Application of Hereditary Renal Cell Carcinoma Risk Criteria to a Large Prospective Database.

AIMS: To evaluate the clinical impact of the Canadian criteria for identifying patients and families at risk for hereditary renal cell carcinoma (RCC). MATERIALS AND METHODS: The Canadian hereditary RCC risk criteria were applied to patients from 16 centres in the Canadian Kidney Cancer information system (CKCis) prospective database. The primary end point was the proportion of patients who met at least one criterion. RESULTS: Between January 2011 and May 2017, 8388 patients were entered in the database; 291 had inadequate risk data; 2827 (35%) met at least one criterion for genetic testing (at-risk population). Most (83%) met just one criterion. The criterion of non-clear cell histology contributed the largest proportion of at-risk patients (59%), followed by age ≤ 45 years (28%). Sixty-one patients had documentation of genetic testing, with 56 being classified at-risk (2% of at-risk). Twenty patients (35%) of the patients at risk and tested for hereditary RCC were found to harbour a germline mutation. CONCLUSIONS: Application of the Canadian hereditary RCC risk criteria to a large prospective database resulted in 35% of patients being identified at risk for hereditary RCC who could qualify for genetic testing. However, the true incidence of hereditary RCC in this population is unknown as most patients did not have documented genetic testing carried out and, thus, the sensitivity and specificity of the criteria cannot be determined. The low proportion of at-risk patients who underwent genetic testing is disappointing and highlights that there may be gaps in reporting, knowledge and/or barriers in access to genetic testing.

Utility of whole-exome sequencing for those near the end of the diagnostic odyssey: time to address gaps in care.

An accurate diagnosis is an integral component of patient care for children with rare genetic disease. Recent advances in sequencing, in particular whole-exome sequencing (WES), are identifying the genetic basis of disease for 25-40% of patients. The diagnostic rate is probably influenced by when in the diagnostic process WES is used. The Finding Of Rare Disease GEnes (FORGE) Canada project was a nation-wide effort to identify mutations for childhood-onset disorders using WES. Most children enrolled in the FORGE project were toward the end of the diagnostic odyssey. The two primary outcomes of FORGE were novel gene discovery and the identification of mutations in genes known to cause disease. In the latter instance, WES identified mutations in known disease genes for 105 of 362 families studied (29%), thereby informing the impact of WES in the setting of the diagnostic odyssey. Our analysis of this dataset showed that these known disease genes were not identified prior to WES enrollment for two key reasons: genetic heterogeneity associated with a clinical diagnosis and atypical presentation of known, clinically recognized diseases. What is becoming increasingly clear is that WES will be paradigm altering for patients and families with rare genetic diseases.

Deletion of MAP2K2/MEK2: a novel mechanism for a RASopathy?

RASopathies are a class of genetic syndromes caused by germline mutations in genes encoding Ras/mitogen-activated protein kinase (Ras/MAPK) pathway components. Cardio-facio-cutaneous (CFC) syndrome is a RASopathy characterized by distinctive craniofacial features, skin and hair abnormalities, and congenital heart defects caused by activating mutations of BRAF, MEK1, MEK2, and KRAS. We define the phenotype of seven patients with de novo deletions of chromosome 19p13.3 including MEK2; they present with a distinct phenotype but have overlapping features with CFC syndrome. Phenotypic features of all seven patients include tall forehead, thick nasal tip, underdeveloped cheekbones, long midface, sinuous upper vermilion border, tall chin, angular jaw, and facial asymmetry. Patients also have developmental delay, hypotonia, heart abnormalities, failure to thrive, obstructive sleep apnea, gastroesophageal reflux and integument abnormalities. Analysis of epidermal growth factor-stimulated fibroblasts revealed that P-MEK1/2 was ∼50% less abundant in cells carrying the MEK2 deletion compared to the control. Significant differences in total MEK2 and Sprouty1 abundance were also observed. Our cohort of seven individuals with MEK2 deletions has overlapping features associated with RASopathies. This is the first report suggesting that, in addition to activating mutations, MEK2 haploinsufficiency can lead to dysregulation of the MAPK pathway.

A comparative neuropsychological test battery differentiates cognitive signatures of Fragile X and Down syndrome.

