Pulmonary stenosis, café-au-lait spots, and dull intelligence

Speech and language skills in a case of Watson syndrome

Watson syndrome is a rare genetic condition partly characterised by developmental delays and learning difficulties. A profile of speech and language skills associated with this developmental syndrome is yet to be described in the literature. In order to address this gap, this study presents the case of an 18-year-old man with Watson syndrome and reports both standardised and naturalistic assessments of speech, language, oro-motor skills, and semantic and phonemic fluency. Analyses included norm-referencing, discrepancy comparison, phonological process analysis, and acoustic analyses of voice and conversational fluency. The participant's semantic fluency approximated to the 84th percentile and the vocabulary, voice, and receptive language measures were within standard normative range. In contrast, expressive language difficulties and articulatory difficulties associated with impaired oro-motor skills were apparent. Specific tongue-motor difficulty impeded oral diadochokinesis, with gliding, stopping, and cluster reduction among the phonological processes observed to mitigate oro-motor difficulties. Language scores were lowest on tasks of working memory, syntax, and pragmatics, however neither syntax nor pragmatics presented increased difficulty in naturalistic conversation, indicating an influence of reduced working memory on language performance. The absence of explicit cognitive or communicative difficulty suggests specific speech and language difficulties. To conclude, the findings are discussed from both clinical and theoretical perspectives. Watson syndrome and the aetiology of communication difficulties are suggested as directions for future research, to validate these findings and diversify understanding of inclusive communication approaches.

Neurofibromatosis Type 1: Pediatric Aspects and Review of Genotype-Phenotype Correlations

Neurofibromatosis type 1 (NF1) is an autosomal dominant condition, with a birth incidence of approximately 1:2000-3000, caused by germline pathogenic variants in NF1, a tumor suppressor gene encoding neurofibromin, a negative regulator of the RAS/MAPK pathway. This explains why NF1 is included in the group of RASopathies and shares several clinical features with Noonan syndrome. Here, we describe the main clinical characteristics and complications associated with NF1, particularly those occurring in pediatric age. NF1 has complete penetrance and shows wide inter- and intrafamilial phenotypic variability and age-dependent appearance of manifestations. Clinical presentation and history of NF1 are multisystemic and highly unpredictable, especially in the first years of life when penetrance is still incomplete. In this scenario of extreme phenotypic variability, some genotype-phenotype associations need to be taken into consideration, as they strongly impact on genetic counseling and prognostication of the disease. We provide a synthetic review, based on the most recent literature data, of all known genotype-phenotype correlations from a genetic and clinical perspective. Molecular diagnosis is fundamental for the confirmation of doubtful clinical diagnoses, especially in the light of recently revised diagnostic criteria, and for the early identification of genotypes, albeit few, that correlate with specific phenotypes.

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population.

Prevalence, Type, and Molecular Spectrum of NF1 Mutations in Patients with Neurofibromatosis Type 1 and Congenital Heart Disease

The aim of this study was to assess the prevalence and type of congenital heart disease (CHD) and the associated mutation spectrum in a large series of patients with neurofibromatosis type 1 (NF1), and correlate the mutation type with the presence and subgroups of cardiac defects. The study cohort included 493 individuals with molecularly confirmed diagnosis of NF1 for whom cardiac evaluation data were available. CHD was reported in 62/493 (12.6%) patients. Among these patients, 23/62 (37.1%) had pulmonary valve stenosis/dysplasia, 20/62 (32.3%) had mitral valve anomalies, and 10/62 (16.1%) had septal defects. Other defects occurred as rare events. In this NF1 subcohort, three subjects carried a whole-gene deletion, while 59 were heterozygous for an intragenic mutation. A significantly increased prevalence of non-truncating intragenic mutations was either observed in individuals with CHD (22/59, 37.3%) or with pulmonary valve stenosis (13/20, 65.0%), when compared to individuals without CHD (89/420, 21.2%) (p = 0.038) or pulmonary valve stenosis (98/459, 21.4%) (p = 0.002). Similarly, patients with non-truncating NF1 mutations displayed two- and six-fold higher risk of developing CHD (odds ratio = 1.9713, 95% confidence interval (CI): 1.1162-3.4814, p = 0.0193) and pulmonary valve stenosis (odds ratio = 6.8411, 95% CI: 2.6574-17.6114, p = 0.0001), respectively. Noteworthy, all but one patient (19/20, 95.0%) with pulmonary valve stenosis, and 18/35 (51.4%) patients with other CHDs displayed Noonan syndrome (NS)-like features. Present data confirm the significant frequency of CHD in patients with NF1, and provide further evidence for a higher than expected prevalence of NF1 in-frame variants and NS-like characteristics in NF1 patients with CHD, particularly with pulmonary valve stenosis.

