neonaat met een aangeboren handafwijking.

A newborn presented with a birth defect of his left hand and unilateral hypoplasia of his left musculus pectoralis major and left nipple. He was diagnosed with Poland syndrome.