BACKGROUND: Standardised neuropsychological and cognitive measures present some limitations in their applicability and generalisability to individuals with intellectual disability (ID). Alternative approaches to defining the cognitive signatures of various forms of ID are needed to advance our understanding of the profiles of strengths and weaknesses as well as the affected brain areas. AIM: To evaluate the utility and feasibility of six non-verbal comparative neuropsychological (CN) tasks administered in a modified version of the Wisconsin General Test Apparatus (WGTA) to confirm and extend our knowledge of unique cognitive signatures of Fragile X syndrome (FXS) and Down syndrome (DS). METHOD: A test battery of CN tasks adapted from the animal literature was administered in a modified WGTA. Tasks were selected that have established or emerging brain-behaviour relationships in the domains of visual-perceptual, visual-spatial, working memory and inhibition. RESULTS: Despite the fact that these tasks revealed cognitive signatures for the two ID groups, only some hypotheses were supported. Results suggest that whereas individuals with DS were relatively impaired on visual-perceptual and visual-spatial reversal learning tasks they showed strengths in egocentric spatial learning and object discrimination tasks. Individuals with FXS were relatively impaired on object discrimination learning and reversal tasks, which was attributable to side preferences. In contrast, these same individuals exhibited strengths in egocentric spatial learning and reversal tasks as well as on an object recognition memory task. Both ID groups demonstrated relatively poor performance for a visual-spatial working memory task. CONCLUSION: Performance on the modified WGTA tasks differentiated cognitive signatures between two of the most common forms of ID. Results are discussed in the context of the literature on the cognitive and neurobiological features of FXS and DS.

Syndrome of coronal craniosynostosis, Klippel-Feil anomaly, and sprengel shoulder with and without Pro250Arg mutation in the FGFR3 gene.

A unique Pro250Arg point mutation in fibroblast growth factor receptor 3 (FGFR3) was initially reported by Bellus et al. [1996: Nat Genet 14:174-176] and the phenotype subsequently by Muenke et al. [1997: Am J Hum Genet 60:555-564], Reardon et al. [1997: J Med Genet 34:632-636], and Graham et al. [1998: Am J Med Genet 77:322-329]. These authors emphasized the pleiotropic nature of this form of coronal craniosynostosis, including brachydactyly with carpal and/or tarsal coalitions, with other anomalies at lower frequency. We report on a family with autosomal dominant coronal synostosis, segmentation and fusion anomalies of the vertebra and ribs, and Sprengel shoulder due to the Pro250Arg mutation. We also report a single case with an identical phenotype without the mutation.

Further evidence for genetic heterogeneity in familial hemophagocytic lymphohistiocytosis (FHLH).

Familial hemophagocytic lymphohistiocytosis (FHLH; MIM #267700) is an autosomal recessive disorder of immune regulation characterized by fever, hepatosplenomegaly, and cytopenia that is fatal without bone marrow transplantation. Recent studies have suggested the existence of FHLH loci at 9q21.3-22 and t0q21-22 in Asian and European/African/Australian families, respectively. We studied two unrelated Canadian families in which first cousins were affected with FHLH. In an effort to localize the causative gene, we completed a genome-wide screen for homozygosity by descent by using an automated system to genotype 400 highly polymorphic dinucleotide repeat markers covering the genome with an average resolution of 10 centiMorgans (cM). We identified a total of three candidate loci that met the combined criteria for homozygosity by descent in one family and shared maternal alleles in the other family. One of these, D9S1690, had a cytogenetic localization (9q22.33) proximal to a previously reported inversion of chromosome 9 in an FHLH patient. However, additional closely linked flanking markers within 1-2 cM of all three candidates did not conform to the criteria for linkage in either family. Similarly, we excluded the linked 9q21.3-q22 and 10q21-22 regions recently reported in Asian and European/African/Australian families, respectively. The two families were then analyzed independently to encompass the possibility that they were segregating separate genes. Six additional candidate loci were identified on the basis of homozygosity for the same allele in all affected members of one family, but further analysis of closely linked flanking markers did not demonstrate similar homozygosity. Our data provide further evidence of genetic heterogeneity in FHLH and suggest the existence of at least a third locus for this disease.

Congenital cholesteatoma and malformations of the facial nerve: rare manifestations of the BOR syndrome.