Molecular screening strategies for NF1-like syndromes with café-au-lait macules (Review)

Multiple café-au-lait macules (CALM) are usually associated with neurofibromatosis type 1 (NF1), one of the most common hereditary disorders. However, a group of genetic disorders presenting with CALM have mutations that are involved in human skin pigmentation regulation signaling pathways, including KIT ligand/KIT proto‑oncogene receptor tyrosine kinase and Ras/mitogen‑activated protein kinase. These disorders, which include Legius syndrome, Noonan syndrome with multiple lentigines or LEOPARD syndrome, and familial progressive hyperpigmentation) are difficult to distinguish from NF1 at early stages, using skin appearance alone. Furthermore, certain syndromes are clinically overlapping and molecular testing is a vital diagnostic method. The present review aims to provide an overview of these 'NF1‑like' inherited diseases and recommend a cost‑effective strategy for making a clear diagnosis among these diseases with an ambiguous borderline.

Increased rate of missense/in-frame mutations in individuals with NF1-related pulmonary stenosis: a novel genotype-phenotype correlation

Neurofibromatosis type 1 (NF1) and its related disorders (NF1-Noonan syndrome (NFNS) and Watson syndrome (WS)) are caused by heterozygous mutations in the NF1 gene. Pulmonary stenosis (PS) occurs more commonly in NF1 and its related disorders than in the general population. This study investigated whether PS is associated with specific types of NF1 gene mutations in NF1, NFNS and WS. The frequency of different NF1 mutation types in a cohort of published and unpublished cases with NF1/NFNS/WS and PS was examined. Compared with NF1 in general, NFNS patients had higher rates of PS (9/35=26% vs 25/2322=1.1%, P value<0.001). Stratification according to mutation type showed that the increased PS rate appears to be driven by the NFNS group with non-truncating mutations. Eight of twelve (66.7%) NFNS cases with non-truncating mutations had PS compared with a 1.1% PS frequency in NF1 in general (P<0.001); there was no increase in the frequency of PS in NFNS patients with truncating mutations. Eight out of eleven (73%) individuals with NF1 and PS, were found to have non-truncating mutations, a much higher frequency than the 19% reported in NF1 cohorts (P<0.015). Only three cases of WS have been published with intragenic mutations, two of three had non-truncating mutations. Therefore, PS in NF1 and its related disorders is clearly associated with non-truncating mutations in the NF1 gene providing a new genotype-phenotype correlation. The data indicate a specific role of non-truncating mutations on the NF1 cardiac phenotype.

[Neuro-cardio-facial-cutaneous syndrome]

The concept of neuro-cardio-facio-cutaneous (NCFC) syndrome has recently been formulated in order to bring together a number of hereditary diseases that include a number of shared phenotypic features to differing degrees: (i) craniofacial dysmorphia; (ii) delayed growth; (iii) mental retardation or learning difficulties; (iv) cardiac malformations (most commonly pulmonary valve stenosis and hypertrophic cardiomyopathy); (v) cutaneous anomalies, and in some cases, predisposition to certain forms of malignant solid tumors and blood diseases, associated at the physiopathological level with deregulation of the Ras-MAP kinase cellular signaling pathways 1. NCFC subsumes neurofibromatosis type1, Legius syndrome, LEOPARD syndrome, Noonan syndrome, Costello syndrome and cardiofaciocutaneous (CFC) syndrome. While the majority of these diseases are readily distinguishable in clinical terms, with or without diagnostic criteria, none of them have any pathognomonic signs. Many cases attest to the strong clinical homologies and forms of overlapping between these different diseases. In recent years, the discovery of germinal mutations of these different diseases has in fact reinforced the unifying clinical and biochemical concept of NCFC syndrome.

