A trinucleotide deletion in the transthyretin gene (delta V 122) in a kindred with familial amyloidotic polyneuropathy

A 63-year-old white man of Ecuadorian origin had a subarachnoid hemorrhage at age 57 followed by numbness and paresthesia in his lower extremities. He subsequently developed sexual impotence, alternating constipation and diarrhea, urinary frequency, and difficulty in walking. Rectal biopsy revealed amyloid deposits immunohistochemically reactive with antitransthyretin antisera. Direct DNA sequencing of the transthyretin gene of the patient showed a trinucleotide deletion in exon 4. This deletion resulted in the loss of one of two valines at position 121 or 122. DNA analysis on 11 family members at risk revealed four mutant gene carriers. Plasma transthyretin levels in the mutant gene carriers measured by nephelometry were very low. Peptide sequence analysis revealed that most of plasma transthyretin was normal with only a small amount of variant protein. This is the first report of a DNA deletion in the transthyretin gene. We speculate that the loss of valine in the carboxyl terminal region of the transthyretin monomer alters stability of the tetrameric protein, which leads to rapid clearance from the plasma and amyloid deposition in the tissue.     

Low penetrance in the long-QT syndrome: clinical impact

BACKGROUND: It is still currently held that most patients affected by the long-QT syndrome (LQTS) show QT interval prolongation or clinical symptoms. This is reflected by the assumption in linkage studies of a penetrance of 90%. We had previously suggested that a larger-than-anticipated number of LQTS patients might be affected without showing clinical signs. We have now exploited the availability of molecular diagnosis to test this hypothesis. METHODS AND RESULTS: We identified 9 families with "sporadic" cases of LQTS, ie, families in which, besides the proband, none of the family members had clinical signs of the disease. Mutation screening by conventional single-strand conformational polymorphism and sequencing was performed on DNA of probands and family members to identify mutation carriers. Of 46 family members considered on clinical grounds to be nonaffected, 15 (33%) were found instead to be gene carriers. Penetrance was found to be 25%. In these families, conventional clinical diagnostic criteria had a sensitivity of only 38% in correctly identifying carriers of the genetic defect. CONCLUSIONS: This study demonstrates that in some families, LQTS may appear with a very low penetrance, a finding with multiple clinical implications. The family members considered to be normal and found to be silent gene carriers are unexpectedly at risk of generating affected offspring and also of developing torsade de pointes if exposed to either cardiac or noncardiac drugs that block potassium channels. It is no longer acceptable to exclude LQTS among family members of definitely affected patients on purely clinical grounds. Conversely, it now appears appropriate to perform molecular screening in all family members of genotyped patients.     

Familial hypertrophic cardiomyopathy

Investigating the family consisted of 8 members authors confirmed the diagnosis of hypertrophic cardiomyopathy in 5 cases. Secondly clinical features and echocardiographic data were compared. The clinical symptoms were not proportional to the pattern of hypertrophy revealed by echocardiography. The most significant pattern of hypertrophy was registered in youngest patients most likely due to increased expression and penetration of responsible genes. Considering cardiomyopathy as an inherited disease authors find family screening as a key in understanding and management of the disease.     

Mutations in the gene for cardiac myosin-binding protein C and late-onset familial hypertrophic cardiomyopathy

BACKGROUND: Mutations in the gene for cardiac myosin-binding protein C account for approximately 15 percent of cases of familial hypertrophic cardiomyopathy. The spectrum of disease-causing mutations and the associated clinical features of these gene defects are unknown. METHODS: DNA sequences encoding cardiac myosin-binding protein C were determined in unrelated patients with familial hypertrophic cardiomyopathy. Mutations were found in 16 probands, who had 574 family members at risk of inheriting these defects. The genotypes of these family members were determined, and the clinical status of 212 family members with mutations in the gene for cardiac myosin-binding protein C was assessed. RESULTS: Twelve novel mutations were identified in probands from 16 families. Four were missense mutations; eight defects (insertions, deletions, and splice mutations) were predicted to truncate cardiac myosin-binding protein C. The clinical expression of either missense or truncation mutations was similar to that observed for other genetic causes of hypertrophic cardiomyopathy, but the age at onset of the disease differed markedly. Only 58 percent of adults under the age of 50 years who had a mutation in the cardiac myosin-binding protein C gene (68 of 117 patients) had cardiac hypertrophy; disease penetrance remained incomplete through the age of 60 years. Survival was generally better than that observed among patients with hypertrophic cardiomyopathy caused by other mutations in the genes for sarcomere proteins. Most deaths due to cardiac causes in these families occurred suddenly. CONCLUSIONS: The clinical expression of mutations in the gene for cardiac myosin-binding protein C is often delayed until middle age or old age. Delayed expression of cardiac hypertrophy and a favorable clinical course may hinder recognition of the heritable nature of mutations in the cardiac myosin-binding protein C gene. Clinical screening in adult life may be warranted for members of families characterized by hypertrophic cardiomyopathy.     