We describe a 14-month-old girl with unilateral congenital cholesteatoma and anomalies of the facial nerve in addition to the more common branchial arch, otic, and renal malformations comprising the branchio-oto-renal (BOR) syndrome. Her mother also has the BOR syndrome and unilateral duplication of the facial nerve. This is the first study of a BOR patient with congenital cholesteatoma and the second family in which cholesteatoma and anomalies of the facial nerve are described in patients with the BO/BOR syndrome. We review the congenital cholesteatoma literature and discuss hypotheses for the pathogenesis of this entity in light of this new report.

Congenital insensitivity to pain with anhidrosis: novel mutations in the TRKA (NTRK1) gene encoding a high-affinity receptor for nerve growth factor.

Congenital insensitivity to pain with anhidrosis (CIPA) is characterized by recurrent episodes of unexplained fever, anhidrosis (inability to sweat), absence of reaction to noxious stimuli, self-mutilating behavior, and mental retardation. Human TRKA encodes a high-affinity tyrosine kinase receptor for nerve growth factor (NGF), a member of the neurotrophin family that induces neurite outgrowth and promotes survival of embryonic sensory and sympathetic neurons. We have recently demonstrated that TRKA is responsible for CIPA by identifying three mutations in a region encoding the intracellular tyrosine kinase domain of TRKA in one Ecuadorian and three Japanese families. We have developed a comprehensive strategy to screen for TRKA mutations, on the basis of the gene's structure and organization. Here we report 11 novel mutations, in seven affected families. These are six missense mutations, two frameshift mutations, one nonsense mutation, and two splice-site mutations. Mendelian inheritance of the mutations is confirmed in six families for which parent samples are available. Two mutations are linked, on the same chromosome, to Arg85Ser and to His598Tyr;Gly607Val, hence, they probably represent double and triple mutations. The mutations are distributed in an extracellular domain, involved in NGF binding, as well as the intracellular signal-transduction domain. These data suggest that TRKA defects cause CIPA in various ethnic groups.

Dyskeratosis congenita: an autosomal recessive variant.

We describe a woman with dyskeratosis congenita (DKC), microcephaly, and a purple discoloration of the tongue. The latter findings are not commonly described in males with DKC, have been reported in another female patient with this condition, and may represent the phenotype of an autosomal recessive entity of DKC. Results of X chromosome inactivation studies did not support X-linked DKC in our family. The additional findings of an affected brother and parental consanguinity support the hypothesis of autosomal recessive inheritance.

Germline PTEN mutation in a family with Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome.

Clinical overlap between Cowden disease and Bannayan-Riley-Ruvalcaba syndrome has rarely been described and identical germline mutations in the PTEN gene have been demonstrated in a few families with Cowden disease and some cases of Bannayan-Riley-Ruvalcaba syndrome. We report on a mother with Cowden disease and a son with Bannayan-Riley-Ruvalcaba syndrome. Mutation analysis of the PTEN gene demonstrated a heterozygous nonsense mutation R130X in both individuals. This might suggest that Cowden disease and Bannayan-Riley-Ruvalcaba syndrome are one causal entity.

King syndrome: further clinical variability and review of the literature.

The King syndrome is characterized by a Noonan-like phenotype, the presence of a nonspecific myopathy and a predisposition to malignant hyperthermia. In some families, mild physical manifestations of the phenotype and/or elevated serum creatine phosphokinase (CPK) in relatives suggest the presence of an autosomal dominant myopathy with variable expressivity. We summarize the cases of 14 previously reported patients and describe a new patient, a 7-year-old girl, with the King syndrome and the unique findings of diaphragmatic eventration, tethered spinal cord, and severe paucity of type 2 skeletal muscle fibers. It has been proposed that the King syndrome represents a common phenotype that may result from several different slowly progressive congenital myopathies. This hypothesis, and the phenotypic overlap between the King and Noonan syndromes are discussed in light of the findings in this new patient.

Absence of PTEN/MMAC1 germ-line mutations in sporadic Bannayan-Riley-Ruvalcaba syndrome.