Lethal presentation of neurofibromatosis and Noonan syndrome

Neurofibromatosis type 1 and Noonan syndrome are both common genetic disorders with autosomal dominant inheritance. Similarities between neurofibromatosis type 1 and Noonan syndrome have been noted for over 20 years and patients who share symptoms of both conditions are often given the diagnosis of neurofibromatosis-Noonan syndrome (NFNS). The molecular basis of these combined phenotypes was poorly understood and controversially discussed over several decades until the discovery that the syndromes are related through disturbances of the Ras pathway. We present an infant male with coarse facial features, severe supravalvar pulmonic stenosis, automated atrial tachycardia, hypertrophic cardiomyopathy, airway compression, severe neurological involvement, and multiple complications that lead to death during early infancy. The severity of clinical presentation and significant dysmorphic features suggested the possibility of a double genetic disorder in the Ras pathway instead of NFNS. Molecular analysis showed a missense mutation in exon 25 of the NF1 gene (4288A>G, p.N1430D) and a pathogenic mutation on exon 8 (922A>G, p.N308D) of the PTPN11 gene. Cardiovascular disease has been well described in patients with Noonan syndrome with PTPN11 mutations but the role of haploinsufficiency for neurofibromin in the heart development and function is not yet well understood. Our case suggests that a double genetic defect resulting in the hypersignaling of the Ras pathway may lead to complex cardiovascular abnormalities, cardiomyopathy, refractory arrhythmia, severe neurological phenotype, and early death.

Disorders of dysregulated signal traffic through the RAS-MAPK pathway: phenotypic spectrum and molecular mechanisms

RAS GTPases control a major signaling network implicated in several cellular functions, including cell fate determination, proliferation, survival, differentiation, migration, and senescence. Within this network, signal flow through the RAF-MEK-ERK pathway-the first identified mitogen-associated protein kinase (MAPK) cascade-mediates early and late developmental processes controlling morphology determination, organogenesis, synaptic plasticity, and growth. Signaling through the RAS-MAPK cascade is tightly controlled; and its enhanced activation represents a well-known event in oncogenesis. Unexpectedly, in the past few years, inherited dysregulation of this pathway has been recognized as the cause underlying a group of clinically related disorders sharing facial dysmorphism, cardiac defects, reduced postnatal growth, ectodermal anomalies, variable cognitive deficits, and susceptibility to certain malignancies as major features. These disorders are caused by heterozygosity for mutations in genes encoding RAS proteins, regulators of RAS function, modulators of RAS interaction with effectors, or downstream signal transducers. Here, we provide an overview of the phenotypic spectrum associated with germline mutations perturbing RAS-MAPK signaling, the unpredicted molecular mechanisms converging toward the dysregulation of this signaling cascade, and major genotype-phenotype correlations.

Neurofibromatosis type 1 with overlap Turner syndrome and Klinefelter syndrome

Turner's syndrome is a sex chromosome disorder. Klinefelter's syndrome is one of the most severe genetic diseases. Neurofibromatosis is an autosomal dominant disorder characterized by cafe-au-lait spots and fibromatous tumors of the skin. In this article, we report the overlap of neurofibromatosis-1 with Turner and Klinefelter syndromes. Thus, these disorders might overlap within the same patient. Due to these cases, we suggest that each patient with Turner-like symptoms or Klinefelter's-like syndrome, be carefully examined for café au lait macules before the initiation of hormone replacement treatment.

Neurofibromatosis type 1 in genetic counseling practice: recommendations of the National Society of Genetic Counselors

The objective of this document is to provide recommendations for the genetic counseling of patients and families undergoing evaluation for neurofibromatosis type 1 (NF1) or who have received a diagnosis of NF1. These recommendations are the opinions of a multi-center working group of genetic counselors with expertise in the care of individuals with NF1. These recommendations are based on the committee's clinical experiences, a review of pertinent English language medical articles, and reports of expert committees. These recommendations are not intended to dictate an exclusive course of management, nor does the use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of an individual patient.