Liver transplantation in familial amyloid polyneuropathy. Case report and review of the literature

A 59-year old male of German origin noticed exercise-independent cardiac arrhythmia two years before admission. An alanine 47 transthyretin variant of Familial Amyloid Polyneuropathy with hypertrophic cardiomyopathy, peripheral sensory-motor polyneuropathy, I, degree AV heart block was diagnosed. To diminish production and deposition of mutant transthyretin and to prevent disease progression orthotopic liver transplantation was performed. Prior to transplant the patient complained of inappetence. Postoperatively, he received a chemically defined enteral nutrition regime that was discontinued after 30 months until return of appetite and weight gain indicated marked improvement. However, a duodenal biopsy still demonstrated amyloid deposits 24 months after transplantation. Echocardiographic findings remained unchanged. Neurologic examination showed an improvement of sensory-motor polyneuropathy with regression of electromyographic changes. Only traces of variant transthyretin were detectable in plasma samples taken 12 months after the operation. During the 3 year follow-up, no additional symptoms have occurred and progression of amyloidosis was prevented. Currently, orthotopic liver transplantation is the only specific treatment to prevent progression of familial amyloid polyneuropathy.     

Cerebral cysticercosis in Campina Grande, Paraíba--northern Brazil. Computerized tomography diagnosis importance

A woman with Noonan syndrome had clinical and haemodynamic features of restrictive cardiomyopathy. There was no ventricular hypertrophy on echocardiography but myocardial biopsies showed myocyte hypertrophy without pathological disarray. This case illustrates the overlap of the cardiac phenotypes of Noonan syndrome, restrictive cardiomyopathy, and hypertrophic cardiomyopathy.     

Familial amyloid polyneuropathy related to transthyretin mutation Val30 to Leu in a Japanese family

A rare variant transthyretin that has a leucine-for-valine substitution at position 30 was reported in a sporadic case of type 1 familial amyloid polyneuropathy (FAP). We found the same substitution in members of a Japanese family with FAP. Three individuals in this family had a guanine-to-cytosine mutation at the first base of codon 30 in exon 2. This family shows a direct link between a valine-to-leucine substitution at position 30 and type 1 FAP.     

Heart transplantation in children and young adults: early and intermediate-term results

The purpose of this article is to report our short- and intermediate-term follow-up of cardiac transplantation for congenital heart disease and cardiomyopathy in children (age greater than 6 months), adolescents, and young adults. Thirty patients (ages 8 months to 24 years) with end-stage heart failure have undergone cardiac transplantation in our program: 12 (40%) for postoperative end-stage heart failure, 9 (30%) as primary treatment for congenital heart disease, 5 (17%) for dilated cardiomyopathy, and 4 (13%) for restrictive/hypertrophic cardiomyopathy. Nineteen patients (63%) had undergone prior operations; 4 patients received transplants for failed Fontan procedures. Induction therapy with antithymocyte therapy was used routinely, and long-term immunosuppression was by cyclosporine and azathioprine alone. Rejection surveillance/diagnosis was based on echocardiographic criteria. Posttransplantation follow-up ranges from 3 to 78 months. Operative mortality was 3.3% (1/30). No patients have been diagnosed with either accelerated allograft atherosclerosis or posttransplantation lymphoproliferative disease. We conclude that cardiac transplantation may be performed with excellent early and intermediate-term results.     