Bannayan-Riley-Ruvalcaba syndrome (BRRS) is a rare hamartomatous polyposis condition with features of macrocephaly, intestinal juvenile polyposis, developmental delay, lipomas, and pigmentation spots of the male genitalia. An autosomal dominant pattern of inheritance exists in some families, but others appear as sporadic cases. Germ-line mutations in PTEN, a tyrosine phosphatase and putative tumor suppressor gene, have been demonstrated in two families with BRRS, and chromatin loss at the PTEN gene locus on chromosome 10q23 has been demonstrated in two BRRS patients. Germ-line mutations in PTEN have also been described in Cowden disease and in a small number of patients with juvenile polyposis syndrome. In an attempt to assess the nature of PTEN mutations in BRRS, we analyzed three sporadic BRRS patients for chromosome 10q23 deletion or PTEN germ-line mutations. All 3 patients demonstrated no loss of parental alleles at 15 chromosome 10q23 markers that encompassed the region of PTEN. In addition, analysis of mRNA and genomic DNA revealed no nonsense, missense, or insertion/deletion mutations of PTEN. Thus, other mechanisms besides mutation of PTEN must have occurred to cause BRRS in these patients. We speculate that BRRS and juvenile polyposis syndrome may have a heterogeneous etiology to cause their syndromes.

Gonadal mosaicism in a family with adrenoleukodystrophy: molecular diagnosis of carrier status among daughters of a gonadal mosaic when direct detection of the mutation is not possible.

Adrenoleukodystrophy is a severe, X-linked neurological disease that has been shown to be linked to DNA markers from Xq28. We tested several families with these markers and, in one family, found two apparent recombination events between DXS52 and the disease. Expansion of the study to include other tests and several others markers from Xq28 led us to conclude that recombination probably had not occurred and that, instead, the mutation in this family had a mitotic origin and that the grandmother was a gonadal mosaic. For genes that have been cloned, it is often possible to demonstrate the presence or absence of a specific mutation in such families and to determine carrier status on that basis. This is not possible when the gene has not been cloned. We therefore describe a method that can be employed by a molecular diagnostic laboratory to discriminate between people who inherit the same RFLP haplotype, with or without the mutation, from a parent with gonadal mosaicism in diseases where direct gene analysis is not yet possible.

Intraoperative straight-leg raising during laminectomy and disk excision for sciatica.

During lumbar disk excision for sciatica, doubts may occasionally arise as to the level of the lesion or the degree of involvement of the particular nerve root being observed. Following removal of the obstructing agent, can we be certain that liberation of the nerve root is complete? These anxieties can be dispelled by performing a straight-leg raising test bilaterally during the operation both before and after removal of the obstructing agent. The intraoperative straight-leg raising tests enable observations to be made as to the degree of nerve tension on the involved side as compared with tension on the uninvolved side; at the end of the operation, the tension on the involved side should be no more than the tension on the uninvolved side. When the straight-leg raising test is not being performed, it should be possible for the nerve root to be displaced to the midline of the spinal canal with ease.

Relationship of chemical structure and solvent to in vivo scintigraphic distribution patterns of 11C compounds. II. 11C aminonitriles.

The preparation and scintigraphic evaluation of the distribution patterns in dogs of a series of structurally related aminonitriles labeled with 11C is described. Carbon-11-HCN was collected in water containing carrier NaCN following 22 MeV proton bombardment of 99% N2 and 1% H2 gas mixture for 1 hr. Ten 11C alphaN-alkylaminophenylacetonitrile hydrochlorides and 12 11C alpha-N-arylaminoarylacetonitriles were prepared from 11C-NaCN and the corresponding Schiff base, Ar-CH=N-R(Ar). Those 11C aminonitriles that were administered intravenously in aqueous solution showed some initial accumulation of activity in the liver followed by diffuse whole-body distribution and some small accumulation in urine. Aqueous insoluble 11C aminonitriles, which were administered intravenously in ethanol, ether, or DMSO, showed variable initial partial retention of activity in the lungs with prominent accumulation of activity in liver and excretion in bile. Several of these compounds showed pronounced and rapid accumulation of activity in the brain. Such activity in the brain was largely cleared within 15 min. Concentration of activity in the cerebrospinal fluid following clearance from the brain was 30 times greater than blood and equivalent in concentration to that noted in bile 18 min after intravenous administration of 11C alpha-anilinophenylacetonitrile in ethanol. These results suggest the possible correlation of regional brain uptake of activity of certain 11C aminonitriles with regional brain perfusion. Use of these or similar materials could permit assessment of brain tissue morphology followed by scintigraphic imaging of the bulk flow characteristics of cerebrospinal fluid.