Pulmonary Artery Aneurysm and Coronary Artery Disease in the Clinical Presentation of Watson Syndrome

In 1967, Watson described children in three families with pulmonary valve stenosis, dull intelligence, short stature, and cafe-au-lait spots. We present the case of an undiagnosed adult with coronary artery disease, the Watson syndrome characteristics, and a pulmonary artery aneurysm secondary to pulmonic stenosis.

Clinical and molecular aspects of an informative family with neurofibromatosis type 1 and Noonan phenotype

Neurofibromatosis-Noonan syndrome (NFNS) has been described as a unique phenotype, combining manifestations of neurofibromatosis type 1 (NF1) and Noonan syndrome, which are separate syndromes. Potential etiologies of NFNS include a discrete syndrome of distinct etiology, co-segregation of two mutated common genes, variable clinical expressivity of NF1, and/or allelic heterogeneity. We present an informative family with an unusual NF1 mutation with variable features of NF1 and Noonan syndrome. We hypothesize that an NF1 mutant allele can lead to diagnostic manifestations of Noonan syndrome, supporting the hypothesis that NF1 allelic heterogeneity causes NFNS.

A variable combination of features of Noonan syndrome and neurofibromatosis type I are caused by mutations in theNF1 gene

Signs of neurofibromatosis type 1 (NF1) and Noonan syndrome (NS), two distinct autosomal dominant disorders, occur together in patients reported as Watson syndrome (WS), neurofibromatosis-Noonan syndrome (NFNS), partial LEOPARD syndrome, NS with features of NF1, and NF1 with Noonan-like features. The molecular basis of these combined phenotypes was poorly understood and controversially discussed over several decades. Only recently, there is increasing evidence for WS and NFNS being allelic to NF1 in the majority of patients. In this study we describe seven novel patients from five unrelated families with variable phenotypes of the NF1-NS spectrum which were systematically analyzed for mutations in the disease-causing genes NF1 for NF1 and PTPN11 for NS. Heterozygous mutations or deletions of NF1 were identified in all patients, while no PTPN11 mutation was found. The NF1 mutation segregated with the phenotype in both familial cases. These results support the hypothesis that variable phenotypes of the NF1-NS spectrum represent variants of NF1 in the majority of cases. Constitutive deregulation of the Ras pathway either through activating mutations of PTPN11 or through haploinsufficiency of neurofibromin, which acts as a Ras-inactivating GTP-ase, is probably the common pathogenetic mechanism explaining the phenotypic overlap of NS and NF1.

Genetic disorders of pigmentation

More than 127 loci are actually known to affect pigmentation in mouse when they are mutated. From embryogenesis to transfer of melanin to the keratinocytes or melanocytes survival, any defect is able to alter the pigmentation process. Many gene mutations are now described, but the function of their product protein and their implication in melanogenesis are only partially understood. Each genetic pigmentation disorder brings new clues in the understanding of the pigmentation process. According to the main genodermatoses known to induce hypo- or hyperpigmentation, we emphasize in this review the last advances in the understanding of the physiopathology of these diseases and try to connect, when possible, the mutation to the clinical phenotype.

Grouping of multiple-lentigines/LEOPARD and Noonan syndromes on the PTPN11 gene

Multiple-lentigines (ML)/LEOPARD (multiple lentigines, electrocardiographic-conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness) syndrome is an autosomal dominant condition--characterized by lentigines and café au lait spots, facial anomalies, cardiac defects--that shares several clinical features with Noonan syndrome (NS). We screened nine patients with ML/LEOPARD syndrome (including a mother-daughter pair) and two children with NS who had multiple café au lait spots, for mutations in the NS gene, PTPN11, and found, in 10 of 11 patients, one of two new missense mutations, in exon 7 or exon 12. Both mutations affect the PTPN11 phosphotyrosine phosphatase domain, which is involved in <30% of the NS PTPN11 mutations. The study demonstrates that ML/LEOPARD syndrome and NS are allelic disorders. The detected mutations suggest that distinct molecular and pathogenetic mechanisms cause the peculiar cutaneous manifestations of the ML/LEOPARD-syndrome subtype of NS.