Restrictive myocardiopathy in children

Four children, three males and one female, aged 1.5 months to 11 years, with restrictive cardiomyopathy are described. One had patent ductus arteriosus in association. Hepatomegaly, abnormal second heart sound and signs of pulmonary venous congestion in chest X-ray were the most consistent clinical findings. Diagnosis was based on echocardiographic findings, cardiac catheterization data and results of pathology. The most frequent echocardiographic sign was the enlargement of both atria but with the ventricles within normal size and normal systolic function. Abnormalities in second phase of the ventricular filling were recorded in 2D-echo Doppler and cardiac catheterization, where a dip and plateau morphology of ventricular tracings was recorded. Metabolic studies performed in two children were normal, and any child had hypereosinophilia. Two children died, one was lost for follow-up and another is asymptomatic. Remarks on medical and surgical management are made.     

Cardiomyopathy of limb-girdle muscular dystrophy

OBJECTIVES: This study sought to find an association between dilated cardiomyopathy and limb-girdle muscular dystrophy. BACKGROUND: Cardiomyopathy has been seen in various neuromuscular disorders, but it has not been recognized to be associated with limb-girdle muscular dystrophy. METHODS: We investigated three sisters with well documented limb-girdle dystrophy and congestive heart failure by the 3rd decade of life. All underwent noninvasive evaluation of left ventricular systolic function by both echocardiography and radionuclide scanning, and one also had cardiac catheterization. Deoxyribonucleic acid (DNA) linkage analysis was performed in these affected subjects and in the unaffected family members, and DNA was extracted from mononuclear cells with primer sequences for three chromosome 13q microsatellite markers. RESULTS: The parents had no evidence of clinical disease, but all three sisters had echocardiographic evidence of dilated cardiomyopathy. The sister with additional evidence of left ventricular dysfunction of cardiac catheterization had no coronary artery disease. The affected subjects had the same paternal allele for three potential markers of limb-girdle muscular dystrophy but different maternal alleles. The very small family size did not permit statistical confirmation or refutation of linkage for chromosome 13q markers. CONCLUSIONS: Demonstrable cardiomyopathy accompanying limb-girdle muscular dystrophy and its probable genetic associations require continued investigation by anticipating the cardiomyopathy in limb-girdle muscular dystrophy.     

Mutations of ret-proto-oncogene in thyroid medullary carcinoma

OBJECTIVE: To determine the importance of the molecular-genetic demonstration of germ-line mutation in the ret protooncogene for therapeutic measures in sporadic and hereditary medullary thyroid carcinoma (MTC). PATIENTS AND METHODS: Several molecular-genetic tests were performed on DNA of 35 families with hereditary and 81 patients with the sporadic form of MTC (isolation of genomic DNA; PCR amplification; DNA sequencing: demonstration of mutation in codon 918 with restriction enzyme FOK 1). RESULTS: A disease risk was demonstrated in 178 individuals among the 35 families, 159 of whom were investigated by molecular-genetic tests: 84 family members were found to be gene carriers. Germ-line mutation had already been suspected on clinical grounds in 76% of the carriers, 24% being discovered in a presymptomatic stage. Six children among the latter were treated prophylactically by thyroidectomy, histological evidence of C-cell hyperplasia being found in all of them, microcarcinomas in three of the older children. There were four patients among the non-carriers on whom thyroidectomy had been performed previously because of a false-positive pentagastrin-test; but germ-line mutation was now excluded. In one family, with familial MTC in two brothers, no mutation in ret-proto-oncogene has been demonstrated. The members of this family must now, as used to be routine, undergo a pentagastrin-test. Three of the 81 patients with "sporadic" MTC had a germ-line mutation, presumably a new one. CONCLUSION: Molecular-genetic tests have further improved the management of families with hereditary MTC and they thus take first place among essential diagnostic procedures. The diagnosis of sporadic MTC can be confirmed by excluding germ-line mutation in the ret-proto-oncogene.     