Genetics of neurofibromatosis 1 and the NF1 gene

Neurofibromatosis 1 serves as a paradigm for understanding the principles of human genetics. The concepts of gene mutation, penetrance of the condition, variable clinical expressivity, mosaicism, age-dependent expression of clinical manifestations, and pleiotropy are evident in this autosomal dominant condition. The lack of genotype-phenotype correlation, except the whole-gene deletion phenotype, leads to speculation on modifiers of the haploinsufficient state of the NF1 gene product neurofibromin. The variant form of neurofibromatosis, neurofibromatosis Noonan's syndrome, suggests potential interaction of independent biochemical pathways. Identification of the NF1 gene led to the discovery of its role in ras signal transduction. Neurofibromin is a negative regulator of intracellular ras signaling. This observation now provides the framework for the development of rational medical therapies. In addition, knowledge of the molecular basis of the variable expression of clinical manifestations could provide better anticipatory guidance and more effective management of the medical complications that are associated with this condition.

Cardiovascular malformations and other cardiovascular abnormalities in neurofibromatosis 1

Although it is well recognized that a peripheral vasculopathy may occur in patients with neurofibromatosis 1 (NF1), it is unclear whether cardiovascular abnormalities are more common. We reviewed the frequency of cardiovascular abnormalities, in particular, cardiovascular malformations (CVMs), among 2322 patients with definite NF1 in the National Neurofibromatosis Foundation International Database from 1991-98. Cardiovascular malformations were reported in 54/2322 (2.3%) of the NF1 patients, only 4 of whom had Watson syndrome or NF1-Noonan syndrome. There was a predominance of Class II "flow" defects [Clark, 1995: Moss and Adams' Heart Disease in Infants, Children, and Adolescents Including the Fetus and Young Adult. p 60-70] (43/54, 80%) among the NF1 patients with CVMs. Pulmonic stenosis, that was present in 25 NF1 patients, and aortic coarctation, that occurred in 5, constitute much larger proportions of all CVMs than expected. Of interest was the paucity of Class I conotruncal defects (2 patients with tetralogy of Fallot), and the absence of atrioventricular canal, anomalous pulmonary venous return, complex single ventricle and laterality defects. Besides the 54 patients with CVMs, there were 27 patients with other cardiac abnormalities (16 with murmur, 5 with mitral valve prolapse, 1 with intracardiac tumor, and 5 with electrocardiogram abnormalities). No patient in this study had hypertrophic cardiomyopathy. There were 16 patients who had a peripheral vascular abnormality without an intracardiac CVM, plus an additional 4 patients among those with a CVM who also had a peripheral vascular abnormality.

Advances in the molecular genetics of congenital structural heart disease

Molecular genetic analyses have generated significant advances in our understanding of congenital heart disease. Techniques of genetic mapping with polymorphic microsatellites and fluorescence in situ hybridization (FISH) have provided informative tools for localization and identification of disease genes. Some cardiovascular diseases have proven to result from single gene defects. Others relate to more complex etiologies involving several genes and their interactions. Elucidation of the molecular genetic etiologies of congenital heart disease prompts consideration of DNA testing for cardiac disorders. Future integration of these diagnostic modalities with improved treatments may ultimately decrease morbidity and mortality from congenital heart diseases.

The diagnostic value of café-au-lait macules

Single café-au-lait macules (CALMs) are common in the pediatric population and in most children represent a normal finding. It is important to recognize whether the presence of multiple CALMs in a particular patient is normal or indicates an association with a multisystem disorder. This article addresses issues concerning the prevalence, genetics, and natural history of CALMs in the general population and reviews disorders in which CALMs are present as a characteristic trait.