Early expression of a malignant phenotype of familial hypertrophic cardiomyopathy associated with a Gly716Arg myosin heavy chain mutation in a Korean family

The clinical course and prognosis of familial hypertrophic cardiomyopathy (HCM) are different according to the type of mutation in the genes for sarcomere proteins. It has been disputed that a mutation, which occurs at a functionally important region in the sarcomere proteins, may increase the penetrance and expressivity of the disease. We searched for a causative mutation in an HCM family, which is characterized by early expression of clinical phenotype, high incidence of sudden death at young ages, and progressive heart failure in adults. Among the 32 family members in 4 generations, 13 were affected; 4 died suddenly before age 16, 2 children have already had full expression of the cardiac hypertrophy, and other adults have either progressive heart failure or poor left ventricular systolic functions. PCR-SSCP (polymerase chain reaction-single strand confirmation polymorphism) analysis of genomic DNAs isolated from peripheral blood leukocytes of the family members identified a Gly716Arg mutation in the cardiac beta-myosin heavy chain gene, which was cosegregated with the clinical phenotype. The mutation is localized near a functionally important site of the myosin heavy chain, the 2 active thiols, which contribute to the adenosine triphosphatase activity of myosin S1. This family provides further evidence that the mutation, which occurs at a functionally important site of the myosin heavy chain, is associated with the high penetrance and early expression of HCM.     

Codon 102 of the cardiac troponin T gene is a putative hot spot for mutations in familial hypertrophic cardiomyopathy

BACKGROUND: Familial hypertrophic cardiomyopathy is a phenotypically and genetically heterogeneous disease. In some families, the disease is linked to the CMH2 locus on chromosome 1q3, in which the cardiac troponin T gene (TNNT2) has been identified as the disease gene. The mutations found in this gene appear to be associated with incomplete penetrance and poor prognosis. Because mutational hot spots offer unique possibilities for analysis of genotype-phenotype correlations, new missense mutations that could define such hot spots in TNNT2 were looked for in unrelated French families with familial hypertrophic cardiomyopathy. METHODS AND RESULTS: Family members were genotyped with microsatellite markers to detect linkage to the four known disease loci. In family 715, analyses showed linkage to CMH2 only. To accurately position potential mutations on TNNT2, its partial genomic organization was established. Screening for mutations was performed by single-strand conformation polymorphism analysis and sequencing. A new missense mutation, Arg102Leu, was identified in affected members of family 715 because of a G-->T transversion located in the 10th exon of the gene. Penetrance of this new mutation is complete; echocardiographic data show a wide range of hypertrophy; and there was no sudden cardiac death in this family. CONCLUSIONS: The codon 102 of the TNNT2 gene is a putative mutational hot spot in familial hypertrophic cardiomyopathy and is associated with phenotypic variability. Analysis of more pedigrees carrying mutations in this codon is necessary to better characterize the clinical and prognostic implications of TNNT2 mutations.     

Serum amyloid P component scintigraphy in familial amyloid polyneuropathy: regression of visceral amyloid following liver transplantation

Familial amyloid polyneuropathy (FAP) associated with transthyretin (TTR) mutations is the commonest type of hereditary amyloidosis. Plasma TTR is produced almost exclusively in the liver and orthotopic liver transplantation is the only available treatment, although the clinical outcome varies. Serum amyloid P component (SAP) scintigraphy is a method for identifying and quantitatively monitoring amyloid deposits in vivo, but it has not previously been used to study the outcome of visceral amyloid deposits in FAP following liver transplantation. Whole body scintigraphy following injection of iodine-123 labelled SAP was performed in 17 patients with FAP associated with TTR Met30 and in five asymptomatic gene carriers. Follow-up studies were performed in ten patients, eight of whom had undergone orthotopic liver transplantation 1-5 years beforehand. There was abnormal uptake of 123I-SAP in all FAP patients, including the kidneys in each case, the spleen in five cases and the adrenal glands in three cases. Renal amyloid deposits were also present in three of the asymptomatic carriers. Follow-up studies 1-5 years after liver transplantation showed that there had been substantial regression of the visceral amyloid deposits in two patients and modest improvement in three cases. The amyloid deposits were unchanged in two patients. In conclusion, 123I-SAP scintigraphy identified unsuspected visceral amyloid in each patient with FAP due to TTR Met30. The universal presence of renal amyloid probably underlies the high frequency of renal failure that occurs in FAP following liver transplantation. The variable capacity of patients to mobilise amyloid deposits following liver transplantation may contribute to their long-term clinical outcome.     