Familial neurofibromatosis type 1 associated with an overgrowth syndrome resembling Weaver syndrome

The simultaneous occurrence of familial neurofibromatosis type 1 (NF1) and an overgrowth syndrome resembling Weaver syndrome was observed in two related cases (a mother and her son). NF1 was confirmed by molecular genetic analysis showing a large deletion at 17q11.2, encompassing the entire NF1 gene. The other symptoms in the two cases were similar to the features reported in Weaver syndrome. Although the combination of NF1 and an overgrowth syndrome resembling Weaver syndrome in this family may be fortuitous, we favour the hypothesis that the deletion of the entire gene has caused this combined phenotype. Possible pathogenetic mechanisms are discussed. The observation suggests a relation between NF1 with an extraordinarily large gene deletion and a Weaver(-like) syndrome. This warrants investigation for deletions in the 17q11.2 region in Weaver(-like) syndrome patients.

Cardio-facio-cutaneous (CFC) syndrome--a distinct entity? Report of three patients demonstrating the diagnostic difficulties in delineation of CFC syndrome

We report on three patients with probable cardio-facio-cutaneous (CFC) syndrome. They present clinical findings of this condition such as: growth failure, heart defects, typical craniofacial appearance, ectodermal abnormalities, and developmental delay. We also give a detailed review of the previously published articles on CFC syndrome and discuss the differences between CFC, Noonan, and Costello syndromes. Other differential diagnoses are considered.

Multiple lentigines syndrome (LEOPARD syndrome or progressive cardiomyopathic lentiginosis)

The multiple lentigines syndrome is an autosomal dominant condition which has many similarities to Noonan syndrome, except in the most striking feature from which its name is derived. The less neutral but very apt mnemonic, LEOPARD syndrome, was first used by Gorlin et al to whom the major debt in the definition of this syndrome lies, that is, Lentigines, ECG abnormalities, Ocular hypertelorism/Obstructive cardiomyopathy, Pulmonary valve stenosis, Abnormalities of genitalia in males, Retardation of growth, and Deafness. Not previously included in the mnemonic is cardiomyopathy which is an important feature because it is associated with significant mortality.

Exclusion of allelism of Noonan syndrome and neurofibromatosis-type 1 in a large family with Noonan syndrome-neurofibromatosis association

A large four-generation family with Noonan syndrome (NS) and neurofibromatosis-type 1 (NF1) was studied for clinical association between the two diseases and for linkage analysis with polymorphic DNA markers of the NF1 region in 17q11.2. Nonrandom segregation between NS and NF1 phenotypes was observed. Neurofibromatosis was tightly linked to NF1 markers, whereas Noonan syndrome was found not be allelic to NF1. These results suggest that two mutations at two independent but closely linked loci are the cause of neurofibromatosis-Noonan syndrome (NF-NS) association in this family.

Molecular genetics of neurofibromatosis type 1 (NF1)

Neurofibromatosis type 1 (NF1), also called von Recklinghausen disease or peripheral neurofibromatosis, is a common autosomal dominant disorder characterised by multiple neurofibromas, café au lait spots, and Lisch nodules of the iris, with a variable clinical expression. The gene responsible for this condition, NF1, has been isolated by positional cloning. It spans over 350 kb of genomic DNA in chromosomal region 17q11.2 and encodes an mRNA of 11-13 kb containing at least 59 exons. NF1 is widely expressed in a variety of human and rat tissues. Four alternatively spliced NF1 transcripts have been identified. Three of these transcript isoforms (each with an extra exon: 9br, 23a, and 48a, respectively) show differential expression to some extent in various tissues, while the fourth isoform (2.9 kb in length) remains to be examined. The protein encoded by NF1, neurofibromin, has a domain homologous to the GTPase activating protein (GAP) family, and downregulates ras activity. The identification of somatic mutations in NF1 from tumour tissues strongly supports the speculation that NF1 is a member of the tumour suppressor gene family. Although the search for mutations in the gene has proved difficult, germline mutation analysis has shown that around 82% of all the fully characterised NF1 specific mutations so far predict severe truncation of neurofibromin. Further extensive studies are required to elucidate the gene function and the mutation spectrum. This should then facilitate the molecular diagnosis and the development of new therapy for the disease.

Noonan syndrome with café-au-lait spots and multiple lentigines syndrome are not linked to the neurofibromatosis type 1 locus

Noonan syndrome, multiple lentigines syndrome (LEOPARD syndrome), Watson syndrome and neurofibromatosis type 1 share certain clinical manifestations. We present a linkage analysis using microsatellite markers located in the neurofibromatosis type 1 region at 17q11 in a family with Noonan syndrome and café-au-lait spots and in another family with multiple lentigines syndrome. No linkage of the disease to the neurofibromatosis type 1 locus was found in the families investigated. On the basis of our results, we suggest that neither familial multiple lentigines syndrome nor Noonan syndrome is caused by a defect in the neurofibromatosis type 1 gene.

Evidence of central nervous system involvement in Watson syndrome

In 1967, Watson described 3 families with an autosomal dominant condition characterized by pulmonary valvular stenosis, café-au-lait sports, and short stature. Presumed hamartomatous lesions have been observed in neurofibromatosis type I, but they were not reported to date in Watson syndrome. We report another family with Watson syndrome, in which 1 patient manifested increased intensity T2-weighted lesions on magnetic resonance imaging similar to those occurring in neurofibromatosis type I and possibly hamartomas. This finding demonstrates the overlap between neurofibromatosis type I and Watson syndrome and supports the hypothesis that those conditions are allelic or, less likely, that the gene that determines the Watson phenotype is very closely linked to the neurofibromatosis type I locus.

Anaesthesia for caesarean section in a patient with Watson's syndrome

Watson's syndrome is an uncommon genetic disorder whose features include mental retardation and pulmonary valvular stenosis. The purpose of this report is to describe one management strategy used successfully to anaesthetize a woman with this disorder who presented for Caesarean section. Epidural anaesthesia using 0.5% bupivacaine without epinephrine in 2-3 ml boluses to a total dose of 15 ml was administered over 30 min. Invasive haemodynamic monitoring in the form of arterial and central venous catheters were used to guide therapy and help ensure maternal and fetal well-being. Intravenous ketamine in doses of 10-20 mg every five minutes to a total dose of 245 mg (4.5 mg.kg-1) was used to overcome the patient's uncooperative nature and facilitate invasive procedures. Postoperative analgesia was provided using 3 mg epidural morphine. The patient was observed in the intensive care unit for the first postoperative day and experienced an uncomplicated intra- and postoperative course. We conclude that this technique represents a safe and effective method for anaesthetizing patients with this complicated problem for Caesarean section.

Molecular basis of neurofibromatosis type 1 (NF1): mutation analysis and polymorphisms in the NF1 gene

Neurobromatosis type 1 (NF1) is one of the commonest genetic disorders in humans. The gene for NF1 was cloned in 1990. The protein encoded by the gene (neurofibromin) has extensive sequence homology with GTPase-activating protein (GAP). Despite screening the whole coding region of the gene for large and medium size rearrangements and approximately 40% of the coding region of the gene for small alterations, only 45 germ-line mutations have been reported in more than 500 unrelated patients. Of these, 25 mutations involve small changes in the gene, of which 17 (68%) result in the formation of an inappropriate stop codon. A "hot spot" for mutations has not been identified. The high mutation rate at this locus and the general difficulty in identifying mutations are discussed. A complete understanding of the structure and function of the NF1 gene awaits further detailed studies of both naturally occurring and in vitro-generated mutations.

Tandem duplication within a neurofibromatosis type 1 (NF1) gene exon in a family with features of Watson syndrome and Noonan syndrome

Type 1 neurofibromatosis (NF1), Watson syndrome (WS), and Noonan syndrome (NS) show some overlap in clinical manifestations. In addition, WS has been shown to be linked to markers flanking the NF1 locus and a deletion at the NF1 locus demonstrated in a WS patient. This suggests either that WS and NF1 are allelic or that phenotypes arise from mutations in very closely linked genes. Here we provide evidence for the former by demonstrating a mutation in the NF1 gene in a family with features of both WS and NS. The mutation is an almost perfect in-frame tandem duplication of 42 bases in exon 28 of the NF1 gene. Unlike the mutations previously described in classical NF1, which show a preponderance of null alleles, the mutation in this family would be expected to result in a mutant neurofibromin product.