The apolipoprotein E epsilon 4 allele does not influence the clinical expression of the amyloid precursor protein gene codon 693 or 692 mutations

In 31 symptomatic and 5 asymptomatic carriers of the amyloid precursor protein (APP) gene codon 693 mutation, 10 family members without mutation, and 5 carriers of the APP gene codon 692 mutation (3 with early-onset Alzheimer dementia, 2 with cerebral hemorrhage), a high frequency of the apolipoprotein E epsilon 4 allele was found. Age at onset, age at death, occurrence of dementia, and number of strokes did not differ between APP gene mutation carriers with or without epsilon 4 allele, showing that the clinical expression of these APP mutations is not influenced by the apolipoprotein E gene.     

Comparative stability and clearance of [Met30]transthyretin and [Met119]transthyretin

[Met119]Transthyretin has been described as a non-amyloidogenic transthyretin variant. In Portugal, it has also been found in compound heterozygotic individual carriers of [Met30]transthyretin, the most prevalent variant associated with familial amyloidotic polyneuropathy. In these individuals, the evolution of the disease seems to be more benign than in typical [Met30]transthyretin carriers, suggesting a protective effect of [Met119]transthyretin on the pathogenic effects of [Met30]transthyretin. To study the mechanisms of this protective effect, we performed comparative in vivo clearance studies. Heterotetrameric [Met119]transthyretin showed a slower clearance, whereas homotetrameric [Met30]transthyretin presented a faster clearance. These data correlate with the relative TTR levels present in carriers of these mutations. Comparative analyses of the resistance to dissociation into monomers of serum transthyretin by 4M urea isoelectric focusing suggested a higher tetrameric stability of transthyretin in [Met119]transthyretin carriers, in contrast to a lower stability in [Met30]transthyretin carriers. The compound heterozygotes presented a pattern similar to the normal individuals. Our results suggest that the protective clinical effect of the Met119 mutation possibly involves the stabilisation of the tetrameric structure of transthyretin. Whether this behaviour correlates with the different metabolism found for the two variants is not known. The approaches reported here open some possibilities for the study and development of future therapeutic agents of familial amyloidotic polyneuropathy.     

Physical and serologic examinations of foals at 30 and 45 days of age for early diagnosis of Rhodococcus equi infection on endemically infected farms

OBJECTIVE: To evaluate results of physical and serologic examinations of foals at 30 and 45 days of age on 3 types of farms with various prevalences of clinical disease (endemic, sporadic, none) caused by Rhodococcus equi and to determine whether evaluations were helpful in early diagnosis and control of the disease. DESIGN: Prospective cohort study. ANIMALS: 144 foals at 30 and 45 days of age. PROCEDURE: During a 2-year period, 36 foals on farms at which R equi infection was endemic, 71 foals on farms at which the disease was sporadically detected, and 37 foals on farms without the disease were examined by means of auscultation of lungs, serum biochemical and hematologic analyses, and determination of antibody titers against R equi, using ELISA. Transtracheal aspirates were obtained from 14 of 32 foals that had clinical signs of disease and 7 of 41 seropositive foals that did not have clinical signs of disease. RESULTS: Prevalences of respiratory tract disease and seropositive conversion rates for 45-day-old foals on endemically and sporadically infected farms were significantly higher than on farms without the disease. Rhodococcus equi was isolated from tracheal aspirates of seropositive foals, even when clinical signs were not evident. CLINICAL IMPLICATIONS: Physical and serologic examinations of foals at 30 and 45 days of age were useful for early diagnosis of R equi infection, especially for foals on farms at which the disease was endemic.     