Multiple cutaneous granular cell tumors with systemic defects: a distinct entity?

BACKGROUND

The association between cutaneous granular cell tumors and systemic defects is extremely rare, this being the tenth case reported in the literature. The reported defects in the literature include lentiginosis, face and skull alterations, heart defects, muscular and neural pathologies, among other sporadic defects in other organs. The patients do not present visceral granular cell tumors.

CASE REPORT

An 11-year-old girl had 124 skin granular cell tumors associated with face and skull defects, pulmonary stenosis, EEG and other neurologic alterations, diffuse muscle hypotonia, and an excess of finger joint mobility.

CONCLUSIONS

The combination of multiple cutaneous granular cell tumors with repeated alterations in other organs seems to be more than simply coincidental, thus suggesting a syndromic separate entity.

Nosological considerations of the neurofibromatoses

We are on the threshold of evaluating the NF1 and NF2 loci with respect to variant forms of the neurofibromatoses. Genetic mapping of NF1, gene cloning and characterization of its encoded product, neurofibromin, provides a framework for the evaluation of the variant forms of NF. This may also apply to NF2 variant forms in the near future. The mapping approach in evaluating variant forms of NF should begin with the rigorous clinical assessment of familial cases whereby the establishment of genetic linkage in families with overlap syndromes might determine if either NF1, NF2, or a separate locus is involved in the phenotype. Conditions mapping to the NF1 locus could then be screened for mutations in hopes of identifying the etiologies of the variant forms of NF. Mutation identification should provide a molecular-based classification scheme for the variant forms of NF, now tentatively divided into alternative and related forms. It is expected that the nosology of the neurofibromatoses will most certainly change as more is learned of the NF1 and NF2 loci.

Absence of linkage of Noonan syndrome to the neurofibromatosis type 1 locus

Eleven families with Noonan syndrome in either two or three generations have been identified. Following the reports of subjects with features of both Noonan syndrome and neurofibromatosis type 1, these pedigrees have been studied using a number of probes at the neurofibromatosis type 1 locus (17q11). A significantly negative lod score was obtained with the intragenic probe NF1-C2, suggesting that the genes for Noonan syndrome and neurofibromatosis type 1 are not contiguous.

Watson syndrome: is it a subtype of type 1 neurofibromatosis?

Over 20 years ago, Watson described three families with a condition characterised by pulmonary valvular stenosis, café au lait patches, and dull intelligence. Short stature is an additional feature of this autosomal dominant condition. A fourth family with Watson syndrome has since been reported. We have had the opportunity to review members of three of these four families. The clinical phenotype of Watson syndrome has been expanded to include relative macrocephaly and Lisch nodules in the majority of affected subjects, and neurofibromas in one-third of family members. Because the additional clinical findings enhance the similarity between Watson syndrome and neurofibromatosis 1, molecular linkage studies have been performed using probes flanking the NF1 gene on chromosome 17. Probe HHH202 showed the tightest linkage to Watson syndrome with a maximum lod score of 3.59 at phi = 0.0 (95% confidence limits of phi = 0.0-0.15). This suggests either that Watson syndrome and neurofibromatosis 1 are allelic, or that there is a series of contiguous genes for pulmonary stenosis, neurocutaneous anomalies, short stature, and mental retardation on 17q.

'Leopard' syndrome

'Leopard' syndrome is a rare inherited disorder associated with a high prevalence of cardiac abnormalities. General anaesthesia for dental treatment in a patient who had cardiomyopathy and bizarre electrocardiographic abnormalities associated with this syndrome is described. A thorough cardiac assessment is advised in a patient with multiple lentigines, although no clinical symptoms or signs may be found. Even if no cardiac abnormality is found before it is better to re-assess the patient, since abnormalities may develop later. The assessment should be repeated if any abnormality was detected before but without clinical significance, since the disease is progressive and may progress more rapidly in some patients than in others.