Molecular basis of phenylketonuria in Venezuela: presence of two novel null mutations

We describe clinical, biochemical, and molecular studies on a Taiwanese family with X-linked recessive bulbospinal neuronopathy. There were three probands and five female carriers among the 23 members examined. The clinical manifestations included progressive muscle weakness, diffuse fasciculation, postural tremor, muscle cramps, dysarthria, dysphagia, diabetes, and gynecomastia. Phenotypic expression varied among the affected subjects. Two carriers also had postural tremor and perioral fasciculation. Endocrine tests were normal except for a mild increase in serum testosterone and/or growth hormone in one patient and one carrier. Type IV hyperlipoproteinemia was observed in two patients, one carrier, and one healthy offspring. Molecular genetic studies confirmed elongation of the CAG triplet repeat in exon 1 of the gene for the androgen receptor. Sequence analysis showed that there were 42 to 43 CAG repeats in the three probands and 42 to 45 in the five carriers. The mutant allele had a tendency to increase by one or two repeats from one generation to the next. The length of CAG repeats at which the mutant allele became unstable was shorter in our family than in previous reports. The normal allele was also unstable and had a tendency to shrink by one of five repeats during transmission. These findings suggest that the number of CAG triplet repeats is variable in both the mutant and normal alleles.     

Thin GBM nephropathy: premature glomerular obsolescence is associated with hypertension and late onset renal failure

Thin glomerular basement membrane (GBM) nephropathy, also called familial benign hematuria, is characterized by chronic hematuria and uniform thinning of the lamina densa of the glomerular basement membrane. It generally holds an excellent renal prognosis. Alport syndrome in early stages can also show attenuation of the GBM; conversely, renal insufficiency has been reported in familial benign hematuria. To discern early Alport syndrome from thin GBM nephropathy, we carried out a prospective epidemiological study in which 19 normotensive and non-azotemic adult patients with chronic microscopic (18 of 19) and macroscopic (1 of 19) hematuria and biopsy-proven thin GBM nephropathy were followed for a median of 12 years (range 9 to 15 years). Renal biopsies of thin GBM patients at entry showed an increased incidence of focal global glomerulosclerosis when compared to disease controls as IgA nephropathy (P = 0.047) and normal renal tissue (P = 0.0075). All renal biopsies showed the presence of the Goodpasture antigen when tested immunohistochemically. Presence of Alport syndrome was excluded clinically as none of the patients had complaints of hearing loss or abnormalities by audiography and ophthalmology. At the end of follow-up, the incidence of hypertension in thin GBM nephropathy (35%) exceeded that of healthy clinical controls (P = 0.048), and one hypertensive patient developed mild renal failure. In the normotensive patients, the glomerular filtration rate at follow-up as measured by inulin clearance was reduced in three out of seven; these were over 50 years of age. Although no family members were known to have renal disease at inclusion, within four families six elderly first degree relatives had developed unexplained renal insufficiency at the end of follow-up. Thus, thin GBM nephropathy predisposes to premature glomerular obsolescence, leading in time to increased incidences of hypertension and late onset renal insufficiency.     

The predictive value of electrodiagnostic studies in carpal tunnel syndrome

In recent years, electrodiagnostic studies have become an expected component in the work up and evaluation of carpal tunnel syndrome. We conducted a retrospective review of 460 carpal tunnel decompressions to determine whether the accuracy of diagnosis and the prediction of therapeutic outcome could be related to the positivity and severity of findings on preoperative electrical studies. The 349 patients (460 hands) were divided into two groups: group 1 consisted of hands with the clinical diagnosis of carpal tunnel syndrome but with normal electrodiagnostic studies (n = 62); in group 2 the hands had a clinical diagnosis of carpal tunnel syndrome with confirmatory electrodiagnostic studies (n = 398). The number and distribution of signs and symptoms of carpal tunnel syndrome were not statistically different between these two groups. There was not a statistically significant difference in the success rate of surgery or the incidence of complications. The similarities between these two groups suggests that the distinction between them (the positivity of electrodiagnostic studies) is an artificial one and that the clinical diagnosis of carpal tunnel syndrome is sufficient to predict the presence of the disease, as well as outcome of surgery. On the basis of these data, strict adherence to electrodiagnostic studies to confirm the diagnosis will exclude 13 percent of the patients with legitimate carpal tunnel syndrome from receiving appropriate therapy.